diff --git a/hems/config.go b/hems/config.go
index f97e7ceaf..89119487c 100644
--- a/hems/config.go
+++ b/hems/config.go
@@ -19,7 +19,7 @@ func NewFromConfig(ctx context.Context, typ string, other map[string]any, site s
 		return nil, errors.New("breaking change: Sunny Home Manager integration is always on. See https://github.com/evcc-io/evcc/releases and https://docs.evcc.io/en/docs/integrations/sma-sunny-home-manager")
 	case "eebus":
 		return eebus.NewFromConfig(ctx, other, site)
-	case "fnn-3":
+	case "fnn", "fnn-3":
 		return fnn.NewFromConfig(ctx, other, site)
 	case "relay":
 		return relay.NewFromConfig(ctx, other, site)
diff --git a/hems/fnn/fnn-3.go b/hems/fnn/fnn-3.go
deleted file mode 100644
index d78d92e3f..000000000
--- a/hems/fnn/fnn-3.go
+++ /dev/null
@@ -1,153 +0,0 @@
-package fnn
-
-import (
-	"context"
-	"sync"
-	"time"
-
-	"github.com/evcc-io/evcc/api"
-	"github.com/evcc-io/evcc/core/site"
-	"github.com/evcc-io/evcc/hems/smartgrid"
-	"github.com/evcc-io/evcc/plugin"
-	"github.com/evcc-io/evcc/util"
-)
-
-type Fnn3 struct {
-	mu  sync.Mutex
-	log *util.Logger
-
-	root       api.Circuit
-	s1, s2, w3 func() (bool, error)
-
-	smartgridID uint
-	limit       *float64
-	maxPower    float64
-	interval    time.Duration
-}
-
-// NewFromConfig creates an Fnn3 HEMS from generic config
-func NewFromConfig(ctx context.Context, other map[string]any, site site.API) (*Fnn3, error) {
-	cc := struct {
-		MaxPower float64
-		W3       plugin.Config
-		S1       *plugin.Config
-		S2       *plugin.Config
-		Interval time.Duration
-	}{
-		Interval: 10 * time.Second,
-	}
-
-	if err := util.DecodeOther(other, &cc); err != nil {
-		return nil, err
-	}
-
-	// setup grid control circuit
-	gridcontrol, err := smartgrid.SetupCircuit()
-	if err != nil {
-		return nil, err
-	}
-
-	site.SetCircuit(gridcontrol)
-
-	// s1 getter
-	s1G, err := cc.S1.BoolGetter(ctx)
-	if err != nil {
-		return nil, err
-	}
-
-	s2G, err := cc.S2.BoolGetter(ctx)
-	if err != nil {
-		return nil, err
-	}
-
-	w3G, err := cc.W3.BoolGetter(ctx)
-	if err != nil {
-		return nil, err
-	}
-
-	return NewFnn3(gridcontrol, s1G, s2G, w3G, cc.MaxPower, cc.Interval)
-}
-
-// NewFnn3 creates Fnn3 HEMS
-func NewFnn3(root api.Circuit, s1, s2, w3 func() (bool, error), maxPower float64, interval time.Duration) (*Fnn3, error) {
-	c := &Fnn3{
-		log:      util.NewLogger("fnn3"),
-		root:     root,
-		maxPower: maxPower,
-		s1:       s1,
-		s2:       s2,
-		w3:       w3,
-		interval: interval,
-	}
-
-	return c, nil
-}
-
-func (c *Fnn3) Run() {
-	for range time.Tick(c.interval) {
-		if err := c.run(); err != nil {
-			c.log.ERROR.Println(err)
-		}
-	}
-}
-
-func (c *Fnn3) run() error {
-	w3, err := c.w3()
-	if err != nil {
-		return err
-	}
-
-	if w3 {
-		// 0%
-		return c.curtail(0.0)
-	}
-
-	if c.s2 != nil {
-		s2, err := c.s2()
-		if err != nil {
-			return err
-		}
-
-		if s2 {
-			// 30%
-			return c.curtail(0.3)
-		}
-	}
-
-	if c.s1 != nil {
-		s1, err := c.s1()
-		if err != nil {
-			return err
-		}
-
-		if s1 {
-			// 60%
-			return c.curtail(0.6)
-		}
-	}
-
-	// 100%
-	return c.curtail(1.0)
-}
-
-func (c *Fnn3) curtail(frac float64) error {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	active := frac < 1.0
-
-	c.limit = nil
-	if active {
-		c.limit = new(c.maxPower * frac)
-	}
-
-	c.root.Curtail(active)
-	// TODO make ProductionNominalMax configurable (Site kWp)
-	// c.root.SetMaxPower(c.maxPower*frac)
-
-	if err := smartgrid.UpdateSession(&c.smartgridID, smartgrid.Curtail, c.root.GetChargePower(), c.maxPower*frac, active); err != nil {
-		c.log.ERROR.Printf("smartgrid session: %v", err)
-	}
-
-	return nil
-}
diff --git a/hems/fnn/fnn.go b/hems/fnn/fnn.go
new file mode 100644
index 000000000..6d3d6c341
--- /dev/null
+++ b/hems/fnn/fnn.go
@@ -0,0 +1,231 @@
+package fnn
+
+import (
+	"context"
+	"errors"
+	"math"
+	"sync"
+	"time"
+
+	"github.com/evcc-io/evcc/api"
+	"github.com/evcc-io/evcc/core/site"
+	"github.com/evcc-io/evcc/hems/smartgrid"
+	"github.com/evcc-io/evcc/plugin"
+	"github.com/evcc-io/evcc/util"
+)
+
+// NewFromConfig creates an FNN HEMS from generic config.
