From 0744b68336cbe251a818c9bb07ceb738a8b4fa0e Mon Sep 17 00:00:00 2001
From: Michael Geers <michael@geers.tv>
Date: Wed, 3 Sep 2025 08:25:31 +0200
Subject: [PATCH] =?UTF-8?q?HEMS/=C2=A714a:=20visualize=20limit=20state=20(?=
 =?UTF-8?q?#23361)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 assets/js/components/Config/DeviceTags.vue    |   3 +
 assets/js/components/Config/HemsModal.vue     |   4 +-
 .../components/Config/defaultYaml/hems.yaml   |  15 +++
 .../js/components/Energyflow/Energyflow.vue   |  13 +-
 assets/js/components/HemsWarning.vue          |  25 ++++
 assets/js/components/Site/Site.vue            |   5 +
 assets/js/views/Config.vue                    |  37 ++++--
 core/circuit/circuit.go                       |   7 +-
 hems/eebus/eebus.go                           |  25 ++--
 hems/relay/relay.go                           |  24 ++--
 hems/shared/helper.go                         |  30 +++++
 i18n/de.json                                  |  14 ++-
 i18n/en.json                                  |  14 ++-
 tests/fast.evcc.yaml                          |   1 +
 tests/hems.spec.ts                            | 115 ++++++++++++++++++
 tests/simulator.evcc.yaml                     |  13 ++
 tests/simulator/api.ts                        |   1 +
 tests/simulator/src/Simulator.vue             |  18 +++
 tests/vehicle-error.spec.ts                   |   2 +-
 19 files changed, 319 insertions(+), 47 deletions(-)
 create mode 100644 assets/js/components/HemsWarning.vue
 create mode 100644 hems/shared/helper.go
 create mode 100755 tests/fast.evcc.yaml
 create mode 100644 tests/hems.spec.ts

