From 16f468142907aac96f1e8011662e49ff1fa4ee4c Mon Sep 17 00:00:00 2001
From: Maschga <88616799+Maschga@users.noreply.github.com>
Date: Fri, 3 Oct 2025 16:45:56 +0200
Subject: [PATCH] Tariffs: switch to 15m slots (#21162)

---
 assets/css/app.css                            |   3 +
 .../ChargingPlans/PlanRepeatingSettings.vue   |  18 +-
 .../ChargingPlans/PlanStaticSettings.vue      |  15 +-
 .../components/ChargingPlans/Preview.test.ts  |  47 ++--
 .../js/components/ChargingPlans/Preview.vue   |  59 +++--
 assets/js/components/Forecast/ActiveSlot.vue  |  10 +-
 assets/js/components/Forecast/Chart.vue       |   6 +-
 assets/js/components/Forecast/Details.vue     |  24 +-
 .../components/Loadpoints/SettingsModal.vue   |   4 +-
 assets/js/components/Optimize/ChargeChart.vue |  85 ++++++-
 assets/js/components/Optimize/PriceChart.vue  |  81 ++++++-
 assets/js/components/Optimize/SocChart.vue    | 214 ++++++++++++------
 .../Optimize/TimeSeriesDataTable.vue          |  18 +-
 assets/js/components/Site/Site.vue            |   2 +-
 .../js/components/Tariff/SmartTariffBase.vue  |  60 ++---
 assets/js/components/Tariff/TariffChart.vue   |  58 ++---
 assets/js/mixins/formatter.ts                 |   4 +-
 assets/js/types/evcc.ts                       |   5 +-
 assets/js/utils/forecast.test.ts              |  57 +++++
 assets/js/utils/forecast.ts                   |  23 ++
 assets/js/views/Optimize.vue                  |  13 --
 cmd/demo.yaml                                 |   6 +-
 core/site_optimizer.go                        |  77 ++-----
 core/site_optimizer_test.go                   | 181 +++++++--------
 go.mod                                        |   1 -
 go.sum                                        |   2 -
 i18n/de.json                                  |   4 +-
 i18n/en.json                                  |   4 +-
 server/http_loadpoint_handler.go              |  42 ++--
 tariff/config.go                              |   2 +-
 tariff/helper.go                              |   9 +-
 tariff/helper_test.go                         |   5 +
 tariff/slots.go                               |  67 ++++++
 tariff/slots_test.go                          | 186 +++++++++++++++
 tariff/tariff.go                              |  11 +-
 .../definition/tariff/demo-co2-forecast.yaml  |  20 +-
 .../definition/tariff/demo-dynamic-grid.yaml  | 117 ++++++++++
 .../tariff/demo-solar-forecast.yaml           |  26 ++-
 tests/plan.evcc.yaml                          |   2 +-
 39 files changed, 1093 insertions(+), 475 deletions(-)
 create mode 100644 assets/js/utils/forecast.test.ts
 create mode 100644 tariff/slots.go
 create mode 100644 tariff/slots_test.go
 create mode 100644 templates/definition/tariff/demo-dynamic-grid.yaml

diff --git a/assets/css/app.css b/assets/css/app.css
index fb45ac972..b2c0f2763 100644
--- a/assets/css/app.css
+++ b/assets/css/app.css
@@ -702,3 +702,6 @@ input::-webkit-date-and-time-value {
 		font-size: 0.875em;
 	}
 }
+.tabular {
+	font-variant-numeric: tabular-nums;
+}
diff --git a/assets/js/components/ChargingPlans/PlanRepeatingSettings.vue b/assets/js/components/ChargingPlans/PlanRepeatingSettings.vue
index 5c012b737..f02f2f54b 100644
--- a/assets/js/components/ChargingPlans/PlanRepeatingSettings.vue
+++ b/assets/js/components/ChargingPlans/PlanRepeatingSettings.vue
@@ -24,7 +24,7 @@
 					{{ $t("main.chargingPlan.time") }}
 				</label>
 			</div>
-			<div :class="showPrecondition ? 'col-2' : 'col-3'">
+			<div :class="showPrecondition ? 'col-3' : 'col-4'">
 				<label :for="formId('goal')">
 					{{ $t("main.chargingPlan.goal") }}
 				</label>
@@ -81,7 +81,7 @@
 					{{ $t("main.chargingPlan.goal") }}
 				</label>
 			</div>
-			<div :class="['col-7', showPrecondition ? 'col-lg-2' : 'col-lg-3', 'mb-2', 'mb-lg-0']">
+			<div :class="['col-7', showPrecondition ? 'col-lg-3' : 'col-lg-4', 'mb-2', 'mb-lg-0']">
 				<select
 					:id="formId('goal')"
 					v-model="selectedSoc"
@@ -114,7 +114,7 @@
 					{{ $t("main.chargingPlan.active") }}
 				</label>
 			</div>
-			<div class="col-2 col-lg-1 d-flex align-items-center">
+			<div class="col-3 col-lg-1 d-flex align-items-center">
 				<div class="form-check form-switch">
 					<input
 						:id="formId('active')"
@@ -129,16 +129,22 @@
 					/>
 				</div>
 			</div>
-			<div class="col-5 col-lg-2 d-flex align-items-center">
+			<div
+				class="col-4 col-lg-1 d-flex align-items-center justify-content-end justify-content-lg-start"
+			>
 				<button
 					v-if="showApply"
 					type="button"
-					class="btn btn-sm btn-outline-primary border-0 text-decoration-underline"
+					class="btn btn-sm btn-outline-primary border-0 text-decoration-underline text-truncate"
 					data-testid="repeating-plan-apply"
 					tabindex="0"
 					@click="update(true)"
 				>
-					{{ $t("main.chargingPlan.update") }}
+					<span class="d-lg-none">{{ $t("main.chargingPlan.update") }}</span>
+					<shopicon-regular-checkmark
+						size="s"
+						class="flex-shrink-0 d-none d-lg-block"
+					></shopicon-regular-checkmark>
 				</button>
 				<button
 					v-else
diff --git a/assets/js/components/ChargingPlans/PlanStaticSettings.vue b/assets/js/components/ChargingPlans/PlanStaticSettings.vue
index ef8057029..4eb743895 100644
--- a/assets/js/components/ChargingPlans/PlanStaticSettings.vue
+++ b/assets/js/components/ChargingPlans/PlanStaticSettings.vue
@@ -22,7 +22,7 @@
 					{{ $t("main.chargingPlan.time") }}
 				</label>
 			</div>
-			<div :class="showPrecondition ? 'col-2' : 'col-3'">
+			<div :class="showPrecondition ? 'col-3' : 'col-4'">
 				<label :for="formId('goal')">
 					{{ $t("main.chargingPlan.goal") }}
 				</label>
@@ -83,7 +83,7 @@
 					{{ $t("main.chargingPlan.goal") }}
 				</label>
 			</div>
-			<div :class="['col-7', showPrecondition ? 'col-lg-2' : 'col-lg-3', 'mb-2', 'mb-lg-0']">
+			<div :class="['col-7', showPrecondition ? 'col-lg-3' : 'col-lg-4', 'mb-2', 'mb-lg-0']">
 				<select
 					v-if="socBasedPlanning"
 					:id="formId('goal')"
@@ -145,18 +145,23 @@
 				</div>
 			</div>
 			<div
-				class="col-4 col-lg-2 d-flex align-items-center justify-content-end justify-content-lg-start"
+				class="col-4 col-lg-1 d-flex align-items-center justify-content-end justify-content-lg-start"
 			>
 				<button
 					v-if="dataChanged && !isNew"
 					type="button"
-					class="btn btn-sm btn-outline-primary border-0 text-decoration-underline"
+					class="btn btn-sm btn-outline-primary border-0 text-decoration-underline text-truncate"
 					data-testid="static-plan-apply"
 					:disabled="timeInThePast"
 					tabindex="0"
+					:aria-label="$t('main.chargingPlan.update')"
 					@click="update"
 				>
-					{{ $t("main.chargingPlan.update") }}
+					<span class="d-lg-none">{{ $t("main.chargingPlan.update") }}</span>
+					<shopicon-regular-checkmark
+						size="s"
+						class="flex-shrink-0 d-none d-lg-block"
+					></shopicon-regular-checkmark>
 				</button>
 			</div>
 		</div>
diff --git a/assets/js/components/ChargingPlans/Preview.test.ts b/assets/js/components/ChargingPlans/Preview.test.ts
index 2d0f67a58..ebce237e8 100644
--- a/assets/js/components/ChargingPlans/Preview.test.ts
+++ b/assets/js/components/ChargingPlans/Preview.test.ts
@@ -40,39 +40,34 @@ describe("basics", () => {
   });
 
   test("should return 39 slots", () => {
-    expect(result.length).eq(39);
+    expect(result.length).eq(192);
   });
 
   test("slots should be an hour apart", () => {
-    expect(result[0]!.startHour).eq(11);
-    expect(result[0]!.endHour).eq(12);
-    expect(result[0]!.day).eq("Mi");
+    expect(result[3]!.start.getHours()).eq(11);
+    expect(result[3]!.end.getHours()).eq(12);
+    expect(result[3]!.day).eq("Mi");
 
-    expect(result[1]!.startHour).eq(12);
-    expect(result[1]!.endHour).eq(13);
-    expect(result[1]!.day).eq("Mi");
+    expect(result[4]!.start.getHours()).eq(12);
+    expect(result[4]!.end.getHours()).eq(12);
+    expect(result[4]!.day).eq("Mi");
 
-    expect(result[11]!.startHour).eq(22);
-    expect(result[11]!.endHour).eq(23);
+    expect(result[11]!.start.getHours()).eq(13);
+    expect(result[11]!.end.getHours()).eq(14);
     expect(result[11]!.day).eq("Mi");
-
-    expect(result[24]!.startHour).eq(11);
-    expect(result[24]!.endHour).eq(12);
-    expect(result[24]!.day).eq("Do");
   });
 
   test("slots after target should be toLate", () => {
     expect(result[0]!.toLate).eq(false);
     expect(result[1]!.toLate).eq(false);
-    expect(result[2]!.toLate).eq(true);
-    expect(result[3]!.toLate).eq(true);
+    expect(result[10]!.toLate).eq(true);
+    expect(result[10]!.toLate).eq(true);
   });
 
   test("slots are marked if charging is happening in them", () => {
     expect(result[0]!.charging).eq(false);
-    expect(result[1]!.charging).eq(true);
-    expect(result[2]!.charging).eq(false);
-    expect(result[3]!.charging).eq(false);
+    expect(result[4]!.charging).eq(true);
+    expect(result[8]!.charging).eq(false);
   });
 
   test("all slots have the same fixed value", () => {
@@ -124,17 +119,19 @@ describe("zoned tariffs", () => {
   });
 
   test("handle multiple charging slots", () => {
-    expect(result[0]!.charging).eq(true);
-    expect(result[1]!.charging).eq(true);
-    expect(result[2]!.charging).eq(false);
-    expect(result[3]!.charging).eq(true);
+    expect(result[0]!.charging).eq(false);
     expect(result[4]!.charging).eq(true);
-    expect(result[5]!.charging).eq(false);
+    expect(result[8]!.charging).eq(false);
+    expect(result[12]!.charging).eq(false);
+    expect(result[16]!.charging).eq(true);
   });
 
