From e2c59fc6e156cc259b884f929b538d8573eaa690 Mon Sep 17 00:00:00 2001
From: andig <andi@evcc.io>
Date: Thu, 20 Aug 2026 20:14:13 +0200
Subject: [PATCH] Meter (SunSpec): read max AC power from nameplate (#32732)

---
 core/site.go                                  |  4 ++-
 meter/meter.go                                |  4 +--
 meter/meter_test.go                           | 21 +++++++++++++
 meter/usage_battery.go                        |  8 ++---
 meter/usage_pv.go                             | 31 +++++++++++++++----
 .../definition/meter/enphase-modbus.yaml      |  5 ++-
 .../definition/meter/fronius-argeno.yaml      |  3 +-
 templates/definition/meter/fronius-gen24.yaml |  3 +-
 .../definition/meter/fronius-vertoplus.yaml   |  3 +-
 .../meter/kostal-plenticore-gen2.yaml         |  4 +--
 .../definition/meter/solaredge-hybrid.yaml    |  2 +-
 .../definition/meter/solaredge-inverter.yaml  |  1 +
 .../meter/sunspec-hybrid-curtailable.yaml     |  3 +-
 .../definition/meter/sunspec-hybrid.yaml      |  3 +-
 .../meter/sunspec-inverter-curtailable.yaml   |  1 +
 .../definition/meter/sunspec-inverter.yaml    |  1 +
 templates/definition/meter/sunspec.tpl        | 18 +++++++++++
 17 files changed, 91 insertions(+), 24 deletions(-)
 create mode 100644 templates/definition/meter/sunspec.tpl

diff --git a/core/site.go b/core/site.go
index 24e0b2535..d79b786e0 100644
--- a/core/site.go
+++ b/core/site.go
@@ -685,7 +685,9 @@ func (site *Site) updatePvMeters() {
 		}
 
 		if m, ok := api.Cap[api.MaxACPowerGetter](meter); ok {
-			if dc := power - m.MaxACPower(); dc > 0 && power > 0 {
+			// unknown rating (0) must not turn the entire production into excess DC
+			if maxACPower := m.MaxACPower(); maxACPower > 0 && power > maxACPower {
+				dc := power - maxACPower
 				mm[i].ExcessDCPower = dc
 				site.log.DEBUG.Printf("pv %d excess DC: %.0fW", i+1, dc)
 			}
diff --git a/meter/meter.go b/meter/meter.go
index 0a21ef4e3..f11925757 100644
--- a/meter/meter.go
+++ b/meter/meter.go
@@ -24,7 +24,7 @@ func NewConfigurableFromConfig(ctx context.Context, other map[string]any) (api.M
 		measurement.Curtailer `mapstructure:",squash"` // optional
 
 		// pv
-		pvMaxACPower `mapstructure:",squash"`
+		pvMaxACPowerCtx `mapstructure:",squash"`
 
 		// battery
 		batteryCapacityCtx    `mapstructure:",squash"`
@@ -127,7 +127,7 @@ func NewConfigurableFromConfig(ctx context.Context, other map[string]any) (api.M
 	implement.May(m, implement.PhaseCurrents(currentsG))
 	implement.May(m, implement.PhaseVoltages(voltagesG))
 	implement.May(m, implement.PhasePowers(powersG))
-	implement.May(m, implement.MaxACPowerGetter(cc.pvMaxACPower.Decorator()))
+	implement.May(m, implement.MaxACPowerGetter(cc.pvMaxACPowerCtx.Decorator(ctx)))
 