diff --git a/assets/js/components/Config/DeviceTags.vue b/assets/js/components/Config/DeviceTags.vue
index 82e25c83c..36fa3354a 100644
--- a/assets/js/components/Config/DeviceTags.vue
+++ b/assets/js/components/Config/DeviceTags.vue
@@ -55,6 +55,7 @@ export default {
 			switch (name) {
 				case "power":
 				case "solarForecast":
+				case "hemsActiveLimit":
 					return this.fmtW(value);
 				case "energy":
 				case "capacity":
@@ -94,6 +95,8 @@ export default {
 					return value
 						? this.$t("config.deviceValue.yes")
 						: this.$t("config.deviceValue.no");
+				case "hemsType":
+					return this.$t(`config.deviceValueHemsType.${value}`);
 			}
 			return value;
 		},
diff --git a/assets/js/components/Config/HemsModal.vue b/assets/js/components/Config/HemsModal.vue
index b61598b1a..d5f4b26cc 100644
--- a/assets/js/components/Config/HemsModal.vue
+++ b/assets/js/components/Config/HemsModal.vue
@@ -3,11 +3,11 @@
 		id="hemsModal"
 		:title="$t('config.hems.title')"
 		:description="$t('config.hems.description')"
-		docs="/docs/reference/configuration/hems"
+		docs="/docs/features/14a-enwg-steuve"
 		:defaultYaml="defaultYaml"
 		endpoint="/config/hems"
 		removeKey="hems"
-		size="md"
+		data-testid="hems-modal"
 		@changed="$emit('changed')"
 	/>
 </template>
diff --git a/assets/js/components/Config/defaultYaml/hems.yaml b/assets/js/components/Config/defaultYaml/hems.yaml
index cf42b3229..7eebf62c4 100644
--- a/assets/js/components/Config/defaultYaml/hems.yaml
+++ b/assets/js/components/Config/defaultYaml/hems.yaml
@@ -1,3 +1,18 @@
+## external control via binary in put
+
+#type: relay
+#maxPower: 4200 # limit loadpoints to 4.2 kW total
+#limit: # limit signal, plugin
+#  source: mqtt
+#  topic: hems/limit/status # 0/false = normal, 1/true = limit active
+
+## external control via EEBus protocol
+
+#type: eebus # general EEBus setup (cert gen) required
+#ski: "1234-5678-90AB-CDEF" # SKI of control box (grid operator)
+
+## SMA Sunny Home Manager 2.0, will change soon https://github.com/evcc-io/evcc/pull/23190
+
 #type: sma
 #allowcontrol: false
 #vendorid: AAAAAAAA
diff --git a/assets/js/components/Energyflow/Energyflow.vue b/assets/js/components/Energyflow/Energyflow.vue
index 3e1cdcf4f..8293fba73 100644
--- a/assets/js/components/Energyflow/Energyflow.vue
+++ b/assets/js/components/Energyflow/Energyflow.vue
@@ -173,12 +173,7 @@
 							data-testid="energyflow-entry-home"
 						/>
 						<EnergyflowEntry
-							:name="
-								// @ts-ignore
-								$t('main.energyflow.loadpoints', activeLoadpointsCount, {
-									count: activeLoadpointsCount,
-								})
-							"
+							:name="loadpointsLabel"
 							icon="vehicle"
 							:iconProps="{ names: vehicleIcons }"
 							:power="loadpointsPower"
@@ -479,6 +474,12 @@ export default defineComponent({
 		loadpointsExpanded() {
 			return settings.energyflowLoadpoints;
 		},
+		loadpointsLabel() {
+			// @ts-expect-error plural
+			return this.$t("main.energyflow.loadpoints", this.activeLoadpointsCount, {
+				count: this.activeLoadpointsCount,
+			});
+		},
 	},
 	watch: {
 		pvConfigured() {
diff --git a/assets/js/components/HemsWarning.vue b/assets/js/components/HemsWarning.vue
new file mode 100644
index 000000000..738947d97
--- /dev/null
+++ b/assets/js/components/HemsWarning.vue
@@ -0,0 +1,25 @@
+<template>
+	<div v-if="lpcLimit" class="alert alert-warning" data-testid="hems-warning">
+		<strong>{{ $t("main.hemsWarning.title") }}</strong>
+		{{ $t("main.hemsWarning.description", { limit: fmtW(lpcLimit, POWER_UNIT.KW) }) }}
+	</div>
+</template>
+
+<script lang="ts">
+import { defineComponent, type PropType } from "vue";
+import { type Circuit } from "@/types/evcc";
+import formatter from "@/mixins/formatter";
+
+export default defineComponent({
+	name: "HemsWarning",
+	mixins: [formatter],
+	props: {
+		circuits: { type: Object as PropType<Record<string, Circuit>> },
+	},
+	computed: {
+		lpcLimit(): number | null {
+			return this.circuits?.["lpc"]?.maxPower || null;
+		},
+	},
+});
+</script>
diff --git a/assets/js/components/Site/Site.vue b/assets/js/components/Site/Site.vue
index 9e7c5291a..1b409e693 100644
--- a/assets/js/components/Site/Site.vue
+++ b/assets/js/components/Site/Site.vue
