diff --git a/templates/definition/charger/lambda-zewotherm.yaml b/templates/definition/charger/lambda-zewotherm.yaml
index 780c207f4a..320a0ddda3 100644
--- a/templates/definition/charger/lambda-zewotherm.yaml
+++ b/templates/definition/charger/lambda-zewotherm.yaml
@@ -16,17 +16,24 @@ requirements:
       Energiemanagementeinstellungen am Gerät:
 
       - E-Meter Kommunikationsart: "ModBus Client"
-      - E-Meter Messpunkt: "Pos. E-Überschuss"
+      - E-Meter Messpunkt: "Pos. E-Überschuss" oder "Neg. E-Überschuss"
     en: |
       Energy management settings of the device:
 
       - E-Meter communication type: "ModBus Client"
-      - E-Meter measuring point: "Pos. E-Überschuss"
+      - E-Meter measuring point: "Pos. Excess Energy" or "Neg. Excess Energy"
 params:
   - name: host
   - name: tempsource
     type: choice
     choice: ["warmwater_top", "warmwater_bottom", "buffer_top", "buffer_bottom"]
+  - name: excess
+    type: choice
+    choice: ["plus", "minus"]
+    default: "plus"
+    description:
+      de: E-Überschuss ("plus" oder "minus")
+      en: Excess Energy ("plus" or "minus")
   - name: phases
     deprecated: true
   - name: watchdog
@@ -47,6 +54,7 @@ render: |
         address: 102 # PV Überschussleistung
         type: writemultiple # λ erwartet single value als FC16
         decode: int16
+      scale: {{ if eq .excess "plus" }}1{{ else }}-1{{ end }}
   power:
     source: modbus
     uri: {{ .host }}:502
diff --git a/util/modbus/register.go b/util/modbus/register.go
index 4b2f3218a4..6d44f565d6 100644
--- a/util/modbus/register.go
+++ b/util/modbus/register.go
@@ -178,7 +178,12 @@ func (r Register) EncodeFunc() (func(float64) ([]byte, error), error) {
 	case strings.HasPrefix(enc, "bool"):
 		fallthrough
 
-	case strings.HasPrefix(enc, "int") || strings.HasPrefix(enc, "uint"):
+	case strings.HasPrefix(enc, "int"):
+		return r.encodeToBytes(func(v float64) uint64 {
+			return uint64(int64(v))
+		})
+
+	case strings.HasPrefix(enc, "uint"):
 		return r.encodeToBytes(func(v float64) uint64 {
 			return uint64(v)
 		})