diff --git a/src/panels/lovelace/cards/energy/common/energy-chart-options.ts b/src/panels/lovelace/cards/energy/common/energy-chart-options.ts
index 0636e4cee3..d49ac755ae 100644
--- a/src/panels/lovelace/cards/energy/common/energy-chart-options.ts
+++ b/src/panels/lovelace/cards/energy/common/energy-chart-options.ts
@@ -295,32 +295,41 @@ export function fillDataGapsAndRoundCaps(datasets: BarSeriesOption[]) {
   });
 }
 
+function getDatapointX(datapoint: NonNullable<LineSeriesOption["data"]>[0]) {
+  const item =
+    datapoint && typeof datapoint === "object" && "value" in datapoint
+      ? datapoint
+      : { value: datapoint };
+  return Number(item.value?.[0]);
+}
+
 export function fillLineGaps(datasets: LineSeriesOption[]) {
   const buckets = Array.from(
     new Set(
       datasets
         .map((dataset) =>
-          dataset.data!.map((datapoint) => Number(datapoint![0]))
+          dataset.data!.map((datapoint) => getDatapointX(datapoint))
         )
         .flat()
     )
   ).sort((a, b) => a - b);
-  buckets.forEach((bucket, index) => {
-    for (let i = datasets.length - 1; i >= 0; i--) {
-      const dataPoint = datasets[i].data![index];
+
+  datasets.forEach((dataset) => {
+    const dataMap = new Map<number, LineDataItemOption>();
+    dataset.data!.forEach((datapoint) => {
       const item: LineDataItemOption =
-        dataPoint && typeof dataPoint === "object" && "value" in dataPoint
-          ? dataPoint
-          : ({ value: dataPoint } as LineDataItemOption);
-      const x = item.value?.[0];
-      if (x === undefined) {
-        continue;
+        datapoint && typeof datapoint === "object" && "value" in datapoint
+          ? datapoint
+          : ({ value: datapoint } as LineDataItemOption);
+      const x = getDatapointX(datapoint);
+      if (!Number.isNaN(x)) {
+        dataMap.set(x, item);
       }
-      if (Number(x) !== bucket) {
-        datasets[i].data?.splice(index, 0, [bucket, 0]);
-      }
-    }
+    });
+
+    dataset.data = buckets.map((bucket) => dataMap.get(bucket) ?? [bucket, 0]);
   });
+
   return datasets;
 }
 
diff --git a/test/panels/lovelace/cards/energy/common/energy-chart-options.test.ts b/test/panels/lovelace/cards/energy/common/energy-chart-options.test.ts
new file mode 100644
index 0000000000..0f1a7dc53c
--- /dev/null
+++ b/test/panels/lovelace/cards/energy/common/energy-chart-options.test.ts
@@ -0,0 +1,199 @@
+import { assert, describe, it } from "vitest";
+import type { LineSeriesOption } from "echarts/charts";
+
+import { fillLineGaps } from "../../../../../../src/panels/lovelace/cards/energy/common/energy-chart-options";
+
+// Helper to get x value from either [x,y] or {value: [x,y]} format
+function getX(item: any): number {
+  return item?.value?.[0] ?? item?.[0];
+}
+
+// Helper to get y value from either [x,y] or {value: [x,y]} format
+function getY(item: any): number {
+  return item?.value?.[1] ?? item?.[1];
+}
+
+describe("fillLineGaps", () => {
+  it("fills gaps in datasets with missing timestamps", () => {
+    const datasets: LineSeriesOption[] = [
+      {
+        type: "line",
+        data: [
+          [1000, 10],
+          [3000, 30],
+        ],
+      },
+      {
+        type: "line",
+        data: [
+          [1000, 100],
+          [2000, 200],
+          [3000, 300],
+        ],
+      },
+    ];
+
+    const result = fillLineGaps(datasets);
+
+    // First dataset should have gap at 2000 filled with 0
+    assert.equal(result[0].data!.length, 3);
+    assert.equal(getX(result[0].data![0]), 1000);
+    assert.equal(getY(result[0].data![0]), 10);
+    assert.equal(getX(result[0].data![1]), 2000);
+    assert.equal(getY(result[0].data![1]), 0);
+    assert.equal(getX(result[0].data![2]), 3000);
+    assert.equal(getY(result[0].data![2]), 30);
+
+    // Second dataset should be unchanged
+    assert.equal(result[1].data!.length, 3);
+    assert.equal(getX(result[1].data![0]), 1000);
+    assert.equal(getY(result[1].data![0]), 100);
+    assert.equal(getX(result[1].data![1]), 2000);
+    assert.equal(getY(result[1].data![1]), 200);
+    assert.equal(getX(result[1].data![2]), 3000);
+    assert.equal(getY(result[1].data![2]), 300);
+  });
+
+  it("handles unsorted data from multiple sources", () => {