@@ -19,6 +19,7 @@
 					<TopNavigation v-bind="topNavigation" />
 				</div>
 			</div>
+			<HemsWarning :circuits="circuits" />
 			<Energyflow v-if="loadpoints.length > 0" v-bind="energyflow" />
 		</div>
 		<div class="d-flex flex-column justify-content-between content-area">
@@ -77,6 +78,7 @@ import "@h2d2/shopicons/es/regular/arrowup";
 import Navigation from "../Top/Navigation.vue";
 import Notifications from "../Top/Notifications.vue";
 import Energyflow from "../Energyflow/Energyflow.vue";
+import HemsWarning from "../HemsWarning.vue";
 import Loadpoints from "../Loadpoints/Loadpoints.vue";
 import Footer from "../Footer/Footer.vue";
 import formatter from "@/mixins/formatter";
@@ -90,6 +92,7 @@ import type {
 	Forecast,
 	LoadpointCompact,
 	Notification,
+	Circuit,
 	SMART_COST_TYPE,
 	Sponsor,
 	FatalError,
@@ -103,6 +106,7 @@ export default defineComponent({
 		Loadpoints,
 		Energyflow,
 		Footer,
+		HemsWarning,
 		Notifications,
 		TopNavigation: Navigation,
 		WelcomeIcons,
@@ -156,6 +160,7 @@ export default defineComponent({
 		smartFeedInPriorityAvailable: Boolean,
 		fatal: { type: Array as PropType<FatalError[]>, default: () => [] },
 		forecast: Object as PropType<Forecast>,
+		circuits: Object as PropType<Record<string, Circuit>>,
 		telemetry: Boolean,
 		evopt: { type: Object as PropType<EvOpt> },
 	},
diff --git a/assets/js/views/Config.vue b/assets/js/views/Config.vue
index ff3bcfae8..db736cf4e 100644
--- a/assets/js/views/Config.vue
+++ b/assets/js/views/Config.vue
@@ -265,11 +265,11 @@
 							<template #icon><CircuitsIcon /></template>
 							<template #tags>
 								<DeviceTags
-									v-if="circuits.length == 0"
+									v-if="circuitsSorted.length == 0"
 									:tags="{ configured: { value: false } }"
 								/>
 								<template
-									v-for="(circuit, idx) in circuits"
+									v-for="(circuit, idx) in circuitsSorted"
 									v-else
 									:key="circuit.name"
 								>
@@ -614,12 +614,21 @@ export default defineComponent({
 			return this.vehicles.map((v) => ({ key: v.name, name: v.config?.title || v.name }));
 		},
 		hemsTags() {
-			const result = { configured: { value: false }, hemsType: {} };
 			const { type } = store.state?.hems || {};
-			if (type) {
-				result.configured.value = true;
-				result.hemsType = { value: type };
+			if (!type) {
+				return { configured: { value: false } };
 			}
+			const result = {
+				hemsType: {},
+				hemsActiveLimit: { value: null as number | null },
+			};
+			result.hemsType = { value: type };
+			const lpc = store.state?.circuits?.["lpc"];
+			if (lpc) {
+				const value = lpc.maxPower || null;
+				result.hemsActiveLimit = { value };
+			}
+
 			return result;
 		},
 		isSponsor() {
@@ -644,6 +653,12 @@ export default defineComponent({
 				authDisabled: store.state?.authDisabled || false,
 			};
 		},
+		circuitsSorted() {
+			const sortedNames = Object.keys(store.state?.circuits || {});
+			return [...this.circuits].sort(
+				(a, b) => sortedNames.indexOf(a.name) - sortedNames.indexOf(b.name)
+			);
+		},
 	},
 	watch: {
 		offline() {
@@ -704,7 +719,15 @@ export default defineComponent({
 		},
 		async loadCircuits() {
 			const response = await api.get("/config/devices/circuit");
-			this.circuits = response.data || [];
+			const circuits = response.data || [];
+			// set lpc default title
+			circuits.forEach((c: ConfigCircuit) => {
+				if (c.name === "lpc" && !c.config?.title) {
+					c.config = c.config || {};
+					c.config.title = this.$t("config.hems.title");
+				}
+			});
+			this.circuits = circuits;
 		},
 		async loadSite() {
 			const response = await api.get("/config/site", {
diff --git a/core/circuit/circuit.go b/core/circuit/circuit.go
index b3461fcc4..d2a7ceff9 100644
--- a/core/circuit/circuit.go
+++ b/core/circuit/circuit.go
@@ -120,7 +120,7 @@ func New(log *util.Logger, title string, maxCurrent, maxPower float64, meter api
 	if maxCurrent == 0 {
 		c.log.DEBUG.Printf("validation of max phase current disabled")
 	} else if _, ok := meter.(api.PhaseCurrents); meter != nil && !ok {
-		return nil, fmt.Errorf("meter does not support phase currents")
+		return nil, errors.New("meter does not support phase currents")
 	}
 
