diff --git a/.env.local.example b/.env.local.example
index 33b17a9..5ba8031 100644
--- a/.env.local.example
+++ b/.env.local.example
@@ -11,3 +11,9 @@ INFLUX_ROLLUP_MEASUREMENT=arbeit_hourly
 INFLUX_FIELD=arbeit
 # Umrechnung auf kWh: Zaehlerstand liegt in Wh vor -> 0.001
 INFLUX_UNIT_FACTOR=0.001
+
+# E-Auto-Lade-Erkennung (31d-Diagramm): Leistung (W) laenger als
+# LADEN_MIN_HOURS ununterbrochen ueber LADEN_THRESHOLD_KW -> Tag markiert
+INFLUX_POWER_FIELD=leistung
+LADEN_THRESHOLD_KW=11
+LADEN_MIN_HOURS=2
diff --git a/README.md b/README.md
index 062af1f..3caeab4 100644
--- a/README.md
+++ b/README.md
@@ -60,6 +60,16 @@ from(bucket:"strom")
 
 X-Achse: Datum/Zeit · Y-Achse: kWh
 
+### E-Auto-Lade-Erkennung (31d)
+
+Im 31d-Diagramm werden Tage **rot** markiert, an denen das E-Auto geladen wurde:
+Die Leistung (Feld `leistung`, W) lag **länger als `LADEN_MIN_HOURS` (Default 2 h)
+ununterbrochen über `LADEN_THRESHOLD_KW` (Default 11 kW)** — dem Anschlusswert des
+Autos. Erkennung serverseitig per Flux `stateDuration` auf den Sekundendaten
+(`/api/laden?month=YYYY-MM`); läuft ~15 s je Monat und wird daher gecacht
+(abgeschlossene Monate dauerhaft). Die Markierung wird asynchron nachgeladen,
+sodass die Balken sofort erscheinen. Schwelle/Dauer sind per Env einstellbar.
+
 ## Setup
 
 ```bash
diff --git a/app/api/laden/route.ts b/app/api/laden/route.ts
new file mode 100644
index 0000000..6b73235
--- /dev/null
+++ b/app/api/laden/route.ts
@@ -0,0 +1,28 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { fetchLadetage, LADEN_THRESHOLD_KW, LADEN_MIN_HOURS } from '@/lib/laden';
+
+// GET /api/laden?month=YYYY-MM
+// Liefert die Tage (Tages-Anfangs-Zeitstempel ms), an denen das E-Auto geladen wurde.
+export async function GET(request: NextRequest) {
+  const month = request.nextUrl.searchParams.get('month');
+  if (!month || !/^\d{4}-\d{2}$/.test(month)) {
+    return NextResponse.json(
+      { success: false, error: 'Parameter month=YYYY-MM erforderlich.' },
+      { status: 400 }
+    );
+  }
+
+  try {
+    const days = await fetchLadetage(month);
+    return NextResponse.json(
+      { success: true, days, thresholdKw: LADEN_THRESHOLD_KW, minHours: LADEN_MIN_HOURS },
+      { headers: { 'Cache-Control': 'no-store' } }
+    );
+  } catch (error) {
+    console.error('Laden detection error:', error);
+    return NextResponse.json(
+      { success: false, error: 'Fehler bei der Lade-Erkennung.' },
+      { status: 500 }
+    );
+  }
+}
diff --git a/components/BarChart.tsx b/components/BarChart.tsx
index 76e1a48..a3a658c 100644
--- a/components/BarChart.tsx
+++ b/components/BarChart.tsx
@@ -13,12 +13,24 @@ interface BarChartProps {
   // Optionale feste Achsengrenzen (z.B. komplettes Jahr -> immer 12 Monate sichtbar)
   xMin?: number;
   xMax?: number;
+  // Hervorzuhebende Balken (Zeitstempel-Set, z.B. E-Auto-Ladetage) + Farbe
+  highlight?: Set<number>;
+  highlightColor?: string;
 }
 
 const HOUR_MS = 60 * 60 * 1000;
 const DAY_MS = 24 * HOUR_MS;
 
-export default function BarChart({ title, data, every, color, xMin, xMax }: BarChartProps) {
+export default function BarChart({
+  title,
+  data,
+  every,
+  color,
+  xMin,
+  xMax,
+  highlight,
+  highlightColor = '#c0392b',
+}: BarChartProps) {
   const isHourly = every === '1h';
   const isMonthly = every === '1mo';
   const tooltipDateFormat = isHourly ? '%d.%m.%Y %H:%M' : isMonthly ? '%B %Y' : '%d.%m.%Y';
@@ -76,7 +88,13 @@ export default function BarChart({ title, data, every, color, xMin, xMax }: BarC
       {
         type: 'column',
         name: 'Verbrauch',
-        data,
+        // markierte Balken (z.B. Ladetage) bekommen eine eigene Farbe
+        data:
+          highlight && highlight.size
+            ? data.map(([x, y]) =>
+                highlight.has(x) ? { x, y, color: highlightColor } : { x, y }
+              )
+            : data,
         color,
       },
     ],