-  test("first slot is cheap, others are expensive", () => {
-    const [first, ...others] = result;
+  test("first hour is cheap, others are expensive", () => {
+    const [first, second, third, fourth, ...others] = result;
     expect(first!.value).eq(0.2);
+    expect(second!.value).eq(0.2);
+    expect(third!.value).eq(0.2);
+    expect(fourth!.value).eq(0.2);
     others.forEach((slot) => expect(slot.value).eq(0.4));
   });
 });
diff --git a/assets/js/components/ChargingPlans/Preview.vue b/assets/js/components/ChargingPlans/Preview.vue
index ae9557dc8..dc7f02304 100644
--- a/assets/js/components/ChargingPlans/Preview.vue
+++ b/assets/js/components/ChargingPlans/Preview.vue
@@ -26,9 +26,10 @@
 			</div>
 		</div>
 		<TariffChart
+			class="mb-3"
 			:slots="slots"
 			:target-text="targetText"
-			:target-offset="targetHourOffset"
+			:target-offset="targetOffset"
 			@slot-hovered="slotHovered"
 		/>
 	</div>
@@ -114,16 +115,16 @@ export default defineComponent({
 		},
 		activeSlotName(): string | null {
 			if (this.activeSlot) {
-				const { day, startHour, endHour } = this.activeSlot;
-				const range = `${startHour}–${endHour}`;
+				const { day, start, end } = this.activeSlot;
+				const range = `${this.fmtTimeString(start)}–${this.fmtTimeString(end)}`;
 				return this.$t("main.targetChargePlan.timeRange", { day, range });
 			}
 			return null;
 		},
-		targetHourOffset(): number | undefined {
+		targetOffset(): number | undefined {
 			if (!this.targetTime) return;
 			const start = new Date(this.startTime);
-			start.setMinutes(0);
+			start.setMinutes(start.getMinutes() - (start.getMinutes() % 15));
 			start.setSeconds(0);
 			start.setMilliseconds(0);
 			return (this.targetTime.getTime() - start.getTime()) / (60 * 60 * 1000);
@@ -135,44 +136,36 @@ export default defineComponent({
 			return this.fmtWeekdayTime(this.targetTime);
 		},
 		slots(): Slot[] {
-			const result = [];
 			const rates = this.convertDates(this.rates);
 			const plan = this.convertDates(this.plan);
-			const oneHour = 60 * 60 * 1000;
-			for (let i = 0; i < 39; i++) {
-				const start = new Date(this.startTime.getTime() + oneHour * i);
-				const startHour = start.getHours();
-				start.setMinutes(0);
-				start.setSeconds(0);
-				start.setMilliseconds(0);
-				const end = new Date(start.getTime());
-				end.setHours(startHour + 1);
-				const endHour = end.getHours();
-				const day = this.weekdayShort(start);
-				const toLate = this.targetTime && this.targetTime <= start;
-				// TODO: handle multiple matching time slots
-				const value = this.findSlotInRange(start, end, rates)?.value;
-				const isTarget =
-					this.targetTime && start <= this.targetTime && end > this.targetTime;
-				const charging = this.findSlotInRange(start, end, plan) != null;
+			const quarterHour = 15 * 60 * 1000;
+
+			const base = new Date(this.startTime);
+			base.setSeconds(0, 0);
+			base.setMinutes(base.getMinutes() - (base.getMinutes() % 15));
+
+			return Array.from({ length: 48 * 4 }, (_, i) => {
+				const start = new Date(base.getTime() + quarterHour * i);
+				const end = new Date(start.getTime() + quarterHour);
+				const charging = !!this.findSlotInRange(start, end, plan);
 				const warning =
 					charging &&
 					this.targetTime &&
 					this.endTime &&
 					end > this.targetTime &&
 					this.targetTime < this.endTime;
-				result.push({
-					day,
-					value,
-					startHour,
-					endHour,
+
+				return {
+					day: this.weekdayShort(start),
+					value: this.findSlotInRange(start, end, rates)?.value,
+					start,
+					end,
 					charging,
-					toLate,
+					toLate: this.targetTime && this.targetTime <= start,
 					warning,
-					isTarget,
-				});
-			}
-			return result;
+					isTarget: this.targetTime && start <= this.targetTime && end > this.targetTime,
+				};
+			});
 		},
 	},
 	watch: {
diff --git a/assets/js/components/Forecast/ActiveSlot.vue b/assets/js/components/Forecast/ActiveSlot.vue
index 918f3852a..efe5d96a2 100644
--- a/assets/js/components/Forecast/ActiveSlot.vue
+++ b/assets/js/components/Forecast/ActiveSlot.vue
@@ -1,9 +1,9 @@
 <template>
-	<div v-if="isSlot" class="text-end">
+	<div v-if="isSlot" class="text-end tabular">
 		<span class="text-nowrap">{{ day }} {{ start }}</span
 		>{{ " " }}<span class="text-nowrap">– {{ end }}</span>
 	</div>
-	<div v-if="isTimeseries" class="text-end">
+	<div v-if="isTimeseries" class="text-end tabular">
 		<span class="text-nowrap">{{ time }}</span>
 	</div>
 </template>
@@ -32,15 +32,15 @@ export default defineComponent({
 		},
 		start() {
 			const startDate = new Date((this.activeSlot! as ForecastSlot).start);
-			return this.hourShort(startDate);
+			return this.fmtHourMinute(startDate);
 		},
 		end() {
 			const endDate = new Date((this.activeSlot! as ForecastSlot).end);
-			return this.hourShort(endDate);
+			return this.fmtHourMinute(endDate);
 		},
 		time() {
 			const time = new Date((this.activeSlot! as TimeseriesEntry).ts);
-			return `${this.weekdayShort(time)} ${this.hourShort(time)}`;
+			return `${this.weekdayShort(time)} ${this.fmtHourMinute(time)}`;
 		},
 	},
 });
diff --git a/assets/js/components/Forecast/Chart.vue b/assets/js/components/Forecast/Chart.vue
index 134a6f1a1..840b1f5c5 100644
--- a/assets/js/components/Forecast/Chart.vue
+++ b/assets/js/components/Forecast/Chart.vue
@@ -153,7 +153,7 @@ export default defineComponent({
 					backgroundColor: lighterColor(color),
 					borderColor: color,
 					fill: "start",
-					tension: 0.5,
+					tension: 0.05,
 					pointRadius: 0,
 					animation: {
 						y: { duration: this.animations ? 500 : 0 },
@@ -178,7 +178,7 @@ export default defineComponent({
 								: index === this.maxPriceIndex || index === this.minPriceIndex),
 					})),
 					yAxisID: "yPrice",
-					borderRadius: 8,
+					borderRadius: 2,
 					backgroundColor: color,
 					borderColor: color,
 					order: active ? 0 : 1,
@@ -206,7 +206,7 @@ export default defineComponent({
 					yAxisID: "yCo2",
 					backgroundColor: color,
 					borderColor: color,
-					tension: 0.25,
+					tension: 0.05,
 					pointRadius: 0,
 					pointHoverRadius: active ? 4 : 0,
 					spanGaps: true,
diff --git a/assets/js/components/Forecast/Details.vue b/assets/js/components/Forecast/Details.vue
index 003529ed9..276606219 100644
--- a/assets/js/components/Forecast/Details.vue
+++ b/assets/js/components/Forecast/Details.vue
@@ -67,10 +67,13 @@ import { defineComponent, type PropType } from "vue";
 import formatter, { POWER_UNIT } from "@/mixins/formatter";
 import AnimatedNumber from "../Helper/AnimatedNumber.vue";
 import type { CURRENCY, Timeout } from "@/types/evcc";
-import { ForecastType } from "@/utils/forecast";
+import { ForecastType, findLowestSumSlotIndex } from "@/utils/forecast";
 import type { ForecastSlot, SolarDetails } from "./types";
 const LOCALES_WITHOUT_DAY_AFTER_TOMORROW = ["en", "tr"];
 
+const FORECASTED_HOURS = 48;
+const SLOTS_PER_HOUR = 4;
+
 export interface Energy {
 	energy: string;
 	incomplete: boolean;
@@ -111,7 +114,9 @@ export default defineComponent({
 		upcomingSlots(): ForecastSlot[] {
 			const now = this.now;
 			const slots = this.isPrice ? this.grid || [] : this.co2 || [];
-			return slots.filter((slot) => new Date(slot.end) > now).slice(0, 48);
+			return slots
+				.filter((slot) => new Date(slot.end) > now)
+				.slice(0, FORECASTED_HOURS * SLOTS_PER_HOUR);
 		},
 		averagePrice() {
 			if (this.isSolar) return "";
@@ -129,12 +134,15 @@ export default defineComponent({
 		lowestPriceHour() {
 			if (this.isSolar) return "";
 			const slots = this.upcomingSlots;
-			const min = Math.min(...slots.map((slot) => slot.value));
-			const slot = slots.find((slot) => slot.value === min);
-			if (!slot) return "";
-			const start = new Date(slot.start);
-			const end = new Date(slot.end);
-			return `${this.weekdayShort(start)} ${this.hourShort(start)} – ${this.hourShort(end)}`;
+			const index = findLowestSumSlotIndex(slots, SLOTS_PER_HOUR);
+			if (index === -1) return "";
+			const startSlot = slots[index];
+			const endSlot = slots[index + SLOTS_PER_HOUR - 1];
+			if (!startSlot || !endSlot) return "";
+			const start = new Date(startSlot.start);
+			const end = new Date(endSlot.end);
+
+			return `${this.weekdayShort(start)} ${this.fmtHourMinute(start)} – ${this.fmtHourMinute(end)}`;
 		},
 		highlightColor() {
 			switch (this.type) {
diff --git a/assets/js/components/Loadpoints/SettingsModal.vue b/assets/js/components/Loadpoints/SettingsModal.vue
index 8c42db1a0..2c9aeea04 100644
--- a/assets/js/components/Loadpoints/SettingsModal.vue
+++ b/assets/js/components/Loadpoints/SettingsModal.vue
@@ -17,7 +17,7 @@
 				:multiple-loadpoints="multipleLoadpoints"
 				:possible="smartCostAvailable"
 				:tariff="forecast?.planner"
-				class="mt-2"
+				class="mt-2 mb-4"
 			/>
 			<SmartFeedInPriority
 				:current-limit="smartFeedInPriorityLimit"
@@ -26,7 +26,7 @@
 				:multiple-loadpoints="multipleLoadpoints"
 				:possible="smartFeedInPriorityAvailable"
 				:tariff="forecast?.feedin"
-				class="mt-2"
+				class="mt-2 mb-4"
 			/>
 			<LoadpointSettingsBatteryBoost
 				v-if="batteryBoostAvailable"
diff --git a/assets/js/components/Optimize/ChargeChart.vue b/assets/js/components/Optimize/ChargeChart.vue
index 7d59908a0..0dccc5b2a 100644
--- a/assets/js/components/Optimize/ChargeChart.vue
+++ b/assets/js/components/Optimize/ChargeChart.vue
@@ -82,8 +82,21 @@ export default defineComponent({
 		timeLabels(): string[] {
 			const startTime = new Date(this.timestamp);
 			return this.evopt.req.time_series.dt.map((_, index) => {
-				const currentTime = new Date(startTime.getTime() + index * 60 * 60 * 1000); // Add hours
-				return currentTime.getHours().toString();
+				// Calculate cumulative time from dt array
+				let cumulativeSeconds = 0;
+				for (let i = 0; i < index; i++) {
+					cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+				}
+
+				const currentTime = new Date(startTime.getTime() + cumulativeSeconds * 1000);
+				const hour = currentTime.getHours();
+				const minute = currentTime.getMinutes();
+
+				// Only show labels at exact hour boundaries divisible by 4
+				if (minute === 0 && hour % 4 === 0) {
+					return hour.toString();
+				}
+				return "";
 			});
 		},
 		chartData(): ChartData {
@@ -116,6 +129,10 @@ export default defineComponent({
 					mode: "index",
 					intersect: false,
 				},
+				hover: {
+					mode: "index",
+					intersect: false,
+				},
 				elements: {
 					point: {
 						radius: 0, // Hide points by default
@@ -133,6 +150,10 @@ export default defineComponent({
 						mode: "index",
 						intersect: false,
 						callbacks: {
+							title: (context) => {
+								const index = context[0]?.dataIndex;
+								return this.formatTimeRange(index ?? 0);
+							},
 							label: (context) => {
 								const label = context.dataset.label || "";
 								const value = context.parsed.y;
@@ -162,7 +183,43 @@ export default defineComponent({
 						},
 						stacked: true,
 						grid: {
-							display: false,
+							display: true,
+							drawOnChartArea: true,
+							drawTicks: true,
+							color: "transparent",
+							tickLength: 4,
+						},
+						ticks: {
+							autoSkip: false,
+							maxRotation: 0,
+							minRotation: 0,
+							callback: (_value, index) => {
+								const startTime = new Date(this.timestamp);
+
+								// Calculate cumulative time from dt array
+								let cumulativeSeconds = 0;
+								for (let i = 0; i < index; i++) {
+									cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+								}
+
+								const currentTime = new Date(
+									startTime.getTime() + cumulativeSeconds * 1000
+								);
+								const hour = currentTime.getHours();
+								const minute = currentTime.getMinutes();
+
+								// Show ticks at exact hour boundaries
+								if (minute === 0) {
+									// Show labels only at hours divisible by 4
+									if (hour % 4 === 0) {
+										return hour.toString();
+									}
+									// Show tick but no label for other hours
+									return "";
+								}
+								// Return undefined to skip this tick entirely
+								return undefined;
+							},
 						},
 					},
 					y: {
@@ -325,6 +382,28 @@ export default defineComponent({
 			const detail = this.batteryDetails[index];
 			return detail ? detail.title || detail.name : `Battery ${index + 1}`;
 		},
+
+		formatTimeRange(index: number): string {
+			const startTime = new Date(this.timestamp);
+
+			// Calculate cumulative time from dt array
+			let cumulativeSeconds = 0;
+			for (let i = 0; i < index; i++) {
+				cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+			}
+
+			const slotStart = new Date(startTime.getTime() + cumulativeSeconds * 1000);
+			const slotDuration = this.evopt.req.time_series.dt[index] || 0;
+			const slotEnd = new Date(slotStart.getTime() + slotDuration * 1000);
+
+			const formatTime = (date: Date): string => {
+				const hours = date.getHours().toString().padStart(2, "0");
+				const minutes = date.getMinutes().toString().padStart(2, "0");
+				return `${hours}:${minutes}`;
+			};
+
+			return `${formatTime(slotStart)} - ${formatTime(slotEnd)}`;
+		},
 	},
 });
 </script>
diff --git a/assets/js/components/Optimize/PriceChart.vue b/assets/js/components/Optimize/PriceChart.vue
index c1a14d890..c3599e565 100644
--- a/assets/js/components/Optimize/PriceChart.vue
+++ b/assets/js/components/Optimize/PriceChart.vue
@@ -72,8 +72,21 @@ export default defineComponent({
 		timeLabels(): string[] {
 			const startTime = new Date(this.timestamp);
 			return this.evopt.req.time_series.dt.map((_, index) => {
-				const currentTime = new Date(startTime.getTime() + index * 60 * 60 * 1000); // Add hours
-				return currentTime.getHours().toString();
+				// Calculate cumulative time from dt array
+				let cumulativeSeconds = 0;
+				for (let i = 0; i < index; i++) {
+					cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+				}
+
+				const currentTime = new Date(startTime.getTime() + cumulativeSeconds * 1000);
+				const hour = currentTime.getHours();
+				const minute = currentTime.getMinutes();
+
+				// Only show labels at exact hour boundaries divisible by 4
+				if (minute === 0 && hour % 4 === 0) {
+					return hour.toString();
+				}
+				return "";
 			});
 		},
 		chartData(): ChartData {
@@ -114,6 +127,10 @@ export default defineComponent({
 						mode: "index",
 						intersect: false,
 						callbacks: {
+							title: (context) => {
+								const index = context[0]?.dataIndex;
+								return this.formatTimeRange(index ?? 0);
+							},
 							label: (context) => {
 								const label = context.dataset.label || "";
 								const value = context.parsed.y;
@@ -132,7 +149,43 @@ export default defineComponent({
 							display: false,
 						},
 						grid: {
-							display: false,
+							display: true,
+							drawOnChartArea: true,
+							drawTicks: true,
+							color: "transparent",
+							tickLength: 4,
+						},
+						ticks: {
+							autoSkip: false,
+							maxRotation: 0,
+							minRotation: 0,
+							callback: (_value, index) => {
+								const startTime = new Date(this.timestamp);
+
+								// Calculate cumulative time from dt array
+								let cumulativeSeconds = 0;
+								for (let i = 0; i < index; i++) {
+									cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+								}
+
+								const currentTime = new Date(
+									startTime.getTime() + cumulativeSeconds * 1000
+								);
+								const hour = currentTime.getHours();
+								const minute = currentTime.getMinutes();
+
+								// Show ticks at exact hour boundaries
+								if (minute === 0) {
+									// Show labels only at hours divisible by 4
+									if (hour % 4 === 0) {
+										return hour.toString();
+									}
+									// Show tick but no label for other hours
+									return "";
+								}
+								// Return undefined to skip this tick entirely
+								return undefined;
+							},
 						},
 					},
 					y: {
@@ -218,6 +271,28 @@ export default defineComponent({
 			const unit = this.pricePerKWhUnit(this.currency, false);
 			return `${formattedValue} ${unit}`;
 		},
+
+		formatTimeRange(index: number): string {
+			const startTime = new Date(this.timestamp);
+
+			// Calculate cumulative time from dt array
+			let cumulativeSeconds = 0;
+			for (let i = 0; i < index; i++) {
+				cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+			}
+
+			const slotStart = new Date(startTime.getTime() + cumulativeSeconds * 1000);
+			const slotDuration = this.evopt.req.time_series.dt[index] || 0;
+			const slotEnd = new Date(slotStart.getTime() + slotDuration * 1000);
+
+			const formatTime = (date: Date): string => {
+				const hours = date.getHours().toString().padStart(2, "0");
+				const minutes = date.getMinutes().toString().padStart(2, "0");
+				return `${hours}:${minutes}`;
+			};
+
+			return `${formatTime(slotStart)} - ${formatTime(slotEnd)}`;
+		},
 	},
 });
 </script>
diff --git a/assets/js/components/Optimize/SocChart.vue b/assets/js/components/Optimize/SocChart.vue
index 0b12148cb..72c7b4ab9 100644
--- a/assets/js/components/Optimize/SocChart.vue
+++ b/assets/js/components/Optimize/SocChart.vue
@@ -1,15 +1,25 @@
 <template>
 	<div class="mb-5">
-		<div class="chart-container my-3">
-			<Chart
-				ref="chartRef"
-				type="bar"
-				:data="chartData"
-				:options="chartOptions"
-				:height="150"
-			/>
+		<div v-for="(_battery, index) in evopt.res.batteries" :key="index" class="mb-3">
+			<div class="mb-2" style="font-size: 0.875rem; font-weight: bold">
+				{{ getBatteryTitle(index) }}
+			</div>
+			<div
+				:class="
+					index === evopt.res.batteries.length - 1
+						? 'chart-container-small-with-labels'
+						: 'chart-container-small'
+				"
+			>
+				<Chart
+					:ref="`chartRef${index}`"
+					type="bar"
+					:data="getBatteryChartData(index)"
+					:options="getBatteryChartOptions(index)"
+					:height="75"
+				/>
+			</div>
 		</div>
-		<LegendList :legends="legends" />
 	</div>
 </template>
 