 	return c, nil
@@ -150,7 +150,7 @@ func (c *Circuit) setParent(parent api.Circuit) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	if c.parent != nil {
-		return fmt.Errorf("circuit already has a parent")
+		return errors.New("circuit already has a parent")
 	}
 	c.parent = parent
 	if parent != nil {
@@ -161,6 +161,9 @@ func (c *Circuit) setParent(parent api.Circuit) error {
 
 // Wrap wraps circuit with parent, keeping the original meter
 func (c *Circuit) Wrap(parent api.Circuit) error {
+	if parent == c {
+		return nil // wrap circuit with itself
+	}
 	if c.meter != nil {
 		parent.(*Circuit).meter = c.meter
 	}
diff --git a/hems/eebus/eebus.go b/hems/eebus/eebus.go
index 468721bff..7edd4e470 100644
--- a/hems/eebus/eebus.go
+++ b/hems/eebus/eebus.go
@@ -10,9 +10,9 @@ import (
 	"github.com/evcc-io/evcc/api"
 	"github.com/evcc-io/evcc/core/circuit"
 	"github.com/evcc-io/evcc/core/site"
+	"github.com/evcc-io/evcc/hems/shared"
 	"github.com/evcc-io/evcc/server/eebus"
 	"github.com/evcc-io/evcc/util"
-	"github.com/evcc-io/evcc/util/config"
 )
 
 type EEBus struct {
@@ -32,6 +32,7 @@ type EEBus struct {
 	failsafeDuration time.Duration
 
 	heartbeat *util.Value[struct{}]
+	interval  time.Duration
 }
 
 type Limits struct {
@@ -44,8 +45,9 @@ type Limits struct {
 // New creates an EEBus HEMS from generic config
 func New(ctx context.Context, other map[string]interface{}, site site.API) (*EEBus, error) {
 	cc := struct {
-		Ski    string
-		Limits `mapstructure:",squash"`
+		Ski      string
+		Limits   `mapstructure:",squash"`
+		Interval time.Duration
 	}{
 		Limits: Limits{
 			ContractualConsumptionNominalMax:    24800,
@@ -53,6 +55,7 @@ func New(ctx context.Context, other map[string]interface{}, site site.API) (*EEB
 			FailsafeConsumptionActivePowerLimit: 4200,
 			FailsafeDurationMinimum:             2 * time.Hour,
 		},
+		Interval: 10 * time.Second,
 	}
 
 	if err := util.DecodeOther(other, &cc); err != nil {
@@ -65,28 +68,23 @@ func New(ctx context.Context, other map[string]interface{}, site site.API) (*EEB
 		return nil, errors.New("hems requires load management- please configure root circuit")
 	}
 
-	// create new root circuit for LPC
-	lpc, err := circuit.New(util.NewLogger("lpc"), "eebus", 0, 0, nil, time.Minute)
+	// register LPC circuit if not already registered
+	lpc, err := shared.GetOrCreateCircuit("lpc", "eebus")
 	if err != nil {
 		return nil, err
 	}
 
-	// register LPC-Circuit for use in config, if not already registered
-	if _, err := config.Circuits().ByName("lpc"); err != nil {
-		_ = config.Circuits().Add(config.NewStaticDevice(config.Named{Name: "lpc"}, api.Circuit(lpc)))
-	}
-
 	// wrap old root with new pc parent
 	if err := root.Wrap(lpc); err != nil {
 		return nil, err
 	}
 	site.SetCircuit(lpc)
 
-	return NewEEBus(ctx, cc.Ski, cc.Limits, lpc)
+	return NewEEBus(ctx, cc.Ski, cc.Limits, lpc, cc.Interval)
 }
 
 // NewEEBus creates EEBus charger
-func NewEEBus(ctx context.Context, ski string, limits Limits, root api.Circuit) (*EEBus, error) {
+func NewEEBus(ctx context.Context, ski string, limits Limits, root api.Circuit, interval time.Duration) (*EEBus, error) {
 	if eebus.Instance == nil {
 		return nil, errors.New("eebus not configured")
 	}
@@ -97,6 +95,7 @@ func NewEEBus(ctx context.Context, ski string, limits Limits, root api.Circuit)
 		uc:        eebus.Instance.ControllableSystem(),
 		Connector: eebus.NewConnector(),
 		heartbeat: util.NewValue[struct{}](2 * time.Minute), // LPC-031
+		interval:  interval,
 
 		consumptionLimit: &ucapi.LoadLimit{
 			Value:        limits.ConsumptionLimit,
@@ -149,7 +148,7 @@ func NewEEBus(ctx context.Context, ski string, limits Limits, root api.Circuit)
 }
 