 	return m, nil
 }
diff --git a/meter/meter_test.go b/meter/meter_test.go
index a1d528f90..c33c462a2 100644
--- a/meter/meter_test.go
+++ b/meter/meter_test.go
@@ -22,6 +22,27 @@ func TestPV(t *testing.T) {
 	_, ok := api.Cap[api.MaxACPowerGetter](m)
 	assert.True(t, ok, "MaxACPowerGetter")
 }
+
+func TestPVMaxACPowerPlugin(t *testing.T) {
+	newMeter := func(maxacpower any) api.Meter {
+		m, err := NewConfigurableFromConfig(t.Context(), map[string]any{
+			"power":      map[string]any{"source": "const", "value": 1000},
+			"maxacpower": maxacpower,
+		})
+		require.NoError(t, err)
+		return m
+	}
+
+	m := newMeter(map[string]any{"source": "const", "value": 5000})
+	mp, ok := api.Cap[api.MaxACPowerGetter](m)
+	require.True(t, ok, "MaxACPowerGetter")
+	assert.Equal(t, 5000.0, mp.MaxACPower())
+
+	// device without rating must not be decorated
+	m = newMeter(map[string]any{"source": "error", "error": "ErrNotAvailable"})
+	_, ok = api.Cap[api.MaxACPowerGetter](m)
+	assert.False(t, ok, "MaxACPowerGetter")
+}
 func TestBattery(t *testing.T) {
 	m, err := NewConfigurableFromConfig(t.Context(), map[string]any{
 		"power": map[string]any{
diff --git a/meter/usage_battery.go b/meter/usage_battery.go
index 213ca6428..58524b005 100644
--- a/meter/usage_battery.go
+++ b/meter/usage_battery.go
@@ -43,11 +43,11 @@ func resolveFloat(ctx context.Context, v any) (func() float64, error) {
 	case nil:
 		return nil, nil
 	case int:
-		return staticCapacity(float64(v)), nil
+		return staticFloat(float64(v)), nil
 	case int64:
-		return staticCapacity(float64(v)), nil
+		return staticFloat(float64(v)), nil
 	case float64:
-		return staticCapacity(v), nil
+		return staticFloat(v), nil
 	default:
 		var cfg plugin.Config
 		if err := util.DecodeOther(v, &cfg); err != nil {
@@ -67,7 +67,7 @@ func resolveFloat(ctx context.Context, v any) (func() float64, error) {
 	}
 }
 
-func staticCapacity(f float64) func() float64 {
+func staticFloat(f float64) func() float64 {
 	if f == 0 {
 		return nil
 	}
diff --git a/meter/usage_pv.go b/meter/usage_pv.go
index d578927a9..f8eed6932 100644
--- a/meter/usage_pv.go
+++ b/meter/usage_pv.go
@@ -1,5 +1,11 @@
 package meter
 
+import (
+	"context"
+
+	"github.com/evcc-io/evcc/util"
+)
+
 type pvMaxACPower struct {
 	MaxACPower float64
 }
@@ -8,10 +14,23 @@ type pvMaxACPower struct {
 
