diff --git a/core/site_optimizer.go b/core/site_optimizer.go
index 701a57e13..2e573ec12 100644
--- a/core/site_optimizer.go
+++ b/core/site_optimizer.go
@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"os"
 	"slices"
+	"sync/atomic"
 	"time"
 
 	evopt "github.com/andig/evopt/client"
@@ -27,6 +28,7 @@ var (
 	batteryPower = float32(6000) // default power of the battery in W
 
 	updated time.Time
+	mu      atomic.Uint32
 )
 
 type batteryType string
@@ -52,8 +54,13 @@ type responseDetails struct {
 func (site *Site) optimizerUpdateAsync(battery []measurement) {
 	var err error
 
+	if !mu.CompareAndSwap(0, 1) {
+		return
+	}
+
 	defer func() {
 		updated = time.Now()
+		mu.Store(0)
 
 		if r := recover(); r != nil {
 			err = fmt.Errorf("panic %v", r)