 func (c *EEBus) Run() {
-	for range time.Tick(10 * time.Second) {
+	for range time.Tick(c.interval) {
 		if err := c.run(); err != nil {
 			c.log.ERROR.Println(err)
 		}
diff --git a/hems/relay/relay.go b/hems/relay/relay.go
index e6611fb19..7b098caa0 100644
--- a/hems/relay/relay.go
+++ b/hems/relay/relay.go
@@ -8,9 +8,9 @@ import (
 	"github.com/evcc-io/evcc/api"
 	"github.com/evcc-io/evcc/core/circuit"
 	"github.com/evcc-io/evcc/core/site"
+	"github.com/evcc-io/evcc/hems/shared"
 	"github.com/evcc-io/evcc/plugin"
 	"github.com/evcc-io/evcc/util"
-	"github.com/evcc-io/evcc/util/config"
 )
 
 type Relay struct {
@@ -19,13 +19,17 @@ type Relay struct {
 	root     api.Circuit
 	limit    func() (bool, error)
 	maxPower float64
+	interval time.Duration
 }
 
 // New creates an Relay HEMS from generic config
 func New(ctx context.Context, other map[string]interface{}, site site.API) (*Relay, error) {
-	var cc struct {
+	cc := struct {
 		MaxPower float64
 		Limit    plugin.Config
+		Interval time.Duration
+	}{
+		Interval: 10 * time.Second,
 	}
 
 	if err := util.DecodeOther(other, &cc); err != nil {
@@ -38,17 +42,12 @@ func New(ctx context.Context, other map[string]interface{}, site site.API) (*Rel
 		return nil, errors.New("hems requires load management- please configure root circuit")
 	}
 
-	// create new root circuit for LPC
-	lpc, err := circuit.New(util.NewLogger("lpc"), "relay", 0, 0, nil, time.Minute)
+	// register LPC circuit if not already registered
+	lpc, err := shared.GetOrCreateCircuit("lpc", "relay")
 	if err != nil {
 		return nil, err
 	}
 
-	// register LPC-Circuit for use in config, if not already registered
-	if _, err := config.Circuits().ByName("lpc"); err != nil {
-		_ = config.Circuits().Add(config.NewStaticDevice(config.Named{Name: "lpc"}, api.Circuit(lpc)))
-	}
-
 	// wrap old root with new pc parent
 	if err := root.Wrap(lpc); err != nil {
 		return nil, err
@@ -61,23 +60,24 @@ func New(ctx context.Context, other map[string]interface{}, site site.API) (*Rel
 		return nil, err
 	}
 
-	return NewRelay(lpc, limitG, cc.MaxPower)
+	return NewRelay(lpc, limitG, cc.MaxPower, cc.Interval)
 }
 
 // NewRelay creates Relay HEMS
-func NewRelay(root api.Circuit, limit func() (bool, error), maxPower float64) (*Relay, error) {
+func NewRelay(root api.Circuit, limit func() (bool, error), maxPower float64, interval time.Duration) (*Relay, error) {
 	c := &Relay{
 		log:      util.NewLogger("relay"),
 		root:     root,
 		maxPower: maxPower,
 		limit:    limit,
+		interval: interval,
 	}
 