diff --git a/components/VerbrauchCharts.tsx b/components/VerbrauchCharts.tsx
index c17fd88..b8fdfac 100644
--- a/components/VerbrauchCharts.tsx
+++ b/components/VerbrauchCharts.tsx
@@ -50,6 +50,32 @@ function ChartCard({ range, every, title, color, selector }: ChartCardProps) {
   const [isLoading, setIsLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
+  // E-Auto-Ladetage (nur 31d): werden asynchron nachgeladen
+  const [ladeDays, setLadeDays] = useState<Set<number>>(new Set());
+  const [ladeLoading, setLadeLoading] = useState(false);
+  const [ladeMeta, setLadeMeta] = useState<{ thresholdKw: number; minHours: number } | null>(null);
+
+  const fetchLaden = useCallback(
+    async (sel: string) => {
+      if (range !== '31d') return;
+      setLadeLoading(true);
+      setLadeDays(new Set());
+      try {
+        const res = await fetch(`/api/laden?month=${sel}`, { cache: 'no-store' });
+        const json = await res.json();
+        if (json.success) {
+          setLadeDays(new Set<number>(json.days));
+          setLadeMeta({ thresholdKw: json.thresholdKw, minHours: json.minHours });
+        }
+      } catch {
+        // Markierung ist sekundaer -> Fehler still ignorieren
+      } finally {
+        setLadeLoading(false);
+      }
+    },
+    [range]
+  );
+
   const fetchData = useCallback(
     async (sel: string) => {
       setIsLoading(true);
@@ -83,9 +109,15 @@ function ChartCard({ range, every, title, color, selector }: ChartCardProps) {
 
   useEffect(() => {
     fetchData(value);
+    fetchLaden(value);
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, []);
 
+  const handleApply = () => {
+    fetchData(value);
+    fetchLaden(value);
+  };
+
   // Jahres-Chart: Achse immer ueber das komplette Kalenderjahr -> alle 12 Monate
   // sichtbar, Restmonate bleiben ohne Balken.
   let xMin: number | undefined;
@@ -138,7 +170,7 @@ function ChartCard({ range, every, title, color, selector }: ChartCardProps) {
         </div>
 
         <button
-          onClick={() => fetchData(value)}
+          onClick={handleApply}
           disabled={isLoading}
           className="bg-[#85B7D7] hover:bg-[#6a9fc5] px-5 py-2 text-sm rounded-lg transition-colors shadow-md disabled:opacity-50"
         >
@@ -156,13 +188,36 @@ function ChartCard({ range, every, title, color, selector }: ChartCardProps) {
         <div className="text-center py-16 text-gray-500">Lade Daten…</div>
       ) : (
         <>
-          <BarChart title={title} data={data} every={every} color={color} xMin={xMin} xMax={xMax} />
-          {data.length > 0 && (
-            <div className="text-right text-sm font-semibold mt-2 px-2">
-              {totalLabel}:{' '}
-              {total.toLocaleString('de-DE', { minimumFractionDigits: 1, maximumFractionDigits: 1 })} kWh
-            </div>
-          )}
+          <BarChart
+            title={title}
+            data={data}
+            every={every}
+            color={color}
+            xMin={xMin}
+            xMax={xMax}
+            highlight={range === '31d' ? ladeDays : undefined}
+          />
+          <div className="flex justify-between items-center mt-2 px-2 text-sm">
+            {/* Legende: E-Auto-Ladetage (nur 31d) */}
+            {range === '31d' ? (
+              <span className="text-gray-600 flex items-center gap-1.5">
+                <span className="inline-block w-3 h-3 rounded-sm" style={{ backgroundColor: '#c0392b' }} />
+                {ladeLoading
+                  ? 'E-Auto-Ladung wird geprüft…'
+                  : ladeDays.size > 0
+                    ? `E-Auto geladen (> ${ladeMeta?.thresholdKw ?? ''} kW, ≥ ${ladeMeta?.minHours ?? ''} h)`
+                    : 'Keine E-Auto-Ladung erkannt'}
+              </span>
+            ) : (
+              <span />
+            )}
+            {data.length > 0 && (
+              <span className="font-semibold whitespace-nowrap">