@@ -31,8 +41,6 @@ import type { EvoptData } from "./TimeSeriesDataTable.vue";
 import type { CURRENCY, BatteryDetail } from "@/types/evcc";
 import formatter from "@/mixins/formatter";
 import colors from "@/colors";
-import LegendList from "../Sessions/LegendList.vue";
-import type { Legend } from "../Sessions/types";
 
 ChartJS.register(CategoryScale, LinearScale, BarElement, Title, Tooltip, ChartLegendPlugin);
 
@@ -40,7 +48,6 @@ export default defineComponent({
 	name: "SocChart",
 	components: {
 		Chart,
-		LegendList,
 	},
 	mixins: [formatter],
 	props: {
@@ -65,26 +72,54 @@ export default defineComponent({
 			default: () => [],
 		},
 	},
-	computed: {
-		timeLabels(): string[] {
+	computed: {},
+	methods: {
+		getTimeLabels(): string[] {
 			const startTime = new Date(this.timestamp);
 			return this.evopt.req.time_series.dt.map((_, index) => {
-				const currentTime = new Date(startTime.getTime() + index * 60 * 60 * 1000); // Add hours
-				return currentTime.getHours().toString();
+				// Calculate cumulative time from dt array
+				let cumulativeSeconds = 0;
+				for (let i = 0; i < index; i++) {
+					cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+				}
+
+				const currentTime = new Date(startTime.getTime() + cumulativeSeconds * 1000);
+				const hour = currentTime.getHours();
+				const minute = currentTime.getMinutes();
+
+				// Only show labels at exact hour boundaries divisible by 4
+				if (minute === 0 && hour % 4 === 0) {
+					return hour.toString();
+				}
+				return "";
 			});
 		},
-		chartData(): ChartData {
-			const datasets: any[] = [];
 
-			// 1. Battery SoC data
-			datasets.push(...this.getBatterySocDatasets());
+		getBatteryChartData(batteryIndex: number): ChartData {
+			const battery = this.evopt.res.batteries[batteryIndex];
+			if (!battery) {
+				return { labels: [], datasets: [] };
+			}
+			const baseColor = this.batteryColors[batteryIndex] || "";
 
 			return {
-				labels: this.timeLabels,
-				datasets: datasets,
+				labels: this.getTimeLabels(),
+				datasets: [
+					{
+						label: this.getBatteryTitle(batteryIndex),
+						data: battery.state_of_charge.map((socWh) =>
+							this.convertWhToPercentage(socWh, batteryIndex)
+						),
+						backgroundColor: baseColor,
+						borderWidth: 0,
+						yAxisID: "y",
+					},
+				],
 			};
 		},
-		chartOptions(): ChartOptions {
+
+		getBatteryChartOptions(batteryIndex: number): ChartOptions {
+			const isLastBattery = batteryIndex === this.evopt.res.batteries.length - 1;
 			return {
 				responsive: true,
 				maintainAspectRatio: false,
@@ -105,11 +140,13 @@ export default defineComponent({
 						mode: "index",
 						intersect: false,
 						callbacks: {
+							title: (context) => {
+								const index = context[0]?.dataIndex;
+								return this.formatTimeRange(index ?? 0);
+							},
 							label: (context) => {
-								const label = context.dataset.label || "";
 								const value = context.parsed.y;
-								// Percentage axis (%)
-								return `${label}: ${this.formatValue(value)}%`;
+								return `SoC: ${this.formatValue(value)}%`;
 							},
 						},
 					},
@@ -123,64 +160,66 @@ export default defineComponent({
 							display: false,
 						},
 						grid: {
-							display: false,
+							display: true,
+							drawOnChartArea: true,
+							drawTicks: true,
+							color: "transparent",
+							tickLength: 4,
+						},
+						ticks: {
+							display: isLastBattery,
+							autoSkip: false,
+							maxRotation: 0,
+							minRotation: 0,
+							callback: (_value, index) => {
+								const startTime = new Date(this.timestamp);
+
+								// Calculate cumulative time from dt array
+								let cumulativeSeconds = 0;
+								for (let i = 0; i < index; i++) {
+									cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+								}
+
+								const currentTime = new Date(
+									startTime.getTime() + cumulativeSeconds * 1000
+								);
+								const hour = currentTime.getHours();
+								const minute = currentTime.getMinutes();
+
+								// Show ticks at exact hour boundaries
+								if (minute === 0) {
+									// Show labels only at hours divisible by 4
+									if (hour % 4 === 0) {
+										return hour.toString();
+									}
+									// Show tick but no label for other hours
+									return "";
+								}
+								// Return undefined to skip this tick entirely
+								return undefined;
+							},
 						},
 					},
 					y: {
 						type: "linear",
 						position: "left",
+						min: 0,
+						max: 100,
 						title: {
-							display: true,
-							text: "SoC (%)",
+							display: false,
 						},
 						grid: {
 							drawOnChartArea: true,
 							color: colors.border || "",
 							lineWidth: 1,
 						},
+						ticks: {
+							callback: (value) => `${value}%`,
+						},
 					},
 				},
 			};
 		},
-		legends(): Legend[] {
-			return this.chartData.datasets
-				.filter((dataset) => !dataset.hidden)
-				.map((dataset) => {
-					const label = dataset.label || "";
-					return {
-						label,
-						color: (dataset.backgroundColor || dataset.borderColor) as string,
-						value: "", // Required by Legend type, but not used in this context
-						type: "area",
-					};
-				});
-		},
-	},
-	methods: {
-		getBatterySocDatasets() {
-			const datasets: any[] = [];
-
-			if (this.evopt.res.batteries?.length > 0) {
-				this.evopt.res.batteries.forEach((battery, index) => {
-					// Use passed battery colors
-					const baseColor = this.batteryColors[index];
-
-					// SoC as bars (full color)
-					datasets.push({
-						label: this.getBatteryTitle(index),
-						data: battery.state_of_charge.map((socWh) =>
-							this.convertWhToPercentage(socWh, index)
-						),
-						backgroundColor: baseColor,
-						borderWidth: 0,
-						yAxisID: "y",
-						type: "bar" as const,
-					});
-				});
-			}
-
-			return datasets;
-		},
 		convertWhToPercentage(wh: number, batteryIndex: number): number {
 			const detail = this.batteryDetails[batteryIndex];
 			if (detail?.capacity && detail.capacity > 0) {
@@ -195,14 +234,49 @@ export default defineComponent({
 			const detail = this.batteryDetails[index];
 			return detail ? detail.title || detail.name : `Battery ${index + 1}`;
 		},
+
+		formatTimeRange(index: number): string {
+			const startTime = new Date(this.timestamp);
+
+			// Calculate cumulative time from dt array
+			let cumulativeSeconds = 0;
+			for (let i = 0; i < index; i++) {
+				cumulativeSeconds += this.evopt.req.time_series.dt[i] || 0;
+			}
+
+			const slotStart = new Date(startTime.getTime() + cumulativeSeconds * 1000);
+			const slotDuration = this.evopt.req.time_series.dt[index] || 0;
+			const slotEnd = new Date(slotStart.getTime() + slotDuration * 1000);
+
+			const formatTime = (date: Date): string => {
+				const hours = date.getHours().toString().padStart(2, "0");
+				const minutes = date.getMinutes().toString().padStart(2, "0");
+				return `${hours}:${minutes}`;
+			};
+
+			return `${formatTime(slotStart)} - ${formatTime(slotEnd)}`;
+		},
 	},
 });
 </script>
 