+    // This is the bug we're fixing: when multiple power sources are combined,
+    // the data may not be in chronological order
+    const datasets: LineSeriesOption[] = [
+      {
+        type: "line",
+        data: [
+          [3000, 30],
+          [1000, 10],
+          [2000, 20],
+        ],
+      },
+    ];
+
+    const result = fillLineGaps(datasets);
+
+    // Data should be sorted by timestamp
+    assert.equal(result[0].data!.length, 3);
+    assert.equal(getX(result[0].data![0]), 1000);
+    assert.equal(getY(result[0].data![0]), 10);
+    assert.equal(getX(result[0].data![1]), 2000);
+    assert.equal(getY(result[0].data![1]), 20);
+    assert.equal(getX(result[0].data![2]), 3000);
+    assert.equal(getY(result[0].data![2]), 30);
+  });
+
+  it("handles multiple datasets with unsorted data", () => {
+    const datasets: LineSeriesOption[] = [
+      {
+        type: "line",
+        data: [
+          [3000, 30],
+          [1000, 10],
+        ],
+      },
+      {
+        type: "line",
+        data: [
+          [2000, 200],
+          [1000, 100],
+          [3000, 300],
+        ],
+      },
+    ];
+
+    const result = fillLineGaps(datasets);
+
+    // First dataset should be sorted and have gap at 2000 filled
+    assert.equal(result[0].data!.length, 3);
+    assert.equal(getX(result[0].data![0]), 1000);
+    assert.equal(getY(result[0].data![0]), 10);
+    assert.equal(getX(result[0].data![1]), 2000);
+    assert.equal(getY(result[0].data![1]), 0);
+    assert.equal(getX(result[0].data![2]), 3000);
+    assert.equal(getY(result[0].data![2]), 30);
+
+    // Second dataset should be sorted
+    assert.equal(result[1].data!.length, 3);
+    assert.equal(getX(result[1].data![0]), 1000);
+    assert.equal(getY(result[1].data![0]), 100);
+    assert.equal(getX(result[1].data![1]), 2000);
+    assert.equal(getY(result[1].data![1]), 200);
+    assert.equal(getX(result[1].data![2]), 3000);
+    assert.equal(getY(result[1].data![2]), 300);
+  });
+
+  it("handles data with object format (LineDataItemOption)", () => {
+    const datasets: LineSeriesOption[] = [
+      {
+        type: "line",
+        data: [{ value: [3000, 30] }, { value: [1000, 10] }],
+      },
+    ];
+
+    const result = fillLineGaps(datasets);
+
+    assert.equal(result[0].data!.length, 2);
+    assert.equal(getX(result[0].data![0]), 1000);
+    assert.equal(getY(result[0].data![0]), 10);
+    assert.equal(getX(result[0].data![1]), 3000);
+    assert.equal(getY(result[0].data![1]), 30);
+  });
+
+  it("returns empty array for empty datasets", () => {
+    const datasets: LineSeriesOption[] = [
+      {
+        type: "line",
+        data: [],
+      },
+    ];
+
+    const result = fillLineGaps(datasets);
+
+    assert.deepEqual(result[0].data, []);
+  });
+
+  it("handles already sorted data with no gaps", () => {
+    const datasets: LineSeriesOption[] = [
+      {
+        type: "line",
+        data: [
+          [1000, 10],
+          [2000, 20],
+          [3000, 30],
+        ],
+      },
+    ];
+
+    const result = fillLineGaps(datasets);
+
+    assert.equal(result[0].data!.length, 3);
+    assert.equal(getX(result[0].data![0]), 1000);
+    assert.equal(getY(result[0].data![0]), 10);
+    assert.equal(getX(result[0].data![1]), 2000);
+    assert.equal(getY(result[0].data![1]), 20);
+    assert.equal(getX(result[0].data![2]), 3000);
+    assert.equal(getY(result[0].data![2]), 30);
+  });
+
+  it("preserves original data item properties", () => {
+    const datasets: LineSeriesOption[] = [
+      {
+        type: "line",
+        data: [
+          { value: [2000, 20], itemStyle: { color: "red" } },
+          { value: [1000, 10], itemStyle: { color: "blue" } },
+        ],
+      },
+    ];
+
+    const result = fillLineGaps(datasets);
+
+    // First item should be the one with timestamp 1000
+    const firstItem = result[0].data![0] as any;
+    assert.equal(getX(firstItem), 1000);
+    assert.equal(firstItem.itemStyle.color, "blue");
+
+    // Second item should be the one with timestamp 2000
+    const secondItem = result[0].data![1] as any;
+    assert.equal(getX(secondItem), 2000);
+    assert.equal(secondItem.itemStyle.color, "red");
+  });
+});