diff --git a/server/http_config_device_handler.go b/server/http_config_device_handler.go
index e131d6970..f3315233e 100644
--- a/server/http_config_device_handler.go
+++ b/server/http_config_device_handler.go
@@ -101,7 +101,6 @@ func deviceConfigMap[T any](class templates.Class, dev config.Device[T]) (map[st
 		}
 
 		if conf.Type == typeTemplate {
-			// template device, mask config
 			params, err := sanitizeMasked(class, conf.Other)
 			if err != nil {
 				return nil, err
diff --git a/server/http_config_helper.go b/server/http_config_helper.go
index a22d754df..7ea912ff0 100644
--- a/server/http_config_helper.go
+++ b/server/http_config_helper.go
@@ -26,7 +26,9 @@ const (
 	masked       = "***"      // masked indicates a masked config parameter value
 )
 
-var customTypes = []string{"custom", "template", "heatpump", "switchsocket", "sgready", "sgready-boost"}
+var (
+	customTypes = []string{"custom", "template", "heatpump", "switchsocket", "sgready", "sgready-boost"}
+)
 
 type configReq struct {
 	config.Properties `json:",inline" mapstructure:",squash"`
@@ -105,6 +107,23 @@ func templateForConfig(class templates.Class, conf map[string]any) (templates.Te
 	return templates.ByName(class, typ)
 }
 
+func filterValidTemplateParams(tmpl *templates.Template, conf map[string]any) map[string]any {
+	res := make(map[string]any)
+
+	for k, v := range conf {
+		if k == "template" {
+			res[k] = v
+			continue
+		}
+
+		if i, _ := tmpl.ParamByName(k); i >= 0 {
+			res[k] = v
+		}
+	}
+
+	return res
+}
+
 func sanitizeMasked(class templates.Class, conf map[string]any) (map[string]any, error) {
 	tmpl, err := templateForConfig(class, conf)
 	if err != nil {
@@ -121,7 +140,7 @@ func sanitizeMasked(class templates.Class, conf map[string]any) (map[string]any,
 		res[k] = v
 	}
 
-	return res, nil
+	return filterValidTemplateParams(&tmpl, res), nil
 }
 
 func mergeMasked(class templates.Class, conf, old map[string]any) (map[string]any, error) {
@@ -140,7 +159,7 @@ func mergeMasked(class templates.Class, conf, old map[string]any) (map[string]an
 		res[k] = v
 	}
 