 // Decorator returns the max AC power decorator
 func (m *pvMaxACPower) Decorator() func() float64 {
-	if m.MaxACPower == 0 {
-		return nil
-	}
-	return func() float64 {
-		return m.MaxACPower
-	}
+	return staticFloat(m.MaxACPower)
+}
+
+type pvMaxACPowerCtx struct {
+	MaxACPower any // static W value or float plugin
+}
+
+// var _ api.MaxACPowerGetter = (*pvMaxACPowerCtx)(nil)
+
+// Decorator returns the max AC power decorator. MaxACPower may be a static value or a
+// float plugin like the SunSpec nameplate rating. Since the rating is constant, the
+// plugin is read once. Unavailable or zero means not configured.
+func (m *pvMaxACPowerCtx) Decorator(ctx context.Context) func() float64 {
+	get, err := resolveFloat(ctx, m.MaxACPower)
+	if err != nil {
+		// not all devices expose the rating- must not fail configuration
+		util.NewLogger("meter").WARN.Printf("maxacpower: %v", err)
+	}
+	return staticFloat(floatOr0(get))
 }
diff --git a/templates/definition/meter/enphase-modbus.yaml b/templates/definition/meter/enphase-modbus.yaml
index 704deae84..8202b8458 100644
--- a/templates/definition/meter/enphase-modbus.yaml
+++ b/templates/definition/meter/enphase-modbus.yaml
@@ -17,8 +17,7 @@ params:
     choice: ["tcpip"]
     id: 1
   - name: maxacpower
-    service: modbus/read?address=40227&type=holding&encoding=uint16&scale=1&{modbus}
-    usages: ["pv"]
+    deprecated: true # read from nameplate
 render: |
   type: custom
   # sunspec model 701 (DER AC Measurement)
@@ -96,5 +95,5 @@ render: |
         percent = int(limit)
       }
       percent
-  maxacpower: {{ .maxacpower }}
+  {{- include "sunspec-maxacpower" . }}
   {{- end }}
diff --git a/templates/definition/meter/fronius-argeno.yaml b/templates/definition/meter/fronius-argeno.yaml
index 6b36bb851..9a9304c62 100644
--- a/templates/definition/meter/fronius-argeno.yaml
+++ b/templates/definition/meter/fronius-argeno.yaml
@@ -16,6 +16,7 @@ params:
   - name: port
     default: 502
   - name: maxacpower
+    deprecated: true # read from nameplate
 render: |
   type: custom
   # Fronius Argeno: AC output via SunSpec inverter model 113 (float, primary)
@@ -38,4 +39,4 @@ render: |
       - 113:WH
       - 103:WH
     scale: 0.001
-  maxacpower: {{ .maxacpower }} # W
+  {{- include "sunspec-maxacpower-tcp" . }}
diff --git a/templates/definition/meter/fronius-gen24.yaml b/templates/definition/meter/fronius-gen24.yaml
index b9df2c487..219455e4e 100644
--- a/templates/definition/meter/fronius-gen24.yaml
+++ b/templates/definition/meter/fronius-gen24.yaml
@@ -31,6 +31,7 @@ params:
       generic: Integer
     deprecated: true
   - name: maxacpower
+    deprecated: true # read from nameplate
   - preset: battery-params
   - name: maxchargerate
 render: |
@@ -167,7 +168,7 @@ render: |
       id: 1
       value: 160:2:DCWH # mppt 2
       scale: 0.001
-  maxacpower: {{ .maxacpower }} # W
+  {{- include "sunspec-maxacpower-tcp" . }}
   curtail:
     source: sequence
     set:
diff --git a/templates/definition/meter/fronius-vertoplus.yaml b/templates/definition/meter/fronius-vertoplus.yaml
index ca391755b..13b3e27c0 100644
--- a/templates/definition/meter/fronius-vertoplus.yaml
+++ b/templates/definition/meter/fronius-vertoplus.yaml
@@ -18,6 +18,7 @@ params:
       de: "Zähleradresse von Primär- oder Sekundärzählern. Auf der Weboberfläche des Wechselrichters kann nur die Adresse des ersten Zählers (z.B. 200) eingestellt werden. Zusätzliche Zähler erhalten eine aufsteigende Nummer (z.B: 201)."
     usages: ["grid"]
   - name: maxacpower
+    deprecated: true # read from nameplate
   - name: maxchargerate
   - preset: battery-params
 render: |
@@ -163,7 +164,7 @@ render: |
       id: 1
       value: 160:3:DCWH # mppt 3
       scale: 0.001
-  maxacpower: {{ .maxacpower }} # W
+  {{- include "sunspec-maxacpower-tcp" . }}
   {{- end }}
   {{- if eq .usage "battery" }}
   power:
diff --git a/templates/definition/meter/kostal-plenticore-gen2.yaml b/templates/definition/meter/kostal-plenticore-gen2.yaml
index 543f147e7..2cb321e4e 100644
--- a/templates/definition/meter/kostal-plenticore-gen2.yaml
+++ b/templates/definition/meter/kostal-plenticore-gen2.yaml
@@ -35,7 +35,7 @@ params:
     default: little
     advanced: true
   - name: maxacpower
-    service: modbus/read?address=531&type=holding&encoding=uint16&{modbus}
+    deprecated: true # read from nameplate
   - preset: battery-params