+                {totalLabel}:{' '}
+                {total.toLocaleString('de-DE', { minimumFractionDigits: 1, maximumFractionDigits: 1 })} kWh
+              </span>
+            )}
+          </div>
         </>
       )}
     </div>
diff --git a/lib/laden.ts b/lib/laden.ts
new file mode 100644
index 0000000..3c7006e
--- /dev/null
+++ b/lib/laden.ts
@@ -0,0 +1,91 @@
+import { InfluxDB } from '@influxdata/influxdb-client';
+import { resolveRange } from '@/lib/ranges';
+
+const URL = process.env.INFLUX_URL || 'http://nuccy:8086';
+const TOKEN = process.env.INFLUX_TOKEN || '';
+const ORG = process.env.INFLUX_ORG || 'citysensor';
+const BUCKET = process.env.INFLUX_BUCKET || 'strom';
+const MEASUREMENT = process.env.INFLUX_MEASUREMENT || 'vzlogger';
+const POWER_FIELD = process.env.INFLUX_POWER_FIELD || 'leistung'; // momentane Leistung in W
+const TZ = process.env.INFLUX_TZ || 'Europe/Berlin';
+
+// E-Auto-Ladung: Leistung laenger als MIN_HOURS ununterbrochen ueber THRESHOLD_KW
+export const LADEN_THRESHOLD_KW = parseFloat(process.env.LADEN_THRESHOLD_KW || '11');
+export const LADEN_MIN_HOURS = parseFloat(process.env.LADEN_MIN_HOURS || '2');
+
+const influx = new InfluxDB({ url: URL, token: TOKEN, timeout: 90_000 });
+
+interface CacheEntry {
+  days: number[];
+  cachedAt: number;
+}
+const cache = new Map<string, CacheEntry>();
+const CURRENT_MONTH_TTL = 5 * 60 * 1000; // laufender Monat: 5 min; abgeschlossene Monate: dauerhaft
+
+function isCurrentMonth(month: string): boolean {
+  const now = new Date();
+  const cur = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}`;
+  return month >= cur;
+}
+
+/**
+ * Ermittelt die Tage eines Monats, an denen das E-Auto geladen wurde:
+ * Leistung (`leistung`, W) lag laenger als LADEN_MIN_HOURS ununterbrochen ueber
+ * LADEN_THRESHOLD_KW. Rueckgabe = Tages-Anfangs-Zeitstempel (ms, Berliner Tag),
+ * passend zu den x-Werten der 31d-Balken.
+ *
+ * Erkennung serverseitig per Flux `stateDuration` (laeuft je Monat ~10-15s auf
+ * den Sekundendaten), daher Caching: abgeschlossene Monate dauerhaft.
+ */
+export async function fetchLadetage(month: string): Promise<number[]> {
+  const thresholdW = LADEN_THRESHOLD_KW * 1000;
+  const minSeconds = Math.round(LADEN_MIN_HOURS * 3600);
+  const key = `${month}|${thresholdW}|${minSeconds}`;
+
+  const hit = cache.get(key);
+  if (hit && (!isCurrentMonth(month) || Date.now() - hit.cachedAt < CURRENT_MONTH_TTL)) {
+    return hit.days;
+  }
+
+  const { start, stop } = resolveRange('31d', { month });
+  // 24h Vorlauf, damit ueber Mitternacht laufende Ladungen am Monatsanfang
+  // korrekt erkannt werden (stateDuration startet sonst erst an der Range-Grenze).
+  const queryStart = new Date(start.getTime() - 24 * 3600 * 1000);
+
+  const flux = `
+import "timezone"
+option location = timezone.location(name: "${TZ}")
+
+threshold = ${thresholdW}.0
+
+from(bucket: "${BUCKET}")
+  |> range(start: ${queryStart.toISOString()}, stop: ${stop.toISOString()})
+  |> filter(fn: (r) => r._measurement == "${MEASUREMENT}")
+  |> filter(fn: (r) => r._field == "${POWER_FIELD}")
+  |> stateDuration(fn: (r) => r._value > threshold, unit: 1s)
+  |> filter(fn: (r) => r.stateDuration >= ${minSeconds})
+  |> aggregateWindow(every: 1d, fn: max, createEmpty: false)
+  |> timeShift(duration: -1d)
+  |> keep(columns: ["_time"])
+`;
+
+  const queryApi = influx.getQueryApi(ORG);
+  const minTs = start.getTime();
+  const maxTs = stop.getTime();
+  const days: number[] = [];
+
+  await new Promise<void>((resolve, reject) => {
+    queryApi.queryRows(flux, {
+      next(row, tableMeta) {
+        const o = tableMeta.toObject(row);
+        const ts = new Date(o._time as string).getTime();
+        if (ts >= minTs && ts < maxTs) days.push(ts);
+      },
+      error: reject,
+      complete: resolve,
+    });
+  });
+
+  cache.set(key, { days, cachedAt: Date.now() });
+  return days;
+}