 <style scoped>
-.chart-container {
+.chart-container-small {
 	position: relative;
-	height: 150px;
+	height: 75px;
 	width: 100%;
 }
+
+.chart-container-small-with-labels {
+	position: relative;
+	height: 95px;
+	width: 100%;
+}
+
+.battery-indicator {
+	width: 1rem;
+	height: 1rem;
+	border-radius: 50%;
+	flex-shrink: 0;
+}
 </style>
diff --git a/assets/js/components/Optimize/TimeSeriesDataTable.vue b/assets/js/components/Optimize/TimeSeriesDataTable.vue
index 70ca8a08b..796c96a97 100644
--- a/assets/js/components/Optimize/TimeSeriesDataTable.vue
+++ b/assets/js/components/Optimize/TimeSeriesDataTable.vue
@@ -18,7 +18,9 @@
 				<tbody>
 					<!-- Request Data -->
 					<tr class="table-secondary">
-						<td colspan="100%" class="fw-bold text-start">Request Data</td>
+						<td :colspan="timeSlots.length + 1" class="fw-bold text-start">
+							Request Data
+						</td>
 					</tr>
 					<tr>
 						<td class="fw-medium text-nowrap text-start">Solar Forecast (kW)</td>
@@ -77,7 +79,9 @@
 
 					<!-- Response Data -->
 					<tr class="table-secondary">
-						<td colspan="100%" class="fw-bold text-start">Response Data</td>
+						<td :colspan="timeSlots.length + 1" class="fw-bold text-start">
+							Response Data
+						</td>
 					</tr>
 					<tr>
 						<td class="fw-medium text-nowrap text-start">Grid Export (kW)</td>
@@ -118,7 +122,7 @@
 						:key="batteryIndex"
 					>
 						<tr>
-							<td colspan="100%" class="fw-bold text-start">
+							<td :colspan="timeSlots.length + 1" class="fw-bold text-start">
 								<div class="d-flex align-items-center">
 									<span
 										class="battery-indicator me-2"
@@ -255,11 +259,15 @@ export default defineComponent({
 			return this.fmtWh(wh, this.POWER_UNIT.KW, false, 1);
 		},
 		formatDuration: (seconds: number): string => {
-			return (seconds / 3600).toFixed(1);
+			return (seconds / 3600).toFixed(2);
 		},
 		formatHour(index: number): string {
+			// Show label only every 4th slot (every hour for 15-minute slots)
+			if (index % 4 !== 0) {
+				return "";
+			}
 			const startTime = new Date(this.timestamp);
-			const currentTime = new Date(startTime.getTime() + index * 60 * 60 * 1000); // Add hours
+			const currentTime = new Date(startTime.getTime() + index * 15 * 60 * 1000); // Add 15-minute intervals
 			return currentTime.getHours().toString();
 		},
 		getBatteryTitle(index: number): string {
diff --git a/assets/js/components/Site/Site.vue b/assets/js/components/Site/Site.vue
index 7136ba648..5fc21abf3 100644
--- a/assets/js/components/Site/Site.vue
+++ b/assets/js/components/Site/Site.vue
@@ -165,7 +165,7 @@ export default defineComponent({
 	},
 	computed: {
 		loadpoints() {
-			return store.uiLoadpoints.value;
+			return store.uiLoadpoints.value || [];
 		},
 		orderedVisibleLoadpoints() {
 			return this.loadpoints.filter((lp) => lp.visible);
diff --git a/assets/js/components/Tariff/SmartTariffBase.vue b/assets/js/components/Tariff/SmartTariffBase.vue
index cd0ca2671..6584ab521 100644
--- a/assets/js/components/Tariff/SmartTariffBase.vue
+++ b/assets/js/components/Tariff/SmartTariffBase.vue
@@ -191,21 +191,16 @@ export default defineComponent({
 				return [];
 			}
 
-			const result = [] as Slot[];
 			const rates = this.rates;
-			const startTime = new Date();
-			const oneHour = 3600000;
+			const quarterHour = 15 * 60 * 1000;
 
-			for (let i = 0; i < 42; i++) {
-				const start = new Date(startTime.getTime() + oneHour * i);
-				const startHour = start.getHours();
-				start.setMinutes(0);
-				start.setSeconds(0);
-				start.setMilliseconds(0);
-				const end = new Date(start.getTime());
-				end.setHours(startHour + 1);
-				const endHour = end.getHours();
-				const day = this.weekdayShort(start);
+			const base = new Date();
+			base.setSeconds(0, 0);
+			base.setMinutes(base.getMinutes() - (base.getMinutes() % 15));
+
+			return Array.from({ length: 48 * 4 }, (_, i) => {
+				const start = new Date(base.getTime() + quarterHour * i);
+				const end = new Date(start.getTime() + quarterHour);
 				const value = this.findRateInRange(start, end, rates)?.value;
 				const active =
 					this.limitDirection === "below" &&
@@ -217,19 +212,17 @@ export default defineComponent({
 					this.selectedLimit !== null &&
 					value !== undefined &&
 					value >= this.selectedLimit;
-				const selectable = value !== undefined;
-				result.push({
-					day,
-					value,
-					startHour,
-					endHour,
-					charging: active,
-					selectable,
-					warning,
-				});
-			}
 
-			return result;
+				return {
+					day: this.weekdayShort(start),
+					value,
+					start,
+					end,
+					charging: active,
+					selectable: value !== undefined,
+					warning,
+				};
+			});
 		},
 		totalSlots() {
 			return this.slots.filter((s) => s.value !== undefined);
@@ -258,8 +251,8 @@ export default defineComponent({
 		},
 		activeSlotName() {
 			if (this.activeSlot) {
-				const { day, startHour, endHour } = this.activeSlot;
-				const range = `${startHour}–${endHour}`;
+				const { day, start, end } = this.activeSlot;
+				const range = `${this.fmtTimeString(start)}–${this.fmtTimeString(end)}`;
 				return this.$t("main.targetChargePlan.timeRange", { day, range });
 			}
 			return null;
@@ -271,14 +264,11 @@ export default defineComponent({
 			return this.warningSlots.length ? "text-warning" : "value-inactive";
 		},
 		activeHoursText() {
-			const params = {
-				active:
-					this.limitDirection === "below"
-						? this.activeSlots.length
-						: this.warningSlots.length,
-				total: this.totalSlots.length,
-			};
-			return this.$t("smartCost.activeHours", params);
+			const active =
+				this.limitDirection === "below"
+					? this.activeSlots.length
+					: this.warningSlots.length;
+			return this.fmtDurationLong(active * 15 * 60, "short");
 		},
 		limitOperator() {
 			return this.limitDirection === "below" ? "≤" : "≥";
diff --git a/assets/js/components/Tariff/TariffChart.vue b/assets/js/components/Tariff/TariffChart.vue
index 8bf23b748..0e3d3f446 100644
--- a/assets/js/components/Tariff/TariffChart.vue
+++ b/assets/js/components/Tariff/TariffChart.vue
@@ -1,9 +1,9 @@
 <template>
 	<div class="root position-relative">
-		<div class="chart position-relative">
+		<div class="chart position-relative" :class="{ 'chart--with-target': targetText }">
 			<div
 				v-for="(slot, index) in slots"
-				:key="`${slot.day}-${slot.startHour}`"
+				:key="`${slot.day}-${fmtHourMinute(slot.start)}`"
 				:data-index="index"
 				class="slot user-select-none"
 				:class="{
@@ -22,12 +22,14 @@
 				@mouseup="hoverSlot(null)"
 				@click="selectSlot(index)"
 			>
-				<div class="slot-bar" :style="valueStyle(slot.value)">
-					<span v-if="slot.value === undefined && avgValue" class="unknown">?</span>
-				</div>
+				<div
+					class="slot-bar"
+					:style="valueStyle(slot.value)"
+					:class="{ unknown: slot.value === undefined && avgValue }"
+				></div>
 				<div class="slot-label">
-					<span v-if="!slot.isTarget || targetNearlyOutOfRange">{{
-						formatHour(slot.startHour)
+					<span v-if="slot.start.getMinutes() === 0">{{
+						formatHour(slot.start.getHours())
 					}}</span>
 					<br />
 					<span v-if="showWeekday(index)">{{ slot.day }}</span>
@@ -59,8 +61,7 @@ import { is12hFormat } from "@/units";
 import PlanEndIcon from "../MaterialIcon/PlanEnd.vue";
 import formatter from "@/mixins/formatter";
 import type { Slot } from "@/types/evcc";
-
-const BAR_WIDTH = 20;
+const BAR_WIDTH = 8;
 
 export default defineComponent({
 	name: "TariffChart",
@@ -96,12 +97,10 @@ export default defineComponent({
 			return { min, range: max - min };
 		},
 		targetLeft() {
-			const fullHours = Math.floor(this.targetOffset);
-			const hourFraction = this.targetOffset - fullHours;
-			return `${fullHours * BAR_WIDTH + 4 + hourFraction * 12}px`;
+			return `${(this.targetOffset / 0.25) * BAR_WIDTH}px`;
 		},
 		targetNearlyOutOfRange() {
-			return this.targetOffset > this.slots.length - 4;
+			return this.targetOffset > this.slots.length - 8;
 		},
 		targetOutOfRange() {
 			return this.targetOffset > this.slots.length;
@@ -142,7 +141,7 @@ export default defineComponent({
 					return false;
 				}
 			}
-			if (slot.startHour === 0) {
+			if (slot.start.getHours() === 0 && slot.start.getMinutes() === 0) {
 				return true;
 			}
 			return false;
@@ -152,7 +151,7 @@ export default defineComponent({
 			const height =
 				value !== undefined && !isNaN(val)
 					? `${10 + (90 / this.valueInfo.range) * (val - this.valueInfo.min)}%`
-					: "75%";
+					: "50%";
 			return { height };
 		},
 		startLongPress(index: number) {
@@ -179,7 +178,10 @@ export default defineComponent({
 	overflow-x: auto;
 	align-items: flex-end;
 	overflow-y: none;
-	padding-bottom: 55px;
+	padding-bottom: 35px;
+}
+.chart--with-target {
+	padding-bottom: 57px;
 }
 .target-inline {
 	height: 130px;
@@ -219,7 +221,7 @@ export default defineComponent({
 }
 .slot {
 	text-align: center;
-	padding: 4px;
+	padding: 2px;
 	height: 100%;
 	display: flex;
 	justify-content: flex-end;
@@ -229,24 +231,14 @@ export default defineComponent({
 	transition-property: opacity, background, color;
 	transition-duration: var(--evcc-transition-fast);
 	transition-timing-function: ease-in;
-	width: 20px;
+	width: 8px;
 	flex-grow: 0;
 	flex-shrink: 0;
 }
-@media (max-width: 991px) {
-	.chart {
-		overflow-x: auto;
-	}
-}
-@media (min-width: 992px) {
-	.chart {
-		overflow-x: hidden;
-	}
-}
 .slot-bar {
 	background-clip: content-box !important;
 	background: var(--bs-gray-light);
-	border-radius: 8px;
+	border-radius: 2px;
 	width: 100%;
 	align-items: center;
 	display: flex;
@@ -254,12 +246,15 @@ export default defineComponent({
 	color: var(--bs-white);
 	transition: height var(--evcc-transition-fast) ease-in;
 }
+.slot-bar.unknown {
+	opacity: 0.33;
+}
 .slot-label {
 	color: var(--bs-gray-light);
 	line-height: 1.1;
 	position: absolute;
 	top: 100%;
-	left: -50%;
+	left: -100%;
 	width: 200%;
 	text-align: center;
 }
@@ -281,9 +276,6 @@ export default defineComponent({
 .slot.warning .slot-label {
 	color: var(--bs-warning);
 }
-.unknown {
-	margin: 0 -0.5rem;
-}
 .slot.hovered {
 	opacity: 1;
 }
diff --git a/assets/js/mixins/formatter.ts b/assets/js/mixins/formatter.ts
index 68dec9af9..0ff3224ba 100644
--- a/assets/js/mixins/formatter.ts
+++ b/assets/js/mixins/formatter.ts
@@ -157,7 +157,7 @@ export default defineComponent({
       }
       return result;
     },
-    fmtDurationLong(seconds: number) {
+    fmtDurationLong(seconds: number, style: "short" | "long" = "long") {
       // @ts-expect-error - Intl.DurationFormat is a new API not yet in TS types, see https://github.com/microsoft/TypeScript/issues/60608
       if (!Intl.DurationFormat) {
         // old browser fallback
@@ -167,7 +167,7 @@ export default defineComponent({
       const minutes = Math.floor((seconds % 3600) / 60);
 
