diff --git a/.eslintrc.cjs b/.eslintrc.cjs
index c61e31457..6cc3863c6 100644
--- a/.eslintrc.cjs
+++ b/.eslintrc.cjs
@@ -18,5 +18,6 @@ module.exports = {
 		"vue/attribute-hyphenation": "off",
 		"vue/multi-word-component-names": "off",
 		"vue/no-reserved-component-names": "off",
+		"no-param-reassign": "error",
 	},
 };
diff --git a/assets/js/components/Energyflow/Energyflow.vue b/assets/js/components/Energyflow/Energyflow.vue
index e5620d689..772bcdb31 100644
--- a/assets/js/components/Energyflow/Energyflow.vue
+++ b/assets/js/components/Energyflow/Energyflow.vue
@@ -285,8 +285,7 @@ export default {
 		},
 		loadpointsPower: function () {
 			return this.loadpointsCompact.reduce((sum, lp) => {
-				sum += lp.power || 0;
-				return sum;
+				return sum + (lp.power || 0);
 			}, 0);
 		},
 		pvExport: function () {
diff --git a/assets/js/components/Energyflow/EnergyflowEntry.vue b/assets/js/components/Energyflow/EnergyflowEntry.vue
index 4519821d8..6a033d43f 100644
--- a/assets/js/components/Energyflow/EnergyflowEntry.vue
+++ b/assets/js/components/Energyflow/EnergyflowEntry.vue
@@ -124,12 +124,13 @@ export default {
 				}
 				return;
 			}
-			if (!instance) {
-				instance = new Tooltip(ref, { html: true, title: " " });
+			let newInstance = instance;
+			if (!newInstance) {
+				newInstance = new Tooltip(ref, { html: true, title: " " });
 			}
 			const html = `<div class="text-end">${content.join("<br/>")}</div>`;
-			instance.setContent({ ".tooltip-inner": html });
-			return instance;
+			newInstance.setContent({ ".tooltip-inner": html });
+			return newInstance;
 		},
 		powerClicked: function ($event) {
 			if (this.powerTooltip) {
diff --git a/assets/js/components/Savings.vue b/assets/js/components/Savings.vue
index 847101727..9dc5326c9 100644
--- a/assets/js/components/Savings.vue
+++ b/assets/js/components/Savings.vue
@@ -327,8 +327,7 @@ export default {
 				const { rates } = res.data.result;
 				this.referenceGrid =
 					rates.reduce((acc, slot) => {
-						acc += slot.price;
-						return acc;
+						return acc + slot.price;
 					}, 0) / rates.length;
 			} catch (e) {
 				this.referenceGrid = undefined;
diff --git a/assets/js/components/VehicleStatus.vue b/assets/js/components/VehicleStatus.vue
index d2e8d9b6d..e1a3bba16 100644
--- a/assets/js/components/VehicleStatus.vue
+++ b/assets/js/components/VehicleStatus.vue
@@ -626,12 +626,13 @@ export default {
 				}
 				return;
 			}
-			if (!instance) {
+			let newInstance = instance;
+			if (!newInstance) {
 				const trigger = hoverOnly ? "hover" : "hover focus";
-				instance = new Tooltip(ref, { title: " ", trigger });
+				newInstance = new Tooltip(ref, { title: " ", trigger });
 			}
-			instance.setContent({ ".tooltip-inner": content });
-			return instance;
+			newInstance.setContent({ ".tooltip-inner": content });
+			return newInstance;
 		},
 	},
 };
diff --git a/assets/js/mixins/formatter.js b/assets/js/mixins/formatter.js
index ec5d29b4c..bca36bb55 100644
--- a/assets/js/mixins/formatter.js
+++ b/assets/js/mixins/formatter.js
@@ -38,8 +38,10 @@ export default {
       if (val === undefined || val === null) {
         return 0;
       }
-      val = Math.abs(val);
-      return val >= this.fmtLimit ? this.round(val / 1e3, this.fmtDigits) : this.round(val, 0);
+      let absVal = Math.abs(val);
+      return absVal >= this.fmtLimit
+        ? this.round(absVal / 1e3, this.fmtDigits)
+        : this.round(absVal, 0);
     },
     fmtW: function (watt = 0, format = POWER_UNIT.KW, withUnit = true, digits) {
       let unit = format;
@@ -106,10 +108,10 @@ export default {
       if (duration <= 0) {
         return "—";
       }
-      duration = Math.round(duration);
-      var seconds = duration % 60;
-      var minutes = Math.floor(duration / 60) % 60;
-      var hours = Math.floor(duration / 3600);
+      let roundedDuration = Math.round(duration);
+      var seconds = roundedDuration % 60;
+      var minutes = Math.floor(roundedDuration / 60) % 60;
+      var hours = Math.floor(roundedDuration / 3600);
       var result = "";
       let unit = "";
       if (hours >= 1 || minUnit === "h") {