 	return c, nil
 }
 
 func (c *Relay) Run() {
-	for range time.Tick(10 * time.Second) {
+	for range time.Tick(c.interval) {
 		if err := c.run(); err != nil {
 			c.log.ERROR.Println(err)
 		}
diff --git a/hems/shared/helper.go b/hems/shared/helper.go
new file mode 100644
index 000000000..e00bf95a7
--- /dev/null
+++ b/hems/shared/helper.go
@@ -0,0 +1,30 @@
+package shared
+
+import (
+	"time"
+
+	"github.com/evcc-io/evcc/api"
+	"github.com/evcc-io/evcc/core/circuit"
+	"github.com/evcc-io/evcc/util"
+	"github.com/evcc-io/evcc/util/config"
+)
+
+// GetOrCreateCircuit returns or registers a circuit if not already registered
+func GetOrCreateCircuit(name, title string) (api.Circuit, error) {
+	if dev, err := config.Circuits().ByName(name); err == nil {
+		return dev.Instance(), err
+	}
+
+	// create new circuit
+	circuit, err := circuit.New(util.NewLogger(name), title, 0, 0, nil, time.Minute)
+	if err != nil {
+		return nil, err
+	}
+
+	dev := config.NewStaticDevice[api.Circuit](config.Named{Name: name}, circuit)
+	if err := config.Circuits().Add(dev); err != nil {
+		return nil, err
+	}
+
+	return circuit, nil
+}
diff --git a/i18n/de.json b/i18n/de.json
index c00669b4d..76ddba559 100644
--- a/i18n/de.json
+++ b/i18n/de.json
@@ -99,7 +99,8 @@
       "feedinPrice": "Einspeisevergütung",
       "gridPrice": "Netzpreis",
       "heaterTempLimit": "Heizungslimit",
-      "hemsType": "System",
+      "hemsActiveLimit": "Aktives Limit",
+      "hemsType": "Kommunikation",
       "identifier": "RFID-Kennung",
       "no": "Nein",
       "odometer": "Kilometerstand",
@@ -125,6 +126,10 @@
       "B": "B (verbunden)",
       "C": "C (lädt)"
     },
+    "deviceValueHemsType": {
+      "eebus": "via EEBus",
+      "relay": "via Relais"
+    },
     "devices": {
       "auxMeter": "Smarter Verbraucher",
       "batteryStorage": "Batterie",
@@ -177,7 +182,7 @@
       "titleEdit": "Netzzähler bearbeiten"
     },
     "hems": {
-      "description": "evcc mit einem anderen Heimenergiemanagementsystem verbinden.",
+      "description": "Leistungsbegrenzung durch externe Systeme (bspw. Steuerboxen, § 14a EnWG). Setzt Lastmanagementkonfiguration voraus.",
       "title": "HEMS"
     },
     "icon": {
@@ -721,6 +726,7 @@
       "gridImport": "Netzbezug",
       "homePower": "Verbrauch",
       "loadpoints": "Ladepunkt | Ladepunkt | {count} Ladepunkte",
+      "loadpointsLimit": "{limit} Limit",
       "noEnergy": "Keine Messwerte",
       "pv": "Solaranlage",
       "pvExport": "Einspeisung",
@@ -733,6 +739,10 @@
       "vehicleLimit": "Heizungslimit",
       "waitForVehicle": "Bereit. Warte auf Heizung …"
     },
+    "hemsWarning": {
+      "description": "Reduziere Ladeleistung, um {limit} nicht zu überschreiten.",
+      "title": "Externe Begrenzung:"
+    },
     "loadpoint": {
       "avgPrice": "⌀ Preis",
       "charged": "Geladen",
diff --git a/i18n/en.json b/i18n/en.json
index c3e801627..a9f2cbcd7 100644
--- a/i18n/en.json
+++ b/i18n/en.json
@@ -99,7 +99,8 @@
       "feedinPrice": "Feed-in price",
       "gridPrice": "Grid price",
       "heaterTempLimit": "Heater limit",
-      "hemsType": "System",
+      "hemsActiveLimit": "Active limit",
+      "hemsType": "Communication",
       "identifier": "RFID-Identifier",
       "no": "no",
       "odometer": "Odometer",
@@ -125,6 +126,10 @@
       "B": "B (connected)",
       "C": "C (charging)"
     },
+    "deviceValueHemsType": {
+      "eebus": "via EEBus",
+      "relay": "via Relay"
+    },
     "devices": {
       "auxMeter": "Smart consumer",
       "batteryStorage": "Battery storage",
@@ -177,7 +182,7 @@
       "titleEdit": "Edit Grid Meter"
     },
     "hems": {
-      "description": "Connect evcc to another home energy management system.",
+      "description": "Power limitation by external systems (e.g. EnWG 14a controllers). Requires load management configuration.",
       "title": "HEMS"
     },
     "icon": {
@@ -721,6 +726,7 @@
       "gridImport": "Grid use",
       "homePower": "Consumption",
       "loadpoints": "Charger| Charger | {count} chargers",
+      "loadpointsLimit": "{limit} limit",
       "noEnergy": "No meter data",
       "pv": "Solar system",
       "pvExport": "Grid export",
@@ -733,6 +739,10 @@
       "vehicleLimit": "Heater limit",
       "waitForVehicle": "Ready. Waiting for heater…"
     },
+    "hemsWarning": {
+      "description": "Reduced charging to not exceed {limit}.",
+      "title": "External limit:"
+    },
     "loadpoint": {
       "avgPrice": "⌀ Price",
       "charged": "Charged",
diff --git a/tests/fast.evcc.yaml b/tests/fast.evcc.yaml
new file mode 100755
index 000000000..701278e95
--- /dev/null
