fix: price-change fallback trigger no longer goes dead at a zero price

custom_components/battery_controller/const.py

@@ -174,6 +174,9 @@
 PRICE_CHANGE_REOPTIMIZE_THRESHOLD = (
     0.10  # fractional — re-run optimizer on >=10% price change
 )
+PRICE_CHANGE_REOPTIMIZE_ABS_EUR = (
+    0.01  # EUR/kWh — absolute change threshold when the previous price is 0
+)
 STALE_SENSOR_MULTIPLIER = (
     2.0  # x response_time_s — age limit before sensor is treated as stale
 )

custom_components/battery_controller/coordinator_optimization.py

@@ -49,6 +49,7 @@
     MODE_HYBRID,
     MODE_MANUAL,
     MODE_ZERO_GRID,
+    PRICE_CHANGE_REOPTIMIZE_ABS_EUR,
     PRICE_CHANGE_REOPTIMIZE_THRESHOLD,
     STALE_SENSOR_MULTIPLIER,
     BATTERY_MODE_THRESHOLD_W,
@@ -432,13 +433,24 @@ def _handle_price_change(self, event: Event[EventStateChangedData]) -> None:
             self._last_period_start = period_start
             self._schedule_mid_period_run(period_start, interval_minutes)
             self.hass.async_create_task(self.async_request_refresh())
-        elif self._last_price is not None and self._last_price != 0:
+        elif self._last_price is not None:
             # Same period or no timestamp info — fallback threshold check.
-            change_pct = abs(new_price - self._last_price) / abs(self._last_price)
-            if change_pct >= PRICE_CHANGE_REOPTIMIZE_THRESHOLD:
+            if abs(self._last_price) > 1e-9:
+                change_pct = abs(new_price - self._last_price) / abs(self._last_price)
+                significant = change_pct >= PRICE_CHANGE_REOPTIMIZE_THRESHOLD
+            else:
+                # Relative change is undefined at a zero price (free hour):
+                # fall back to an absolute threshold so the trigger does not
+                # go dead — previously the price also never updated from 0,
+                # permanently disabling this fallback path.
+                significant = (
+                    abs(new_price - self._last_price) >= PRICE_CHANGE_REOPTIMIZE_ABS_EUR
+                )
+            if significant:
                 _LOGGER.debug(
-                    "Significant price change: %.2f%%, triggering optimization",
-                    change_pct * 100,
+                    "Significant price change: %.4f -> %.4f, triggering optimization",
+                    self._last_price,
+                    new_price,
                 )
                 self.hass.async_create_task(self.async_request_refresh())
             self._last_price = new_price

tests/test_coordinator_optimization.py

@@ -2830,3 +2830,83 @@ def test_concentrate_redistributes_when_winner_empty(hass):
     result = coord._split_setpoint(-1.0, MODE_ZERO_GRID)
     assert result["bat1"] == pytest.approx(0.0, abs=1e-6)
     assert result["bat2"] == pytest.approx(-1.0, abs=1e-6)
+
+
+@pytest.mark.asyncio
+async def test_price_change_from_zero_uses_absolute_threshold(hass, monkeypatch):
+    """A price moving away from exactly 0 must still trigger re-optimization."""
+    coordinator = _make_coordinator(hass)
+
+    period = datetime(2026, 3, 21, 10, 0, 0, tzinfo=timezone.utc)
+    coordinator._last_price = 0.0  # free hour
+    coordinator._last_period_start = period
+
+    monkeypatch.setattr(
+        "custom_components.battery_controller.coordinator_optimization.extract_price_forecast_with_timestamps",
+        lambda state: ([0.05], [period], 60),
+    )
+    monkeypatch.setattr(
+        "custom_components.battery_controller.coordinator_optimization.dt_util.utcnow",
+        lambda: period + timedelta(minutes=5),
+    )
+
+    refresh_called = []
+
+    async def fake_refresh():
+        refresh_called.append(True)
+
+    monkeypatch.setattr(coordinator, "async_request_refresh", fake_refresh)
+
+    old_mock = MagicMock()
+    old_mock.state = "0.0"
+    new_mock = MagicMock()
+    new_mock.state = "0.05"
+    event = MagicMock()
+    event.data = {"old_state": old_mock, "new_state": new_mock}
+
+    coordinator._handle_price_change(event)
+    await hass.async_block_till_done()
+
+    assert refresh_called, "absolute threshold should trigger from a zero price"
+    assert coordinator._last_price == pytest.approx(0.05)
+
+
+@pytest.mark.asyncio
+async def test_price_change_from_zero_small_change_updates_price(hass, monkeypatch):
+    """Tiny changes from 0 do not trigger, but _last_price must still update."""
+    coordinator = _make_coordinator(hass)
+
+    period = datetime(2026, 3, 21, 10, 0, 0, tzinfo=timezone.utc)
+    coordinator._last_price = 0.0
+    coordinator._last_period_start = period
+
+    monkeypatch.setattr(
+        "custom_components.battery_controller.coordinator_optimization.extract_price_forecast_with_timestamps",
+        lambda state: ([0.001], [period], 60),
+    )
+    monkeypatch.setattr(
+        "custom_components.battery_controller.coordinator_optimization.dt_util.utcnow",
+        lambda: period + timedelta(minutes=5),
+    )
+
+    refresh_called = []
+
+    async def fake_refresh():
+        refresh_called.append(True)
+
+    monkeypatch.setattr(coordinator, "async_request_refresh", fake_refresh)
+
+    old_mock = MagicMock()
+    old_mock.state = "0.0"
+    new_mock = MagicMock()
+    new_mock.state = "0.001"
+    event = MagicMock()
+    event.data = {"old_state": old_mock, "new_state": new_mock}
+
+    coordinator._handle_price_change(event)
+    await hass.async_block_till_done()
+
+    assert not refresh_called
+    # Previously _last_price stayed stuck at 0 because the whole branch was
+    # skipped for a zero price.
+    assert coordinator._last_price == pytest.approx(0.001)