   - name: capacity
     service: modbus/read?address=1068&type=holding&encoding=float32s&scale=0.001&{modbus}
@@ -74,7 +74,7 @@ render: |
       type: holding
       encoding: {{ if (eq .endianness "big") }}float32{{ else }}float32s{{ end }}
     scale: 0.001 # Wh -> kWh
-  maxacpower: {{ .maxacpower }} # W
+  {{- include "sunspec-maxacpower" . }}
   # feed-in curtailment via active power limit (SunSpec model 123, WMaxLimPct @ 40217).
   # written as a single register (fn 06); the Plenticore rejects write multiple (fn 16) here.
   # WMaxLim_Ena (register 40221) is enabled by default and left to the inverter
diff --git a/templates/definition/meter/solaredge-hybrid.yaml b/templates/definition/meter/solaredge-hybrid.yaml
index be9b481f7..a8dbb91b8 100644
--- a/templates/definition/meter/solaredge-hybrid.yaml
+++ b/templates/definition/meter/solaredge-hybrid.yaml
@@ -109,7 +109,7 @@ render: |
           address: 0xE174 # Battery 1 Instantaneous Power
           type: holding
           decode: float32nans
-  maxacpower: {{ .maxacpower }} # W
+  {{- include "sunspec-maxacpower" . }}
   curtail:
     source: sequence
     set:
diff --git a/templates/definition/meter/solaredge-inverter.yaml b/templates/definition/meter/solaredge-inverter.yaml
index 6dde3d676..0e4c14205 100644
--- a/templates/definition/meter/solaredge-inverter.yaml
+++ b/templates/definition/meter/solaredge-inverter.yaml
@@ -149,4 +149,5 @@ render: |
         percent = 100
       }
       percent
+  {{- include "sunspec-maxacpower" . }}
   {{- end }}
diff --git a/templates/definition/meter/sunspec-hybrid-curtailable.yaml b/templates/definition/meter/sunspec-hybrid-curtailable.yaml
index c1a686bed..a4a8cdc25 100644
--- a/templates/definition/meter/sunspec-hybrid-curtailable.yaml
+++ b/templates/definition/meter/sunspec-hybrid-curtailable.yaml
@@ -11,6 +11,7 @@ params:
   - name: modbus
     choice: ["tcpip", "rs485"]
   - name: maxacpower
+    deprecated: true # read from nameplate
 render: |
   type: custom
   # sunspec model 203 (int+sf)/ 213 (float) meter
@@ -88,4 +89,4 @@ render: |
         percent = int(limit)
       }
       percent
-  maxacpower: {{ .maxacpower }} # W
+  {{- include "sunspec-maxacpower" . }}
diff --git a/templates/definition/meter/sunspec-hybrid.yaml b/templates/definition/meter/sunspec-hybrid.yaml
index f16e02805..beff62086 100644
--- a/templates/definition/meter/sunspec-hybrid.yaml
+++ b/templates/definition/meter/sunspec-hybrid.yaml
@@ -11,6 +11,7 @@ params:
   - name: modbus
     choice: ["tcpip", "rs485"]
   - name: maxacpower
+    deprecated: true # read from nameplate
   - preset: battery-params
 render: |
   type: custom
@@ -106,7 +107,7 @@ render: |
         {{- include "modbus" . | indent 6 }}
         value: 160:2:DCWH # mppt 2
         scale: 0.001
-  maxacpower: {{ .maxacpower }} # W
+  {{- include "sunspec-maxacpower" . }}
   {{- end }}
   {{- if eq .usage "battery" }}
   power:
diff --git a/templates/definition/meter/sunspec-inverter-curtailable.yaml b/templates/definition/meter/sunspec-inverter-curtailable.yaml
index 4035ffcbf..19d581c33 100644
--- a/templates/definition/meter/sunspec-inverter-curtailable.yaml
+++ b/templates/definition/meter/sunspec-inverter-curtailable.yaml
@@ -87,3 +87,4 @@ render: |
         percent = int(limit)
       }
       percent
+  {{- include "sunspec-maxacpower" . }}
diff --git a/templates/definition/meter/sunspec-inverter.yaml b/templates/definition/meter/sunspec-inverter.yaml
index d3088c229..44b57f50c 100644
--- a/templates/definition/meter/sunspec-inverter.yaml
+++ b/templates/definition/meter/sunspec-inverter.yaml
@@ -153,6 +153,7 @@ render: |
       - 103:WH
       - 113:WH
     scale: 0.001
+  {{- include "sunspec-maxacpower" . }}
   {{- end }}
   {{- if eq .usage "battery" }}
   power:
diff --git a/templates/definition/meter/sunspec.tpl b/templates/definition/meter/sunspec.tpl
new file mode 100644
index 000000000..1d33a273f
--- /dev/null
+++ b/templates/definition/meter/sunspec.tpl
@@ -0,0 +1,18 @@
+{{ define "sunspec-maxacpower" }}
+maxacpower: # nameplate rating
+  source: sunspec
+  {{- include "modbus" . | indent 2 }}
+  value:
+    - 120:WRtg
+    - 702:WMaxRtg
+{{- end }}
+
+{{ define "sunspec-maxacpower-tcp" }}
+maxacpower: # nameplate rating
+  source: sunspec
+  uri: {{ joinHostPort .host .port }}
+  id: 1
+  value:
+    - 120:WRtg
+    - 702:WMaxRtg
+{{- end }}