+++ b/tests/fast.evcc.yaml
@@ -0,0 +1 @@
+interval: 0.1s
diff --git a/tests/hems.spec.ts b/tests/hems.spec.ts
new file mode 100644
index 000000000..35818f900
--- /dev/null
+++ b/tests/hems.spec.ts
@@ -0,0 +1,115 @@
+import { test, expect } from "@playwright/test";
+import { start, stop, restart, baseUrl } from "./evcc";
+import {
+  expectModalVisible,
+  expectModalHidden,
+  editorClear,
+  editorPaste,
+  enableExperimental,
+  addDemoCharger,
+  newLoadpoint,
+} from "./utils";
+import { startSimulator, stopSimulator, simulatorUrl, simulatorApply } from "./simulator";
+
+test.use({ baseURL: baseUrl() });
+test.describe.configure({ mode: "parallel" });
+
+test.beforeAll(async () => {
+  await startSimulator();
+});
+
+test.afterAll(async () => {
+  await stopSimulator();
+});
+
+test.afterEach(async () => {
+  await stop();
+});
+
+const CONFIG = "fast.evcc.yaml";
+
+test.describe("HEMS", () => {
+  test("configure loadmanagement and hems via UI, verify logic", async ({ page }) => {
+    await start(CONFIG);
+
+    await page.goto("/#/config");
+    await enableExperimental(page);
+
+    // configure circuits
+    await page.getByTestId("circuits").getByRole("button", { name: "edit" }).click();
+    const circuitsModal = page.getByTestId("circuits-modal");
+    await expectModalVisible(circuitsModal);
+    const circuitsEditor = circuitsModal.getByTestId("yaml-editor");
+    await editorClear(circuitsEditor);
+    await editorPaste(circuitsEditor, page, `- name: lpc`);
+    await circuitsModal.getByRole("button", { name: "Save" }).click();
+    await expectModalHidden(circuitsModal);
+
+    // configure hems
+    await page.getByTestId("hems").getByRole("button", { name: "edit" }).click();
+    const hemsModal = page.getByTestId("hems-modal");
+    await expectModalVisible(hemsModal);
+    const hemsEditor = hemsModal.getByTestId("yaml-editor");
+    await editorClear(hemsEditor);
+    await editorPaste(
+      hemsEditor,
+      page,
+      `type: relay
+maxPower: 4200
+interval: 0.1s
+limit:
+  source: http
+  uri: ${simulatorUrl()}/api/state
+  jq: .hems.relay`
+    );
+    await hemsModal.getByRole("button", { name: "Save" }).click();
+    await expectModalHidden(hemsModal);
+
+    await restart(CONFIG);
+    await page.goto("/#/config");
+
+    // configure loadpoint
+    const lpModal = page.getByTestId("loadpoint-modal");
+    await newLoadpoint(page, "Carport");
+    await addDemoCharger(page);
+    await lpModal.getByLabel("Circuit").selectOption("lpc");
+    await lpModal.getByRole("button", { name: "Save" }).click();
+    await expectModalHidden(lpModal);
+    await expect(page.getByTestId("loadpoint")).toContainText("Carport");
+
+    await restart(CONFIG);
+
+    // verify circuits
+    await expect(page.getByTestId("circuits")).toContainText(
+      ["HEMS (lpc)", "Power", "0.0 kW"].join("")
+    );
+
+    // enable hems in simulator
+    await page.goto(simulatorUrl());
+    const hemsRelayCheckbox = page.getByLabel("Relay Limit");
+    await hemsRelayCheckbox.check();
+    await simulatorApply(page);
+
+    // verify config ui
+    await page.goto("/#/config");
+    await expect(page.getByTestId("circuits")).toContainText(
+      ["HEMS (lpc)", "Power", "0.0 kW / 4.2 kW"].join("")
+    );
+
+    // verify main ui
+    await page.getByTestId("home-link").click();
+    const hemsWarning = page.getByTestId("hems-warning");
+    await expect(hemsWarning).toContainText(
+      "External limit: Reduced charging to not exceed 4.2 kW."
+    );
+
+    // disable in simulator
+    await page.goto(simulatorUrl());
+    await hemsRelayCheckbox.uncheck();
+    await simulatorApply(page);
+
+    // verify main ui
+    await page.goto("/");
+    await expect(hemsWarning).not.toBeVisible();
+  });
+});
diff --git a/tests/simulator.evcc.yaml b/tests/simulator.evcc.yaml
index 06935f980..f2583a802 100755
--- a/tests/simulator.evcc.yaml
+++ b/tests/simulator.evcc.yaml
@@ -48,6 +48,7 @@ loadpoints:
     charger: charger
     meter: lp0meter
     mode: pv
+    circuit: lpc
     soc:
       estimate: false
     vehicle: golf
@@ -99,3 +100,15 @@ tariffs:
     zones:
       - hours: 1-6
         price: 0.2
+
+hems:
+  type: relay
+  maxPower: 4200
+  interval: 0.25s
+  limit:
+    source: http
+    uri: http://localhost:7072/api/state
+    jq: .hems.relay
+
+circuits:
+  - name: lpc
diff --git a/tests/simulator/api.ts b/tests/simulator/api.ts
index 7271e5b9f..c0164db96 100644
--- a/tests/simulator/api.ts
+++ b/tests/simulator/api.ts
@@ -10,6 +10,7 @@ let state = {
   },
   loadpoints: [{ power: 0, energy: 0, enabled: false, status: "A" }],
   vehicles: [{ soc: 0, range: 0 }],
+  hems: { relay: false },
 };
 