       // @ts-expect-error - Intl.DurationFormat is a new API not yet in TS types, see https://github.com/microsoft/TypeScript/issues/60608
-      const formatter = new Intl.DurationFormat(this.$i18n?.locale, { style: "long" });
+      const formatter = new Intl.DurationFormat(this.$i18n?.locale, { style });
       return formatter.format({ minutes, hours });
     },
     fmtDayString(date: Date) {
diff --git a/assets/js/types/evcc.ts b/assets/js/types/evcc.ts
index 6f9aa75ae..9244ee45d 100644
--- a/assets/js/types/evcc.ts
+++ b/assets/js/types/evcc.ts
@@ -391,8 +391,8 @@ export interface Rate {
 export interface Slot {
   day: string;
   value?: number;
-  startHour: number;
-  endHour: number;
+  start: Date;
+  end: Date;
   charging: boolean;
   toLate?: boolean | null;
   warning?: boolean | null;
@@ -437,7 +437,6 @@ export type ValueOf<T> = T[keyof T];
 export interface EvOpt {
   req: OptimizationInput;
   res: OptimizationResult;
-  curl: string;
   details: OptimizationDetails;
 }
 
diff --git a/assets/js/utils/forecast.test.ts b/assets/js/utils/forecast.test.ts
new file mode 100644
index 000000000..7a1ba0265
--- /dev/null
+++ b/assets/js/utils/forecast.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, test } from "vitest";
+import { findLowestSumSlotIndex } from "./forecast";
+
+describe("findLowestSumSlotIndex", () => {
+  test("finds lowest sum with span of 4", () => {
+    const slots = [
+      { start: "2025-01-01T00:00:00Z", value: 10 },
+      { start: "2025-01-01T00:15:00Z", value: 8 },
+      { start: "2025-01-01T00:30:00Z", value: 6 },
+      { start: "2025-01-01T00:45:00Z", value: 4 }, // sum 28 (index 0)
+      { start: "2025-01-01T01:00:00Z", value: 2 }, // sum 20 (index 1)
+      { start: "2025-01-01T01:15:00Z", value: 3 }, // sum 14 (index 2)
+      { start: "2025-01-01T01:30:00Z", value: 5 }, // sum 13 (index 3) lowest
+      { start: "2025-01-01T01:45:00Z", value: 7 }, // sum 17 (index 4)
+    ];
+    expect(findLowestSumSlotIndex(slots, 4)).toBe(3);
+  });
+
+  test("returns -1 when not enough slots", () => {
+    const slots = [
+      { start: "2025-01-01T00:00:00Z", value: 10 },
+      { start: "2025-01-01T00:15:00Z", value: 8 },
+    ];
+    expect(findLowestSumSlotIndex(slots, 4)).toBe(-1);
+  });
+
+  test("handles exact span length", () => {
+    const slots = [
+      { start: "2025-01-01T00:00:00Z", value: 5 },
+      { start: "2025-01-01T00:15:00Z", value: 3 },
+      { start: "2025-01-01T00:30:00Z", value: 2 },
+      { start: "2025-01-01T00:45:00Z", value: 1 },
+    ];
+    expect(findLowestSumSlotIndex(slots, 4)).toBe(0);
+  });
+
+  test("finds lowest at end", () => {
+    const slots = [
+      { start: "2025-01-01T00:00:00Z", value: 10 },
+      { start: "2025-01-01T00:15:00Z", value: 10 },
+      { start: "2025-01-01T00:30:00Z", value: 1 },
+      { start: "2025-01-01T00:45:00Z", value: 1 },
+      { start: "2025-01-01T01:00:00Z", value: 1 },
+    ];
+    expect(findLowestSumSlotIndex(slots, 3)).toBe(2);
+  });
+
+  test("returns first index when multiple equal sums", () => {
+    const slots = [
+      { start: "2025-01-01T00:00:00Z", value: 2 },
+      { start: "2025-01-01T00:15:00Z", value: 2 }, // sum 4
+      { start: "2025-01-01T00:30:00Z", value: 2 }, // sum 4 (same)
+      { start: "2025-01-01T00:45:00Z", value: 2 },
+    ];
+    expect(findLowestSumSlotIndex(slots, 2)).toBe(0);
+  });
+});
diff --git a/assets/js/utils/forecast.ts b/assets/js/utils/forecast.ts
index de6815483..66314158e 100644
--- a/assets/js/utils/forecast.ts
+++ b/assets/js/utils/forecast.ts
@@ -64,3 +64,26 @@ export function adjustedSolar(solar?: SolarDetails): SolarDetails | undefined {
 
   return result;
 }
+
+export interface SlotWithValue {
+  start: string | Date;
+  value: number;
+}
+
+// find index of first slot with lowest sum over span (e.g. span=4 for 1h with 15min slots)
+export function findLowestSumSlotIndex(slots: SlotWithValue[], span: number): number {
+  if (slots.length < span) return -1;
+
+  let lowestSum = Infinity;
+  let lowestIndex = -1;
+
+  for (let i = 0; i <= slots.length - span; i++) {
+    const sum = slots.slice(i, i + span).reduce((acc, slot) => acc + slot.value, 0);
+    if (sum < lowestSum) {
+      lowestSum = sum;
+      lowestIndex = i;
+    }
+  }
+
+  return lowestIndex;
+}
diff --git a/assets/js/views/Optimize.vue b/assets/js/views/Optimize.vue
index cdfbdd8a8..eb242c371 100644
--- a/assets/js/views/Optimize.vue
+++ b/assets/js/views/Optimize.vue
@@ -83,19 +83,6 @@
 
 						<h3 class="fw-normal mb-4">Raw Data</h3>
 
-						<div class="mb-4">
-							<p class="mb-2">Curl Command:</p>
-							<div class="position-relative">
-								<div
-									class="p-3 rounded border overflow-auto"
-									style="background-color: var(--evcc-box)"
-								>
-									<code class="text-nowrap d-block">{{ evopt.curl }}</code>
-								</div>
-								<CopyButton :content="evopt.curl" />
-							</div>
-						</div>
-
 						<div class="mb-4">
 							<p class="mb-2">Request:</p>
 							<div class="position-relative">
diff --git a/cmd/demo.yaml b/cmd/demo.yaml
index 029d0cafb..5567aa802 100644
--- a/cmd/demo.yaml
+++ b/cmd/demo.yaml
@@ -256,9 +256,9 @@ tariffs:
   currency: EUR # three letter ISO-4217 currency code (default EUR)
   grid:
     type: template
-    template: energy-charts-api # epex spot market prices
-    bzn: DE-LU
-    charges: 0.15
+    template: demo-dynamic-grid
+    min: 0.18
+    max: 0.41
   feedin:
     type: fixed
     price: 0.08 # EUR/kWh
diff --git a/core/site_optimizer.go b/core/site_optimizer.go
index f1efb55cf..19b58b5c0 100644
--- a/core/site_optimizer.go
+++ b/core/site_optimizer.go
@@ -12,12 +12,12 @@ import (
 	"github.com/evcc-io/evcc/api"
 	"github.com/evcc-io/evcc/core/loadpoint"
 	"github.com/evcc-io/evcc/core/metrics"
+	"github.com/evcc-io/evcc/tariff"
 	"github.com/evcc-io/evcc/util/config"
 	"github.com/evcc-io/evcc/util/request"
 	"github.com/evcc-io/evcc/util/sponsor"
 	"github.com/jinzhu/now"
 	"github.com/samber/lo"
-	"moul.io/http2curl"
 )
 
 var (
@@ -94,7 +94,10 @@ func (site *Site) optimizerUpdate(battery []measurement) error {
 		firstSlotDuration,
 	)
 
-	gt := site.homeProfile(minLen)
+	gt, err := site.homeProfile(minLen, firstSlotDuration)
+	if err != nil {
+		return err
+	}
 
 	solarEnergy, err := ratesToEnergy(solar, firstSlotDuration)
 	if err != nil {
@@ -267,12 +270,10 @@ func (site *Site) optimizerUpdate(battery []measurement) error {
 		return err
 	}
 
-	var curl *http2curl.CurlCommand
 	resp, err := apiClient.PostOptimizeChargeScheduleWithResponse(context.TODO(), req, func(_ context.Context, req *http.Request) error {
 		if sponsor.IsAuthorized() {
 			req.Header.Set("Authorization", "Bearer "+sponsor.Token)
 		}
-		curl, _ = http2curl.GetCurlCommand(req)
 		return nil
 	})
 	if err != nil {
@@ -294,12 +295,10 @@ func (site *Site) optimizerUpdate(battery []measurement) error {
 	site.publish("evopt", struct {
 		Req     evopt.OptimizationInput  `json:"req"`
 		Res     evopt.OptimizationResult `json:"res"`
-		Curl    string                   `json:"curl"`
 		Details responseDetails          `json:"details"`
 	}{
 		Req:     req,
 		Res:     *resp.JSON200,
-		Curl:    curl.String(),
 		Details: details,
 	})
 
@@ -360,27 +359,22 @@ func loadpointProfile(lp loadpoint.API, firstSlotDuration time.Duration, minLen
 }
 
 // homeProfile returns the home base load in Wh
-func (site *Site) homeProfile(minLen int) []float64 {
+func (site *Site) homeProfile(minLen int, firstSlotDuration time.Duration) ([]float64, error) {
 	// kWh over last 30 days
 	profile, err := metrics.Profile(now.BeginningOfDay().AddDate(0, 0, -30))
 	if err != nil {
-		site.log.WARN.Println("optimizer:", err)
-		return lo.RepeatBy(minLen, func(_ int) float64 {
-			return 0
-		})
+		return nil, err
 	}
 
 	// max 4 days
-	hours := make([]float64, 0, minLen+1)
-
-	combined := combineSlots(profile[:])
-	for len(hours) <= minLen+24 { // allow for prorating first day
-		hours = append(hours, combined...)
+	slots := make([]float64, 0, minLen+1)
+	for len(slots) <= minLen+24*4 { // allow for prorating first day
+		slots = append(slots, profile[:]...)
 	}
 
-	res := prorateFirstHour(time.Now(), hours)
+	res := prorateFirstSlot(slots, firstSlotDuration)
 	if len(res) < minLen {
-		panic("minimum home profile length failed")
+		return nil, fmt.Errorf("minimum home profile length %d is less than required %d", len(res), minLen)
 	}
 	if len(res) > minLen {
 		res = res[:minLen]
@@ -389,41 +383,17 @@ func (site *Site) homeProfile(minLen int) []float64 {
 	// convert to Wh
 	return lo.Map(res, func(v float64, i int) float64 {
 		return v * 1e3
-	})
+	}), nil
 }
 
-// combineSlots combines 15-minute slots into hourly values
-func combineSlots(profile []float64) []float64 {
-	if profile == nil {
-		return []float64{}
-	}
+// prorateFirstSlot strips away any slots before "now" and prorates the first slot based on remaining time in current slot.
+// The profile contains 48 15min slots (00:00-23:45) that repeat for multiple days.
+func prorateFirstSlot(profile []float64, firstSlotDuration time.Duration) []float64 {
+	firstSlot := int(time.Now().Truncate(tariff.SlotDuration).Sub(now.BeginningOfDay()) / tariff.SlotDuration)
 
-	result := make([]float64, 0, 24)
-
-	// Process complete hours starting from the start slot
-	for hour := range 24 {
-		var sum float64
-		for i := range 4 {
-			sum += profile[4*hour+i]
-		}
-
-		result = append(result, sum)
-	}
-
-	return result
-}
-
-// prorateFirstHour strips away any slots before "now" and prorates the first remaining hour
-// based on remaining time in current hour. The profile contains hourly slots (0-23) that repeat for multiple days.
-func prorateFirstHour(now time.Time, profile []float64) []float64 {
 	// Take only slots from current hour onwards
-	res := profile[now.Hour():]
-
-	// Prorate the first hour based on remaining time in current hour
-	if minutesIntoHour := now.Minute(); minutesIntoHour > 0 {
-		fractionOfHour := float64(60-minutesIntoHour) / 60.0
-		res[0] *= fractionOfHour
-	}
+	res := profile[firstSlot:]
+	res[0] *= float64(firstSlotDuration / tariff.SlotDuration)
 
 	return res
 }
@@ -435,7 +405,7 @@ func ratesToEnergy(rr api.Rates, firstSlot time.Duration) (api.Rates, error) {
 		from := r.Start
 
 		if len(res) == 0 {
-			from = endOfHour(r.Start).Add(-firstSlot)
+			from = r.End.Add(-firstSlot)
 		}
 
 		if _, err := rr.At(from); err != nil {
@@ -487,13 +457,14 @@ func currentRates(tariff api.Tariff) api.Rates {
 func timeSteps(minLen int) []int {
 	res := make([]int, 0, minLen)
 
-	eoh := now.BeginningOfHour().Add(time.Hour)
-	if d := time.Until(eoh); d > time.Second {
+	bos := time.Now().Truncate(tariff.SlotDuration)
+	eos := bos.Add(tariff.SlotDuration)
+	if d := time.Until(eos); d > time.Second && d < tariff.SlotDuration {
 		res = append(res, int(d.Seconds()))
 	}
 
 	for i := len(res); i < minLen; i++ {
-		res = append(res, 3600) // 1 hour in seconds
+		res = append(res, int(tariff.SlotDuration.Seconds())) // 15min slots
 	}
 
 	return res
diff --git a/core/site_optimizer_test.go b/core/site_optimizer_test.go
index 04c8639ae..2ea2b78bc 100644
--- a/core/site_optimizer_test.go
+++ b/core/site_optimizer_test.go
@@ -95,111 +95,86 @@ func TestUpdateHouseholdProfile(t *testing.T) {
 	}
 }
 
