diff --git a/core/site_circuits.go b/core/site_circuits.go
index 6aceb79fe..5e97c2f91 100644
--- a/core/site_circuits.go
+++ b/core/site_circuits.go
@@ -73,14 +73,13 @@ func (site *Site) dimMeters(dim bool) error {
 			continue
 		}
 
-		if dimmed, err := backoff.RetryWithData(m.Dimmed, modbus.Backoff()); err == nil {
-			if dim == dimmed {
-				continue
-			}
-		} else {
-			if !errors.Is(err, api.ErrNotAvailable) {
-				errs = errors.Join(errs, fmt.Errorf("%s dimmed: %w", deviceTitleOrName(dev), err))
-			}
+		// unreadable state: apply unconditionally
+		dimmed, err := backoff.RetryWithData(m.Dimmed, modbus.Backoff())
+		if err != nil && !errors.Is(err, api.ErrNotAvailable) {
+			errs = errors.Join(errs, fmt.Errorf("%s dimmed: %w", deviceTitleOrName(dev), err))
+			continue
+		}
+		if err == nil && dim == dimmed {
 			continue
 		}
 
@@ -115,14 +114,13 @@ func (site *Site) curtailPV(percent *int) error {
 			continue
 		}
 
-		if curtailed, err := backoff.RetryWithData(m.CurtailedPercent, modbus.Backoff()); err == nil {
-			if curtailed == *percent {
-				continue
-			}
-		} else {
-			if !errors.Is(err, api.ErrNotAvailable) {
-				errs = errors.Join(errs, fmt.Errorf("%s curtailed: %w", deviceTitleOrName(dev), err))
-			}
+		// unreadable state: apply unconditionally
+		curtailed, err := backoff.RetryWithData(m.CurtailedPercent, modbus.Backoff())
+		if err != nil && !errors.Is(err, api.ErrNotAvailable) {
+			errs = errors.Join(errs, fmt.Errorf("%s curtailed: %w", deviceTitleOrName(dev), err))
+			continue
+		}
+		if err == nil && curtailed == *percent {
 			continue
 		}
 
diff --git a/core/site_circuits_test.go b/core/site_circuits_test.go
index 7e7e26e60..e18aa53c9 100644
--- a/core/site_circuits_test.go
+++ b/core/site_circuits_test.go
@@ -15,19 +15,18 @@ import (
 type curtailableMeter struct {
 	api.Meter
 	percent  int
+	getErr   error
 	setErr   error
 	gets     int
-	sets     int
 	setCalls []int
 }
 
 func (m *curtailableMeter) CurtailedPercent() (int, error) {
 	m.gets++
-	return m.percent, nil
+	return m.percent, m.getErr
 }
 
 func (m *curtailableMeter) SetCurtailPercent(percent int) error {
-	m.sets++
 	m.setCalls = append(m.setCalls, percent)
 	if m.setErr != nil {
 		return m.setErr
@@ -93,10 +92,26 @@ func TestCurtailPVNoStatement(t *testing.T) {
 	assert.Equal(t, []int{60}, m.setCalls)
 }
 
+// A device that cannot report its state is written once, not on every cycle.
+func TestCurtailPVNotAvailable(t *testing.T) {
+	m := &curtailableMeter{getErr: api.ErrNotAvailable}
+	site := curtailSite(m)
+
+	for range 3 {
+		require.NoError(t, site.curtailPV(new(60)))
+	}
+	assert.Equal(t, []int{60}, m.setCalls)
+
+	// changed: applied again
+	require.NoError(t, site.curtailPV(new(30)))
+	assert.Equal(t, []int{60, 30}, m.setCalls)
+}
+
 // dimmableMeter counts device interactions to verify caching.
 type dimmableMeter struct {
 	api.Meter
 	dimmed   bool
+	getErr   error
 	dimErr   error
 	gets     int
 	dimCalls []bool
@@ -104,7 +119,7 @@ type dimmableMeter struct {
 
 func (m *dimmableMeter) Dimmed() (bool, error) {
 	m.gets++
-	return m.dimmed, nil
+	return m.dimmed, m.getErr
 }
 
 func (m *dimmableMeter) Dim(dim bool) error {
@@ -116,12 +131,16 @@ func (m *dimmableMeter) Dim(dim bool) error {
 	return nil
 }
 
+func dimSite(m api.Meter) *Site {
+	return &Site{
+		log:       util.NewLogger("foo"),
+		auxMeters: []config.Device[api.Meter]{config.NewStaticDevice(config.Named{}, m)},
+	}
+}
+
 func TestDimMetersCache(t *testing.T) {
 	m := &dimmableMeter{}
-	site := &Site{
-		log:       util.NewLogger("foo"),
-		auxMeters: []config.Device[api.Meter]{config.NewStaticDevice(config.Named{}, api.Meter(m))},
-	}
+	site := dimSite(m)
 
 	require.NoError(t, site.dimMeters(true))
 	assert.Equal(t, []bool{true}, m.dimCalls)
@@ -142,3 +161,17 @@ func TestDimMetersCache(t *testing.T) {
 	require.Error(t, site.dimMeters(true))
 	assert.Equal(t, []bool{true, false, true, true}, m.dimCalls)
 }
+
+// A device that cannot report its state is written once, not on every cycle.
+func TestDimMetersNotAvailable(t *testing.T) {
+	m := &dimmableMeter{getErr: api.ErrNotAvailable}
+	site := dimSite(m)
+
+	for range 3 {
+		require.NoError(t, site.dimMeters(true))
+	}
+	assert.Equal(t, []bool{true}, m.dimCalls)
+
+	require.NoError(t, site.dimMeters(false))
+	assert.Equal(t, []bool{true, false}, m.dimCalls)
+}