-	return res, nil
+	return filterValidTemplateParams(&tmpl, res), nil
 }
 
 func startDeviceTimeout() (context.Context, context.CancelFunc, chan struct{}) {
diff --git a/server/http_config_helper_test.go b/server/http_config_helper_test.go
index 4cd433437..9db781d87 100644
--- a/server/http_config_helper_test.go
+++ b/server/http_config_helper_test.go
@@ -7,6 +7,7 @@ import (
 	"github.com/evcc-io/evcc/api/globalconfig"
 	"github.com/evcc-io/evcc/plugin/mqtt"
 	"github.com/evcc-io/evcc/util/config"
+	"github.com/evcc-io/evcc/util/templates"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -134,3 +135,47 @@ func TestSquashedMergeMaskedAny(t *testing.T) {
 		assert.Equal(t, "new", new.User)
 	}
 }
+
+func TestMergeMaskedFiltersBehavior(t *testing.T) {
+	conf := map[string]any{
+		"template": "demo-meter",
+		"power":    200.0,
+	}
+
+	old := map[string]any{
+		"template":      "demo-meter",
+		"power":         100.0,
+		"outdatedField": "old-value",
+	}
+
+	result, err := mergeMasked(templates.Meter, conf, old)
+	require.NoError(t, err)
+
+	assert.Equal(t, 200.0, result["power"])
+	assert.Equal(t, "demo-meter", result["template"])
+	assert.NotContains(t, result, "outdatedField")
+}
+
+func TestFilterValidTemplateParams(t *testing.T) {
+	conf := map[string]any{
+		"template":      "generic",
+		"usage":         "grid",
+		"capacity":      50.0,
+		"power":         100.0,
+		"outdatedField": "should-be-removed",
+	}
+
+	result := filterValidTemplateParams(&templates.Template{
+		TemplateDefinition: templates.TemplateDefinition{
+			Params: []templates.Param{
+				{Name: "usage"},
+				{Name: "power"},
+				{Name: "capacity"},
+			},
+		},
+	}, conf)
+
+	assert.Equal(t, "generic", result["template"], "template")
+	assert.Equal(t, "grid", result["usage"], "usage")
+	assert.NotContains(t, result, "outdatedField")
+}
diff --git a/tests/config-invalid-template.spec.ts b/tests/config-invalid-template.spec.ts
new file mode 100644
index 000000000..51643b9b0
--- /dev/null
+++ b/tests/config-invalid-template.spec.ts
@@ -0,0 +1,46 @@
+import { test, expect } from "@playwright/test";
+import { start, stop, restart, baseUrl } from "./evcc";
+import { expectModalVisible, expectModalHidden, enableExperimental } from "./utils";
+
+const CONFIG_INVALID_TEMPLATE = "config-invalid-template.sql";
+
+test.use({ baseURL: baseUrl() });
+
+test.afterEach(async () => {
+  await stop();
+});
+
+test.describe("invalid template migration", async () => {
+  test("fix broken grid meter with outdated field", async ({ page }) => {
+    await start(undefined, CONFIG_INVALID_TEMPLATE);
+
+    await page.goto("/#/config");
+    await enableExperimental(page, false);
+
+    // startup error
+    await expect(page.getByTestId("fatal-error")).toBeVisible();
+    await expect(page.getByTestId("fatal-error")).toContainText("invalid key: power_old");
+    await expect(page.getByTestId("grid")).toBeVisible();
+
+    // edit and save broken meter
+    await page.getByTestId("grid").getByRole("button", { name: "edit" }).click();
+    const meterModal = page.getByTestId("meter-modal");
+    await expectModalVisible(meterModal);
+    await expect(meterModal.getByLabel("Manufacturer")).toHaveValue("Demo meter");
+    await meterModal.getByLabel("Power").fill("222");
+    await meterModal.getByRole("button", { name: "Validate & save" }).click();
+    await expectModalHidden(meterModal);
+    await expect(page.getByTestId("grid")).toBeVisible();
+
+    // verify restart
+    await restart();
+    await page.reload();
+    await expect(page.getByTestId("fatal-error")).not.toBeVisible();
+    await expect(page.getByTestId("grid")).toBeVisible();
+    await page.getByTestId("grid").getByRole("button", { name: "edit" }).click();
+    await expectModalVisible(meterModal);
+    await expect(meterModal.getByLabel("Power")).toHaveValue("222");
+    await meterModal.getByRole("button", { name: "Close" }).click();
+    await expectModalHidden(meterModal);
+  });
+});
diff --git a/tests/config-invalid-template.sql b/tests/config-invalid-template.sql
new file mode 100644
index 000000000..9325272c8
--- /dev/null
+++ b/tests/config-invalid-template.sql
@@ -0,0 +1,21 @@
+BEGIN;
+
+CREATE TABLE `configs` (
+    `id` integer PRIMARY KEY AUTOINCREMENT
+  , `class` integer
+  , `type` text
+  , `title` text
+  , `icon` text
+  , `product` text
+  , `value` text
+);
+CREATE TABLE `settings` (
+    `key` text
+  , `value` text
+  , PRIMARY KEY(`key`)
+);
+
+INSERT INTO configs(id, class, type, title, icon, product, value) VALUES(1, 2, 'template', '', '', 'Demo meter', '{"maxacpower":"0","power_old":222,"template":"demo-meter","usage":"grid"}');
+INSERT INTO settings("key", value) VALUES('gridMeter', 'db:1');
+
+COMMIT;
\ No newline at end of file