From 2b87fe2b1da173a25e171a08569002a85377e9d0 Mon Sep 17 00:00:00 2001
From: andig <andi@evcc.io>
Date: Tue, 25 Aug 2026 13:22:49 +0200
Subject: [PATCH] =?UTF-8?q?Gr=C3=BCnstromindex:=20fall=20back=20to=20co2?=
 =?UTF-8?q?=5Fg=5Foekostrom=20when=20co2=5Fg=5Fstandard=20is=20null=20(#33?=
 =?UTF-8?q?164)?=
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Content-Transfer-Encoding: 8bit

---
 tariff/corrently/types.go      |  4 ++--
 tariff/gruenstromindex.go      | 38 ++++++++++++++++++++++++++--------
 tariff/gruenstromindex_test.go | 25 ++++++++++++++++++++++
 3 files changed, 56 insertions(+), 11 deletions(-)
 create mode 100644 tariff/gruenstromindex_test.go

diff --git a/tariff/corrently/types.go b/tariff/corrently/types.go
index c26e10873..4243c1b35 100644
--- a/tariff/corrently/types.go
+++ b/tariff/corrently/types.go
@@ -18,8 +18,8 @@ type Forecast struct {
 		Gsi           float64 `json:"gsi"`
 		TimeStamp     int64   `json:"timeStamp"`
 		Energyprice   string  `json:"energyprice"`
-		Co2GStandard  int     `json:"co2_g_standard"`
-		Co2GOekostrom int     `json:"co2_g_oekostrom"`
+		Co2GStandard  *int    `json:"co2_g_standard"`
+		Co2GOekostrom *int    `json:"co2_g_oekostrom"`
 		Timeframe     struct {
 			Start int64 `json:"start"`
 			End   int64 `json:"end"`
diff --git a/tariff/gruenstromindex.go b/tariff/gruenstromindex.go
index d47968f03..d3cd7b64d 100644
--- a/tariff/gruenstromindex.go
+++ b/tariff/gruenstromindex.go
@@ -74,6 +74,13 @@ func (t *GrünStromIndex) run(done chan error) {
 			}
 		}
 
+		var data api.Rates
+		if err == nil {
+			if data = gsiRates(res); len(data) == 0 {
+				err = api.ErrNotAvailable
+			}
+		}
+
 		if err != nil {
 			if reportError(&once, done, err) {
 				return
@@ -83,20 +90,33 @@ func (t *GrünStromIndex) run(done chan error) {
 			continue
 		}
 
-		data := make(api.Rates, 0, len(res.Forecast))
-		for _, r := range res.Forecast {
-			data = append(data, api.Rate{
-				Start: time.UnixMilli(r.Timeframe.Start).Local(),
-				End:   time.UnixMilli(r.Timeframe.End).Local(),
-				Value: float64(r.Co2GStandard),
-			})
-		}
-
 		mergeRates(t.data, data)
 		once.Do(func() { close(done) })
 	}
 }
 
+// gsiRates maps the forecast to rates. co2_g_standard is null since mid-2026,
+// fall back to co2_g_oekostrom and skip slots without either value.
+func gsiRates(res corrently.Forecast) api.Rates {
+	data := make(api.Rates, 0, len(res.Forecast))
+	for _, r := range res.Forecast {
+		co2 := r.Co2GStandard
+		if co2 == nil {
+			co2 = r.Co2GOekostrom
+		}
+		if co2 == nil {
+			continue
+		}
+
+		data = append(data, api.Rate{
+			Start: time.UnixMilli(r.Timeframe.Start).Local(),
+			End:   time.UnixMilli(r.Timeframe.End).Local(),
+			Value: float64(*co2),
+		})
+	}
+	return data
+}
+
 // Rates implements the api.Tariff interface
 func (t *GrünStromIndex) Rates() (api.Rates, error) {
 	var res api.Rates
diff --git a/tariff/gruenstromindex_test.go b/tariff/gruenstromindex_test.go
new file mode 100644
index 000000000..76b6e8b9e
--- /dev/null
+++ b/tariff/gruenstromindex_test.go
@@ -0,0 +1,25 @@
+package tariff
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/evcc-io/evcc/tariff/corrently"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGsiRates(t *testing.T) {
+	// co2_g_standard is null since mid-2026, co2_g_oekostrom is the fallback
+	var res corrently.Forecast
+	require.NoError(t, json.Unmarshal([]byte(`{"forecast":[
+		{"co2_g_standard":348,"co2_g_oekostrom":23,"timeframe":{"start":1787652000000,"end":1787655600000}},
+		{"co2_g_standard":null,"co2_g_oekostrom":25,"timeframe":{"start":1787655600000,"end":1787659200000}},
+		{"co2_g_standard":null,"co2_g_oekostrom":null,"timeframe":{"start":1787659200000,"end":1787662800000}}
+	]}`), &res))
+
+	rates := gsiRates(res)
+	require.Len(t, rates, 2)
+	assert.Equal(t, 348.0, rates[0].Value)
+	assert.Equal(t, 25.0, rates[1].Value)
+}