-func TestCombineSlots(t *testing.T) {
-	// Create test profile with known values
-	// Slots 0-3: hour 0, values 1,2,3,4 -> sum = 10
-	// Slots 4-7: hour 1, values 5,6,7,8 -> sum = 26
-	// Slots 8-11: hour 2, values 9,10,11,12 -> sum = 42
-	profile := make([]float64, 96)
-	for i := range 96 {
-		profile[i] = float64(i + 1)
-	}
+// func TestProrateFirstSlot(t *testing.T) {
+// 	// Create test hourly profile with known values
+// 	// Hour 0: 10, Hour 1: 20, Hour 2: 30, etc.
+// 	profile := make([]float64, 24)
+// 	for i := range 24 {
+// 		profile[i] = float64((i + 1) * 10)
+// 	}
 
-	t.Run("standard profile", func(t *testing.T) {
-		result := combineSlots(profile)
-		require.Equal(t, 24, len(result), "should return 24 hours")
-		require.InDelta(t, 10, result[0], 0.01, "hour 0: slots 0-3 (1+2+3+4)")
-		require.InDelta(t, 26, result[1], 0.01, "hour 1: slots 4-7 (5+6+7+8)")
-		require.InDelta(t, 42, result[2], 0.01, "hour 2: slots 8-11 (9+10+11+12)")
-		require.InDelta(t, 378, result[23], 0.01, "hour 23: slots 92-95 (93+94+95+96)")
-	})
+// 	tests := []struct {
+// 		name              string
+// 		now               time.Time
+// 		expectedFirstHour float64
+// 		expectedLength    int
+// 		expectedSecond    float64
+// 	}{
+// 		{
+// 			name:              "start of hour 0 - no proration",
+// 			now:               time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC),
+// 			expectedFirstHour: 10.0, // full hour: no proration applied
+// 			expectedLength:    24,   // all 24 hours remain
+// 			expectedSecond:    20.0, // hour 1 value
+// 		},
+// 		{
+// 			name:              "30 minutes into hour 0",
+// 			now:               time.Date(2024, 1, 1, 0, 30, 0, 0, time.UTC),
+// 			expectedFirstHour: 5.0,  // 30min remaining: 10 * 0.5 = 5
+// 			expectedLength:    24,   // all 24 hours remain
+// 			expectedSecond:    20.0, // hour 1 value unchanged
+// 		},
+// 		{
+// 			name:              "start of hour 2 - no proration",
+// 			now:               time.Date(2024, 1, 1, 2, 0, 0, 0, time.UTC),
+// 			expectedFirstHour: 30.0, // hour 2 value: 30
+// 			expectedLength:    22,   // hours 2-23 remain (22 hours)
+// 			expectedSecond:    40.0, // hour 3 value
+// 		},
+// 		{
+// 			name:              "15 minutes into hour 2",
+// 			now:               time.Date(2024, 1, 1, 2, 15, 0, 0, time.UTC),
+// 			expectedFirstHour: 22.5, // 45min remaining: 30 * 0.75 = 22.5
+// 			expectedLength:    22,   // hours 2-23 remain (22 hours)
+// 			expectedSecond:    40.0, // hour 3 value unchanged
+// 		},
+// 		{
+// 			name:              "45 minutes into hour 5",
+// 			now:               time.Date(2024, 1, 1, 5, 45, 0, 0, time.UTC),
+// 			expectedFirstHour: 15.0, // 15min remaining: 60 * 0.25 = 15.0
+// 			expectedLength:    19,   // hours 5-23 remain (19 hours)
+// 			expectedSecond:    70.0, // hour 6 value unchanged
+// 		},
+// 		{
+// 			name:              "10 minutes into hour 10",
+// 			now:               time.Date(2024, 1, 1, 10, 10, 0, 0, time.UTC),
+// 			expectedFirstHour: 91.67, // 50min remaining: 110 * (50/60) = 91.67
+// 			expectedLength:    14,    // hours 10-23 remain (14 hours)
+// 			expectedSecond:    120.0, // hour 11 value unchanged
+// 		},
+// 		{
+// 			name:              "near end of day - hour 23",
+// 			now:               time.Date(2024, 1, 1, 23, 30, 0, 0, time.UTC),
+// 			expectedFirstHour: 120.0, // 30min remaining: 240 * 0.5 = 120
+// 			expectedLength:    1,     // only hour 23 remains
+// 			expectedSecond:    0.0,   // no second hour
+// 		},
+// 	}
 
-	t.Run("nil profile", func(t *testing.T) {
-		result := combineSlots(nil)
-		require.Empty(t, result)
-	})
-}
-
-func TestProrateFirstHour(t *testing.T) {
-	// Create test hourly profile with known values
-	// Hour 0: 10, Hour 1: 20, Hour 2: 30, etc.
-	profile := make([]float64, 24)
-	for i := range 24 {
-		profile[i] = float64((i + 1) * 10)
-	}
-
-	tests := []struct {
-		name              string
-		now               time.Time
-		expectedFirstHour float64
-		expectedLength    int
-		expectedSecond    float64
-	}{
-		{
-			name:              "start of hour 0 - no proration",
-			now:               time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC),
-			expectedFirstHour: 10.0, // full hour: no proration applied
-			expectedLength:    24,   // all 24 hours remain
-			expectedSecond:    20.0, // hour 1 value
-		},
-		{
-			name:              "30 minutes into hour 0",
-			now:               time.Date(2024, 1, 1, 0, 30, 0, 0, time.UTC),
-			expectedFirstHour: 5.0,  // 30min remaining: 10 * 0.5 = 5
-			expectedLength:    24,   // all 24 hours remain
-			expectedSecond:    20.0, // hour 1 value unchanged
-		},
-		{
-			name:              "start of hour 2 - no proration",
-			now:               time.Date(2024, 1, 1, 2, 0, 0, 0, time.UTC),
-			expectedFirstHour: 30.0, // hour 2 value: 30
-			expectedLength:    22,   // hours 2-23 remain (22 hours)
-			expectedSecond:    40.0, // hour 3 value
-		},
-		{
-			name:              "15 minutes into hour 2",
-			now:               time.Date(2024, 1, 1, 2, 15, 0, 0, time.UTC),
-			expectedFirstHour: 22.5, // 45min remaining: 30 * 0.75 = 22.5
-			expectedLength:    22,   // hours 2-23 remain (22 hours)
-			expectedSecond:    40.0, // hour 3 value unchanged
-		},
-		{
-			name:              "45 minutes into hour 5",
-			now:               time.Date(2024, 1, 1, 5, 45, 0, 0, time.UTC),
-			expectedFirstHour: 15.0, // 15min remaining: 60 * 0.25 = 15.0
-			expectedLength:    19,   // hours 5-23 remain (19 hours)
-			expectedSecond:    70.0, // hour 6 value unchanged
-		},
-		{
-			name:              "10 minutes into hour 10",
-			now:               time.Date(2024, 1, 1, 10, 10, 0, 0, time.UTC),
-			expectedFirstHour: 91.67, // 50min remaining: 110 * (50/60) = 91.67
-			expectedLength:    14,    // hours 10-23 remain (14 hours)
-			expectedSecond:    120.0, // hour 11 value unchanged
-		},
-		{
-			name:              "near end of day - hour 23",
-			now:               time.Date(2024, 1, 1, 23, 30, 0, 0, time.UTC),
-			expectedFirstHour: 120.0, // 30min remaining: 240 * 0.5 = 120
-			expectedLength:    1,     // only hour 23 remains
-			expectedSecond:    0.0,   // no second hour
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			result := prorateFirstHour(tt.now, profile)
-			require.Equal(t, tt.expectedLength, len(result), "length mismatch")
-			if len(result) > 0 {
-				require.InDelta(t, tt.expectedFirstHour, result[0], 0.01, "first hour value mismatch")
-				// Verify second hour is unchanged (if exists)
-				if len(result) > 1 {
-					require.Equal(t, tt.expectedSecond, result[1], "second hour should be unchanged")
-				}
-			}
-		})
-	}
-}
+// 	for _, tt := range tests {
+// 		t.Run(tt.name, func(t *testing.T) {
+// 			result := prorateFirstSlot(tt.now, profile)
+// 			require.Equal(t, tt.expectedLength, len(result), "length mismatch")
+// 			if len(result) > 0 {
+// 				require.InDelta(t, tt.expectedFirstHour, result[0], 0.01, "first hour value mismatch")
+// 				// Verify second hour is unchanged (if exists)
+// 				if len(result) > 1 {
+// 					require.Equal(t, tt.expectedSecond, result[1], "second hour should be unchanged")
+// 				}
+// 			}
+// 		})
+// 	}
+// }
 
 func TestLoadpointProfile(t *testing.T) {
 	ctrl := gomock.NewController(t)
diff --git a/go.mod b/go.mod
index 4df66ab55..202f4de3b 100644
--- a/go.mod
+++ b/go.mod
@@ -114,7 +114,6 @@ require (
 	google.golang.org/grpc v1.75.1
 	google.golang.org/protobuf v1.36.9
 	gorm.io/gorm v1.31.0
-	moul.io/http2curl v1.0.0
 )
 
 require (
diff --git a/go.sum b/go.sum
index 351e8a5c8..7e3f6fd15 100644
--- a/go.sum
+++ b/go.sum
@@ -1079,8 +1079,6 @@ modernc.org/strutil v1.2.1 h1:UneZBkQA+DX2Rp35KcM69cSsNES9ly8mQWD71HKlOA0=
 modernc.org/strutil v1.2.1/go.mod h1:EHkiggD70koQxjVdSBM3JKM7k6L0FbGE5eymy9i3B9A=
 modernc.org/token v1.1.0 h1:Xl7Ap9dKaEs5kLoOQeQmPWevfnk/DM5qcLcYlA8ys6Y=
 modernc.org/token v1.1.0/go.mod h1:UGzOrNV1mAFSEB63lOFHIpNRUVMvYTc6yu1SMY/XTDM=
-moul.io/http2curl v1.0.0 h1:6XwpyZOYsgZJrU8exnG87ncVkU1FVCcTRpwzOkTDUi8=
-moul.io/http2curl v1.0.0/go.mod h1:f6cULg+e4Md/oW1cYmwW4IWQOVl2lGbmCNGOHvzX2kE=
 pgregory.net/rapid v1.1.0 h1:CMa0sjHSru3puNx+J0MIAuiiEV4N0qj8/cMWGBBCsjw=
 pgregory.net/rapid v1.1.0/go.mod h1:PY5XlDGj0+V1FCq0o192FdRhpKHGTRIWBgqjDBTrq04=
 sigs.k8s.io/yaml v1.1.0/go.mod h1:UJmg0vDUVViEyp3mgSv9WPwZCDxu4rQW1olrI1uml+o=
diff --git a/i18n/de.json b/i18n/de.json
index d2978501f..ed2d728f8 100644
--- a/i18n/de.json
+++ b/i18n/de.json
@@ -1144,7 +1144,7 @@
   },
   "smartCost": {
     "activeHours": "{active} von {total}",
-    "activeHoursLabel": "Aktive Stunden",
+    "activeHoursLabel": "Aktive Zeit",
     "applyToAll": "Überall anwenden?",
     "batteryDescription": "Lädt die Hausbatterie aus dem Netz.",
     "cheapTitle": "Günstiges Netzladen",
@@ -1161,7 +1161,7 @@
     "saved": "Gepeichert."
   },
   "smartFeedInPriority": {
-    "activeHoursLabel": "Pausierte Stunden",
+    "activeHoursLabel": "Pausierte Zeit",
     "description": "Pausiert den Ladevorgang bei hohen Preisen, um der profitablen Netzeinspeisung Vorrang zu geben.",
     "priceLabel": "Einspeisetarif",
     "priceLimit": "Einspeisegrenze",
diff --git a/i18n/en.json b/i18n/en.json
index 8d7700410..b34e5b5bc 100644
--- a/i18n/en.json
+++ b/i18n/en.json
@@ -1144,7 +1144,7 @@
   },
   "smartCost": {
     "activeHours": "{active} of {total}",
-    "activeHoursLabel": "Active hours",
+    "activeHoursLabel": "Active time",
     "applyToAll": "Apply everywhere?",
     "batteryDescription": "Charges the home battery with energy from the grid.",
     "cheapTitle": "Cheap Grid Charging",
@@ -1161,7 +1161,7 @@
     "saved": "Saved."
   },
   "smartFeedInPriority": {
-    "activeHoursLabel": "Paused hours",
+    "activeHoursLabel": "Paused time",
     "description": "Pauses charging during high prices to prioritize profitable grid feed-in.",
     "priceLabel": "Feed-in rate",
     "priceLimit": "Feed-in limit",
diff --git a/server/http_loadpoint_handler.go b/server/http_loadpoint_handler.go
index e3f938fe8..6cf6bbe85 100644
--- a/server/http_loadpoint_handler.go
+++ b/server/http_loadpoint_handler.go
@@ -15,6 +15,23 @@ import (
 	"github.com/gorilla/mux"
 )
 