 const loggingMiddleware = (
diff --git a/tests/simulator/src/Simulator.vue b/tests/simulator/src/Simulator.vue
index 045849869..d68273e0f 100644
--- a/tests/simulator/src/Simulator.vue
+++ b/tests/simulator/src/Simulator.vue
@@ -233,6 +233,23 @@
 		<div class="text-end">
 			<a class="link-primary" href="#" @click.prevent="addVehicle"> add vehicle </a>
 		</div>
+
+		<h4 class="my-4">HEMS</h4>
+		<div class="row">
+			<label for="hemsRelay" class="col-sm-6 col-form-label">Relay Limit</label>
+			<div class="col-sm-6 mb-3">
+				<div class="form-check form-switch">
+					<input
+						id="hemsRelay"
+						v-model="state.hems.relay"
+						class="form-check-input"
+						type="checkbox"
+						role="switch"
+					/>
+					<label class="form-check-label" for="hemsRelay"> active </label>
+				</div>
+			</div>
+		</div>
 		<div class="p-4 text-center fixed-bottom bg-light text-dark bg-opacity-75">
 			<button type="submit" class="btn btn-primary">Apply changes</button>
 		</div>
@@ -260,6 +277,7 @@ export default defineComponent({
 					status: string;
 				}[];
 				vehicles: { soc: number; range: number }[];
+				hems: { relay: boolean };
 			} | null,
 		};
 	},
diff --git a/tests/vehicle-error.spec.ts b/tests/vehicle-error.spec.ts
index b7357c90e..8ec03aab1 100644
--- a/tests/vehicle-error.spec.ts
+++ b/tests/vehicle-error.spec.ts
@@ -28,7 +28,7 @@ test.describe("vehicle startup error (using failing Tesla API)", async () => {
     await expect(page.getByTestId("vehicle-not-reachable-icon")).not.toBeVisible();
   });
 
-  test("broken vehicle: arrival enabeld", async ({ page }) => {
+  test("broken vehicle: arrival enabled", async ({ page }) => {
     await expect(page.getByTestId("vehicle-name")).toHaveText("Broken Tesla");
 
     await page.getByTestId("charging-plan").getByRole("button", { name: "none" }).click();