diff --git a/core/site_optimizer.go b/core/site_optimizer.go
index 3952062ba..d19de7f86 100644
--- a/core/site_optimizer.go
+++ b/core/site_optimizer.go
@@ -413,8 +413,7 @@ func (site *Site) optimizerRequest(battery []types.Measurement) (optimizer.Optim
 	}
 
 	if optimizerURI() == OPTIMIZER_URI {
-		// limit to 2 days for sake of performance
-		minLen = min(2*96, minLen)
+		minLen = slotsUntil(grid, optimizerHorizon(time.Now()), minLen)
 	}
 
 	if expectedSlots := 8; minLen < expectedSlots {
@@ -1127,6 +1126,27 @@ func currentRates(tariff api.Tariff) api.Rates {
 	})
 }
 
+// optimizerHorizon is the timeframe the hosted optimizer is limited to for sake
+// of performance: 48 hours, extended to the end of that day. In the early hours
+// the extension would add almost a full day, hence it only applies past 6:00.
+func optimizerHorizon(t time.Time) time.Time {
+	horizon := t.Add(48 * time.Hour)
+	if t.Hour() < 6 {
+		return horizon
+	}
+	return now.With(horizon).EndOfDay()
+}
+
+// slotsUntil limits maxLen to the slots starting before the given horizon
+func slotsUntil(rates api.Rates, horizon time.Time, maxLen int) int {
+	if i := slices.IndexFunc(rates[:min(maxLen, len(rates))], func(slot api.Rate) bool {
+		return slot.Start.After(horizon)
+	}); i >= 0 {
+		return i
+	}
+	return maxLen
+}
+
 func timeSteps(minLen int, now time.Time) []int {
 	res := make([]int, 0, minLen)
 
diff --git a/core/site_optimizer_test.go b/core/site_optimizer_test.go
index 446e8889c..94c99e743 100644
--- a/core/site_optimizer_test.go
+++ b/core/site_optimizer_test.go
@@ -7,6 +7,7 @@ import (
 	"github.com/evcc-io/evcc/api"
 	"github.com/evcc-io/evcc/core/loadpoint"
 	"github.com/evcc-io/evcc/core/types"
+	"github.com/evcc-io/evcc/tariff"
 	"github.com/evcc-io/evcc/util"
 	"github.com/evcc-io/evcc/util/config"
 	optimizer "github.com/evcc-io/optimizer/client"
@@ -29,6 +30,30 @@ func TestLoadpointProfile(t *testing.T) {
 	require.Equal(t, []float64{250, 250, 250, 250, 250, 250, 250, 50}, loadpointProfile(lp, 8))
 }
 
+func TestOptimizerHorizon(t *testing.T) {
+	ts := time.Date(2025, 1, 1, 10, 30, 0, 0, time.Local)
+	horizon := optimizerHorizon(ts)
+
+	// 48h plus end of day
+	assert.Equal(t, time.Date(2025, 1, 3, 23, 59, 59, int(time.Second-time.Nanosecond), time.Local), horizon)
+
+	// before 6:00 the day is not extended
+	assert.Equal(t, time.Date(2025, 1, 3, 5, 30, 0, 0, time.Local),
+		optimizerHorizon(time.Date(2025, 1, 1, 5, 30, 0, 0, time.Local)))
+
+	rates := make(api.Rates, 0, 4*96)
+	for slot := ts.Truncate(tariff.SlotDuration); len(rates) < cap(rates); slot = slot.Add(tariff.SlotDuration) {
+		rates = append(rates, api.Rate{Start: slot, End: slot.Add(tariff.SlotDuration)})
+	}
+
+	// 4 days of slots from 10:30, capped at the last slot of Jan 3rd
+	assert.Equal(t, 246, slotsUntil(rates, horizon, len(rates)))
+	assert.Equal(t, time.Date(2025, 1, 3, 23, 45, 0, 0, time.Local), rates[245].Start)
+
+	// shorter forecast is not extended
+	assert.Equal(t, 8, slotsUntil(rates, horizon, 8))
+}
+
 func TestApplyPrecondition(t *testing.T) {
 	ctrl := gomock.NewController(t)