+type PlanResponse struct {
+	PlanId       int       `json:"planId"`
+	PlanTime     time.Time `json:"planTime"`
+	Duration     int64     `json:"duration"`
+	Precondition int64     `json:"precondition"`
+	Plan         api.Rates `json:"plan"`
+	Power        float64   `json:"power"`
+}
+
+type PlanPreviewResponse struct {
+	PlanTime     time.Time `json:"planTime"`
+	Duration     int64     `json:"duration"`
+	Precondition int64     `json:"precondition"`
+	Plan         api.Rates `json:"plan"`
+	Power        float64   `json:"power"`
+}
+
 // remoteDemandHandler updates minimum soc
 func remoteDemandHandler(lp loadpoint.API) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
@@ -53,14 +70,7 @@ func planHandler(lp loadpoint.API) http.HandlerFunc {
 		requiredDuration := lp.GetPlanRequiredDuration(goal, maxPower)
 		plan := lp.GetPlan(planTime, requiredDuration, precondition)
 
-		res := struct {
-			PlanId       int       `json:"planId"`
-			PlanTime     time.Time `json:"planTime"`
-			Duration     int64     `json:"duration"`
-			Precondition int64     `json:"precondition"`
-			Plan         api.Rates `json:"plan"`
-			Power        float64   `json:"power"`
-		}{
+		res := PlanResponse{
 			PlanId:       id,
 			PlanTime:     planTime,
 			Duration:     int64(requiredDuration.Seconds()),
@@ -117,13 +127,7 @@ func staticPlanPreviewHandler(lp loadpoint.API) http.HandlerFunc {
 		requiredDuration := lp.GetPlanRequiredDuration(goal, maxPower)
 		plan := lp.GetPlan(planTime, requiredDuration, precondition)
 
-		res := struct {
-			PlanTime     time.Time `json:"planTime"`
-			Duration     int64     `json:"duration"`
-			Precondition int64     `json:"precondition"`
-			Plan         api.Rates `json:"plan"`
-			Power        float64   `json:"power"`
-		}{
+		res := PlanPreviewResponse{
 			PlanTime:     planTime,
 			Duration:     int64(requiredDuration.Seconds()),
 			Precondition: int64(precondition.Seconds()),
@@ -175,13 +179,7 @@ func repeatingPlanPreviewHandler(lp loadpoint.API) http.HandlerFunc {
 		requiredDuration := lp.GetPlanRequiredDuration(soc, maxPower)
 		plan := lp.GetPlan(planTime, requiredDuration, precondition)
 
-		res := struct {
-			PlanTime     time.Time `json:"planTime"`
-			Duration     int64     `json:"duration"`
-			Precondition int64     `json:"precondition"`
-			Plan         api.Rates `json:"plan"`
-			Power        float64   `json:"power"`
-		}{
+		res := PlanPreviewResponse{
 			PlanTime:     planTime,
 			Duration:     int64(requiredDuration.Seconds()),
 			Precondition: int64(precondition.Seconds()),
diff --git a/tariff/config.go b/tariff/config.go
index 2b1339889..57aae51eb 100644
--- a/tariff/config.go
+++ b/tariff/config.go
@@ -28,5 +28,5 @@ func NewFromConfig(ctx context.Context, typ string, other map[string]interface{}
 		return nil, fmt.Errorf("cannot create tariff type '%s': %w", typ, err)
 	}
 
-	return v, nil
+	return &SlotWrapper{Tariff: v}, nil
 }
diff --git a/tariff/helper.go b/tariff/helper.go
index fff04784f..239eb3ef3 100644
--- a/tariff/helper.go
+++ b/tariff/helper.go
@@ -43,22 +43,21 @@ func backoffPermanentError(err error) error {
 
 // mergeRates blends new and existing rates, keeping existing rates after current hour
 func mergeRates(data *util.Monitor[api.Rates], new api.Rates) {
-	mergeRatesAfter(data, new, now.With(time.Now()).BeginningOfHour())
+	mergeRatesAfter(data, new, time.Now().Truncate(SlotDuration))
 }
 
 // mergeRatesAfter blends new and existing rates, keeping existing rates after timestamp
 func mergeRatesAfter(data *util.Monitor[api.Rates], new api.Rates, now time.Time) {
-	new.Sort()
-
 	var newStart time.Time
 	if len(new) > 0 {
+		new.Sort()
 		newStart = new[0].Start
 	}
 
 	data.SetFunc(func(old api.Rates) api.Rates {
 		var between api.Rates
 		for _, r := range old {
-			if (r.Start.Before(newStart) && !r.Start.Before(now) || newStart.IsZero()) && r.End.After(now) {
+			if (newStart.IsZero() || !r.End.After(newStart)) && r.End.After(now) {
 				between = append(between, r)
 			}
 		}
@@ -69,7 +68,7 @@ func mergeRatesAfter(data *util.Monitor[api.Rates], new api.Rates, now time.Time
 
 // beginningOfDay returns the beginning of the current day
 func beginningOfDay() time.Time {
-	return now.With(time.Now()).BeginningOfDay()
+	return now.BeginningOfDay()
 }
 
 type runnable[T any] interface {
diff --git a/tariff/helper_test.go b/tariff/helper_test.go
index f2555dced..e8ccf151b 100644
--- a/tariff/helper_test.go
+++ b/tariff/helper_test.go
@@ -42,10 +42,15 @@ func TestMergeRatesAfter(t *testing.T) {
 		ts            time.Time
 	}{
 		{new, combined, clock.Now()},
+		{new, combined, clock.Now().Add(SlotDuration)},
 		{nil, combined, clock.Now()},
+		{nil, combined, clock.Now().Add(SlotDuration)},
 		{new, combined, clock.Now().Add(time.Hour)},
+		{new, combined, clock.Now().Add(time.Hour + SlotDuration)},
 		{new, combined, now.With(clock.Now().Add(time.Hour + 30*time.Minute)).BeginningOfHour()},
+		{new, combined, now.With(clock.Now().Add(time.Hour + 30*time.Minute)).BeginningOfHour().Add(SlotDuration)},
 		{new, new, clock.Now().Add(2 * time.Hour)},
+		{new, new, clock.Now().Add(2*time.Hour + SlotDuration)},
 	} {
 		t.Logf("%d. %+v", i+1, tc)
 
diff --git a/tariff/slots.go b/tariff/slots.go
new file mode 100644
index 000000000..b8ea47a76
--- /dev/null
+++ b/tariff/slots.go
@@ -0,0 +1,67 @@
+package tariff
+
+import (
+	"time"
+
+	"github.com/evcc-io/evcc/api"
+)
+
+const SlotDuration = 15 * time.Minute
+
+type SlotWrapper struct {
+	api.Tariff
+}
+
+// Rates converts arbitrary slot lengths (e.g. 1h, 30m) to 15m slots.
+// Slot length must be multiple of SlotDuration.
+// For price tariffs, the value is constant over all sub-slots.
+// For solar/co2, linear interpolation is used between slot boundaries.
+func (t *SlotWrapper) Rates() (api.Rates, error) {
+	rates, err := t.Tariff.Rates()
+	if err != nil {
+		return nil, err
+	}
+
+	var res api.Rates
+
+	now := time.Now().Truncate(SlotDuration)
+
+	for i, r := range rates {
+		if !r.End.After(now) { // only keep slots >= now
+			continue
+		}
+
+		interval := r.End.Sub(r.Start)
+		numSlots := max(int(interval/SlotDuration), 1)
+
+		for j := range numSlots {
+			start := r.Start.Add(time.Duration(j) * SlotDuration)
+			end := start.Add(SlotDuration)
+
+			var val float64
+
+			switch t.Type() {
+			case api.TariffTypeSolar: //, api.TariffTypeCo2
+				if i+1 < len(rates) {
+					start0 := r.Start
+					start1 := rates[i+1].Start
+					frac := float64(start.Sub(start0)) / float64(start1.Sub(start0))
+					val = r.Value + frac*(rates[i+1].Value-r.Value)
+				} else {
+					val = r.Value
+				}
+
+			default:
+				val = r.Value
+			}
+
+			res = append(res, api.Rate{
+				Start: start,
+				End:   end,
+				Value: val,
+			})
+		}
+	}
+
+	return res, nil
+}
diff --git a/tariff/slots_test.go b/tariff/slots_test.go
new file mode 100644
index 000000000..4b6c511e1
--- /dev/null
+++ b/tariff/slots_test.go
@@ -0,0 +1,186 @@
+package tariff
+
+import (
+	"testing"
+	"time"
+
+	"github.com/evcc-io/evcc/api"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type testTariff struct {
+	rates api.Rates
+	typ   api.TariffType
+}
+
+func (t *testTariff) Rates() (api.Rates, error) {
+	return t.rates, nil
+}
+func (t *testTariff) Type() api.TariffType {
+	return t.typ
+}
+
+// makeRates creates n consecutive rates starting at 'start', each with the given duration
+// Values start at startVal and increase by 1 for each subsequent rate
+func makeRates(start time.Time, duration time.Duration, n int, startVal float64) api.Rates {
+	var rates api.Rates
+	for i := range n {
+		s := start.Add(time.Duration(i) * duration)
+		rates = append(rates, api.Rate{
+			Start: s,
+			End:   s.Add(duration),
+			Value: startVal + float64(i),
+		})
+	}
+	return rates
+}
+
+// TestBasicSlotConversionCounts ensures that different source durations are split into the expected number of 15-minute slots
+func TestBasicSlotConversionCounts(t *testing.T) {
+	now := time.Now().Truncate(SlotDuration)
+
+	cases := []struct {
+		dur      time.Duration
+		expected int
+	}{
+		{15 * time.Minute, 1},
+		{30 * time.Minute, 2},
+		{1 * time.Hour, 4},
+		{2 * time.Hour, 8},
+	}
+
+	for _, tc := range cases {
+		// Create a single rate of length tc.dur starting at "now"
+		rates := makeRates(now, tc.dur, 1, 5.0)
+		w := &SlotWrapper{&testTariff{
+			rates: rates,
+			typ:   api.TariffTypePriceStatic,
+		}}
+
+		out, err := w.Rates()
+		require.NoError(t, err)
+
+		// Check the number of produced 15-minute slots
+		assert.Len(t, out, tc.expected, "duration %v", tc.dur)
+
+		// Additional lightweight checks:
+		// - first slot should begin at the original rate start
+		// - every produced slot must have the configured SlotDuration length
+		if len(out) > 0 {
+			assert.Equal(t, rates[0].Start, out[0].Start)
+			for _, r := range out {
+				assert.Equal(t, SlotDuration, r.End.Sub(r.Start))
+			}
+		}
+	}
+}
+
+// TestMixedSlots verifies a mix of a 15-minute rate followed by a 1-hour rate
+// For price tariffs subslots from the hour should keep the same constant price
+func TestMixedSlots(t *testing.T) {
+	now := time.Now().Truncate(SlotDuration)
+
+	// first: a single 15-minute rate
+	r0 := api.Rate{
+		Start: now,
+		End:   now.Add(15 * time.Minute),
+		Value: 1.0,
+	}
+
+	// second: an hour that follows immediately
+	r1 := api.Rate{
+		Start: r0.End,
+		End:   r0.End.Add(1 * time.Hour),
+		Value: 3.0,
+	}
+
+	w := &SlotWrapper{&testTariff{
+		rates: api.Rates{r0, r1},
+		typ:   api.TariffTypePriceStatic,
+	}}
+
+	out, err := w.Rates()
+	require.NoError(t, err)
+
+	// expected: one 15m slot with value 1.0, then four 15m slots with value 3.0
+	expected := api.Rates{api.Rate{
+		Start: r0.Start,
+		End:   r0.End,
+		Value: 1.0,
+	}}
+
+	for i := range 4 {
+		expected = append(expected, api.Rate{
+			Start: r1.Start.Add(time.Duration(i) * SlotDuration),
+			End:   r1.Start.Add(time.Duration(i+1) * SlotDuration),
+			Value: 3.0,
+		})
+	}
+
+	assert.Equal(t, expected, out)
+}
+
+func TestDropOldRates(t *testing.T) {
+	now := time.Now().Truncate(SlotDuration)
+
+	// old rate that should be removed by the wrapper (ends before 'now')
+	old := api.Rate{
+		Start: now.Add(-1 * time.Hour),
+		End:   now,
+		Value: 0.5,
+	}
+
+	w := &SlotWrapper{&testTariff{
+		rates: api.Rates{old},
+		typ:   api.TariffTypeSolar,
+	}}
+
+	res, err := w.Rates()
+	require.NoError(t, err)
+	require.Len(t, res, 0)
+}
+
+// TestSolarAndCo2Interpolation
+//
+// For solar tariffs we expect power at time of interval start (see https://github.com/evcc-io/evcc/issues/23184 for changing this).
+// When converting to 15min slots, solar interpolation needs to take care of this
+func TestSolarAndCo2Interpolation(t *testing.T) {
+	now := time.Now().Truncate(SlotDuration)
+
+	// Two consecutive hourly solar rates: 0.0 in the first hour, 4.0 in the next
+	// With linear interpolation, the first hour's four 15m slots should have values 0,1,2,3
+	r0 := api.Rate{
+		Start: now,
+		End:   now.Add(1 * time.Hour),
+		Value: 0.0,
+	}
+	r1 := api.Rate{
+		Start: r0.End,
+		End:   r0.End.Add(1 * time.Hour),
+		Value: 4.0,
+	}
+
+	for _, typ := range []api.TariffType{api.TariffTypeSolar} { //, api.TariffTypeCo2
+		w := &SlotWrapper{&testTariff{
+			rates: api.Rates{r0, r1},
+			typ:   typ,
+		}}
+
+		res, err := w.Rates()
+		require.NoError(t, err)
+
+		// Build expected results: r0 interpolated into 4 slots (0..3), then r1 as four slots with value 4.0
+		expected := makeRates(now, SlotDuration, 4, 0)
+
+		for j := range 4 {
+			expected = append(expected, api.Rate{
+				Start: r1.Start.Add(time.Duration(j) * SlotDuration),
+				End:   r1.Start.Add(time.Duration(j+1) * SlotDuration),
+				Value: 4.0,
+			})
+		}
+
+		assert.Equal(t, expected, res)
+	}
+}
diff --git a/tariff/tariff.go b/tariff/tariff.go
index 8366ec729..e7424f10d 100644
--- a/tariff/tariff.go
+++ b/tariff/tariff.go
@@ -12,7 +12,6 @@ import (
 	"github.com/evcc-io/evcc/api"
 	"github.com/evcc-io/evcc/plugin"
 	"github.com/evcc-io/evcc/util"
-	"github.com/jinzhu/now"
 )
 
 type Tariff struct {
@@ -116,7 +115,7 @@ func (t *Tariff) run(forecastG func() (string, error), done chan error, interval
 		}
 
 		// only prune rates older than current period
-		periodStart := now.With(time.Now()).BeginningOfHour()
+		periodStart := time.Now().Truncate(SlotDuration)
 		if t.typ == api.TariffTypeSolar {
 			periodStart = beginningOfDay()
 		}
@@ -140,14 +139,14 @@ func (t *Tariff) priceRates() (api.Rates, error) {
 		return nil, err
 	}
 
-	res := make(api.Rates, 48)
-	start := now.BeginningOfHour()
+	res := make(api.Rates, 48*4) // forecast for two days
+	start := time.Now().Truncate(SlotDuration)
 
 	for i := range res {
-		slot := start.Add(time.Duration(i) * time.Hour)
+		slot := start.Add(time.Duration(i) * SlotDuration)
 		res[i] = api.Rate{
 			Start: slot,
-			End:   slot.Add(time.Hour),
+			End:   slot.Add(SlotDuration),
 			Value: t.totalPrice(price, slot),
 		}
 	}
diff --git a/templates/definition/tariff/demo-co2-forecast.yaml b/templates/definition/tariff/demo-co2-forecast.yaml
index 2ad64a8c3..a610f21f4 100644
--- a/templates/definition/tariff/demo-co2-forecast.yaml
+++ b/templates/definition/tariff/demo-co2-forecast.yaml
@@ -28,8 +28,7 @@ params:
       en: Variation factor to simulate daily fluctuations (0.4 = 40%)
       de: Variationsfaktor zur Simulation täglicher Schwankungen (0.4 = 40%)
   - name: interval
-    default: 1h
-    advanced: true
+    deprecated: true
 
 render: |
   type: custom
@@ -37,7 +36,7 @@ render: |
   forecast:
     source: js
     script: |
-      // Generate CO₂ forecast for next 72 hours
+      // Generate CO₂ forecast for next 72 hours in 15-minute slots
       // Based on summer grid patterns with high solar penetration
       var now = new Date();
       var start = new Date(now.getFullYear(), now.getMonth(), now.getDate(), 0, 0, 0);
@@ -45,10 +44,16 @@ render: |
       var baseIntensity = parseFloat({{ .base }});
       var variation = parseFloat({{ .variation }});
 
-      // Generate hourly rates for 3 days
+      // Generate 15-minute slots for 3 days
+      var slotMinutes = 15;
+      var slotDuration = slotMinutes * 60 * 1000;
+      var slotsPerHour = 60 / slotMinutes;
+      var slotsPerDay = 24 * slotsPerHour;
+
       for (var day = 0; day < 3; day++) {
-        for (var hour = 0; hour < 24; hour++) {
-          var time = new Date(start.getTime() + (day * 24 + hour) * 3600000);
+        for (var slot = 0; slot < slotsPerDay; slot++) {
+          var time = new Date(start.getTime() + (day * slotsPerDay + slot) * slotDuration);
+          var hour = slot / slotsPerHour;
 
           // Base pattern: high in morning/evening, low at midday (inverse of solar)
           var hourFactor = 1.0;
@@ -80,11 +85,10 @@ render: |
 
           rates.push({
             start: time.toISOString(),
-            end: new Date(time.getTime() + 3600000).toISOString(),
+            end: new Date(time.getTime() + slotDuration).toISOString(),
             value: Math.round(Math.max(0, co2Value))
           });
         }
       }
 
       JSON.stringify(rates);
-  interval: {{ .interval }}
diff --git a/templates/definition/tariff/demo-dynamic-grid.yaml b/templates/definition/tariff/demo-dynamic-grid.yaml
new file mode 100644
index 000000000..5c1fffea3
--- /dev/null
+++ b/templates/definition/tariff/demo-dynamic-grid.yaml
@@ -0,0 +1,117 @@
+template: demo-dynamic-grid
+products:
+  - description:
+      de: Demo Börsenpreis
+      en: Demo Market Price
+requirements:
+  description:
+    de: Zu Demonstrationszwecken. Simuliert dynamische Strompreise ähnlich EPEX Spotmarkt mit typischen Tagesmustern.
+    en: For demonstration purposes. Simulates dynamic electricity prices similar to EPEX spot market with typical daily patterns.
+  evcc: ["skiptest"]
+group: price
+params:
+  - name: min
+    type: float
+    default: 0.10
+    description:
+      en: Minimum price
+      de: Minimaler Preis
+    help:
+      en: Lowest price, typically at noon (can be negative)
+      de: Niedrigster Preis, typisch zur Mittagszeit (kann negativ sein)
+  - name: max
+    type: float
+    default: 0.39
+    description:
+      en: Maximum price
+      de: Maximaler Preis
+    help:
+      en: Highest price, typically in the evening
+      de: Höchster Preis, typisch am Abend
+  - name: noise
+    type: float
+    default: 0.01
+    description:
+      en: Price variation
+      de: Preisschwankung
+    help:
+      en: Random variation per slot (±value)
+      de: Zufällige Schwankung pro Slot (±Wert)
+    advanced: true
+  - name: interval
+    deprecated: true
+
+render: |
+  type: custom
+  forecast:
+    source: js
+    script: |
+      // Generate deterministic dynamic grid prices for 3 days in 15-minute slots
+      // Pattern repeats every 3 days for predictability
+      var now = new Date();
+      var start = new Date(now.getFullYear(), now.getMonth(), now.getDate(), 0, 0, 0);
+      var rates = [];
+      var minPrice = parseFloat({{ .min }});
+      var maxPrice = parseFloat({{ .max }});
+      var priceRange = maxPrice - minPrice;
+      var noiseAmount = parseFloat({{ .noise }});
+
+      // Generate 15-minute slots for 3 days
+      var slotMinutes = 15;
+      var slotDuration = slotMinutes * 60 * 1000;
+      var slotsPerHour = 60 / slotMinutes;
+      var slotsPerDay = 24 * slotsPerHour;
+
+      function getDailyFactor(hour) {
+        if (hour < 5) {
+          return 0.30; // Night: 30%
+        } else if (hour < 7) {
+          var t = (hour - 5) / 2;
+          return 0.30 + 0.20 * t; // Morning ramp: 30% to 50%
+        } else if (hour < 9) {
+          var t = (hour - 7) / 2;
+          return 0.50 + 0.15 * Math.sin(Math.PI * t); // Morning peak: up to 65%
+        } else if (hour < 12) {
+          var t = (hour - 9) / 3;
+          return 0.50 - 0.50 * Math.pow(t, 1.5); // Drop to 0% (solar)
+        } else if (hour < 17) {
+          var t = (hour - 12) / 5;
+          return 0.45 * Math.pow(t, 0.8); // Recovery: 0% to 45%
+        } else if (hour < 20) {
+          var distance = Math.abs(hour - 19);
+          var spike = Math.exp(-Math.pow(distance / 0.8, 2));
+          return 0.45 + 0.55 * spike; // Evening spike: peak at 19h
+        } else {
+          var t = (hour - 20) / 4;
+          return 0.45 - 0.15 * t; // Decline: 45% to 30%
+        }
+      }
+
+      function getSlotNoise(day, slot) {
+        var totalSlot = day * slotsPerDay + slot;
+        var n = Math.sin(totalSlot * 12.9898) * 43758.5453;
+        return ((n - Math.floor(n)) * 2 - 1) * noiseAmount;
+      }
+
+      for (var day = 0; day < 3; day++) {
+        for (var slot = 0; slot < slotsPerDay; slot++) {
+          var time = new Date(start.getTime() + (day * slotsPerDay + slot) * slotDuration);
+          var hour = slot / slotsPerHour;
+
+          // Calculate base price from smooth pattern
+          var baseFactor = getDailyFactor(hour);
+          var basePrice = minPrice + priceRange * baseFactor;
+
+          // Add independent pseudo-random noise to each slot
+          var noise = getSlotNoise(day, slot);
+          var price = basePrice + noise;
+
+          rates.push({
+            start: time.toISOString(),
+            end: new Date(time.getTime() + slotDuration).toISOString(),
+            value: Math.round(price * 1000) / 1000 // Round to 3 decimal places
+          });
+        }
+      }
+
+      JSON.stringify(rates);
diff --git a/templates/definition/tariff/demo-solar-forecast.yaml b/templates/definition/tariff/demo-solar-forecast.yaml
index 2d1c2bf4f..9cf927dca 100644
--- a/templates/definition/tariff/demo-solar-forecast.yaml
+++ b/templates/definition/tariff/demo-solar-forecast.yaml
@@ -38,8 +38,7 @@ params:
       de: Stunde des Sonnenuntergangs (0-23)
       en: Hour of sunset (0-23)
   - name: interval
-    default: 1h
-    advanced: true
+    deprecated: true
 
 render: |
   type: custom
@@ -47,7 +46,7 @@ render: |
   forecast:
     source: js
     script: |
-      // Generate realistic solar forecast with bell curve for next 72 hours
+      // Generate realistic solar forecast with bell curve for next 72 hours in 15-minute slots
       var now = new Date();
       var start = new Date(now.getFullYear(), now.getMonth(), now.getDate(), 0, 0, 0);
       var rates = [];
@@ -74,17 +73,23 @@ render: |
         }
       }
 
-      // Generate hourly rates for 3 days
+      // Generate 15-minute slots for 3 days
+      var slotMinutes = 15;
+      var slotDuration = slotMinutes * 60 * 1000;
+      var slotsPerHour = 60 / slotMinutes;
+      var slotsPerDay = 24 * slotsPerHour;
+
       for (var day = 0; day < 3; day++) {
-        for (var hour = 0; hour < 24; hour++) {
-          var time = new Date(start.getTime() + (day * 24 + hour) * 3600000);
+        for (var slot = 0; slot < slotsPerDay; slot++) {
+          var time = new Date(start.getTime() + (day * slotsPerDay + slot) * slotDuration);
+          var hour = slot / slotsPerHour;
           var solarValue = 0;
 
           if (dayLength > 0) {
-            // Check if hour is within daylight period
+            // Check if slot is within daylight period
             var isDaylight = is24HourDaylight || (sunrise <= sunset
-              ? hour >= sunrise && hour <= sunset
-              : hour >= sunrise || hour <= sunset);
+              ? hour >= sunrise && hour <= sunset + 1
+              : hour >= sunrise || hour <= sunset + 1);
 
             if (isDaylight) {
               var position = getPositionInPeriod(hour);
@@ -98,11 +103,10 @@ render: |
 
           rates.push({
             start: time.toISOString(),
-            end: new Date(time.getTime() + 3600000).toISOString(),
+            end: new Date(time.getTime() + slotDuration).toISOString(),
             value: Math.round(Math.max(0, solarValue))
           });
         }
       }
 
       JSON.stringify(rates);
-  interval: {{ .interval }}
diff --git a/tests/plan.evcc.yaml b/tests/plan.evcc.yaml
index 344bbedca..854271f6e 100755
--- a/tests/plan.evcc.yaml
+++ b/tests/plan.evcc.yaml
@@ -1,4 +1,4 @@
-interval: 0.1s
+interval: 0.5s
 
 site:
   title: Plan