+func NewFromConfig(ctx context.Context, other map[string]any, site site.API) (*Fnn, error) {
+	cc := struct {
+		MaxPower        float64 // TODO deprecated
+		MaxDimPower     float64
+		MaxCurtailPower *float64
+		W3              *plugin.Config
+		S1              *plugin.Config
+		S2              *plugin.Config
+		W4              *plugin.Config
+		Interval        time.Duration
+	}{
+		Interval: 10 * time.Second,
+	}
+
+	if err := util.DecodeOther(other, &cc); err != nil {
+		return nil, err
+	}
+
+	// setup grid control circuit
+	gridcontrol, err := smartgrid.SetupCircuit()
+	if err != nil {
+		return nil, err
+	}
+
+	site.SetCircuit(gridcontrol)
+
+	w3G, err := cc.W3.BoolGetter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	w4G, err := cc.W4.BoolGetter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	// either dim or curtail must be configured
+	if w3G == nil && w4G == nil {
+		return nil, errors.New("must have either W3 or W4")
+	}
+
+	s1G, err := cc.S1.BoolGetter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	s2G, err := cc.S2.BoolGetter(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	maxDimPower := math.Abs(cc.MaxDimPower)
+
+	var maxCurtailPower *float64
+	switch {
+	case cc.MaxCurtailPower != nil:
+		maxCurtailPower = new(math.Abs(*cc.MaxCurtailPower))
+	case cc.MaxPower > 0:
+		// fnn-3 backwards compatibility: legacy MaxPower was the PV/curtail cap
+		maxCurtailPower = new(math.Abs(cc.MaxPower))
+	}
+
+	return &Fnn{
+		log:             util.NewLogger("fnn"),
+		root:            gridcontrol,
+		maxDimPower:     maxDimPower,
+		maxCurtailPower: maxCurtailPower,
+		s1:              s1G,
+		s2:              s2G,
+		w3:              w3G,
+		w4:              w4G,
+		interval:        cc.Interval,
+	}, nil
+}
+
+// Fnn implements the FNN HEMS logic for curtailment and dimming.
+type Fnn struct {
+	mu  sync.Mutex
+	log *util.Logger
+
+	root       api.Circuit
+	s1, s2, w3 func() (bool, error)
+	w4         func() (bool, error)
+
+	smartgridConsumptionID uint
+	smartgridProductionID  uint
+
+	maxDimPower     float64
+	maxCurtailPower *float64
+	interval        time.Duration
+}
+
+// Run starts the FNN control loop.
+func (c *Fnn) Run() {
+	ticker := time.NewTicker(c.interval)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		if err := c.runCurtail(); err != nil {
+			c.log.ERROR.Println(err)
+		}
+
+		if err := c.runDim(); err != nil {
+			c.log.ERROR.Println(err)
+		}
+	}
+}
+
+// runCurtail evaluates curtailment rules and applies the appropriate limit.
+// No-op if no curtail input is configured.
+func (c *Fnn) runCurtail() error {
+	if c.w3 == nil {
+		return nil
+	}
+
+	rules := []struct {
+		get  func() (bool, error)
+		frac float64
+	}{
+		{get: c.w3, frac: 0.0},
+		{get: c.s2, frac: 0.3},
+		{get: c.s1, frac: 0.6},
+	}
+
+	for _, rule := range rules {
+		if rule.get == nil {
+			continue
+		}
+
+		active, err := rule.get()
+		if err != nil {
+			return err
+		}
+
+		if active {
+			return c.setProductionLimit(rule.frac)
+		}
+	}
+
+	// 100%
+	return c.setProductionLimit(1.0)
+}
+
+// runDim evaluates the dimming rule and applies the dim limit.
+// No-op if dim input is not configured.
+func (c *Fnn) runDim() error {
+	if c.w4 == nil {
+		return nil
+	}
+
+	active, err := c.w4()
+	if err != nil {
+		return err
+	}
+
+	limit := 0.0
+	if active {
+		if c.maxDimPower <= 0 {
+			return errors.New("dim active but no limit configured")
+		}
+
+		limit = c.maxDimPower
+	}
+
+	return c.setConsumptionLimit(limit)
+}
+
+func (c *Fnn) applyMode(id *uint, typ smartgrid.Type, active bool, limit float64, applyRoot func()) {
+	applyRoot()
+
+	if err := smartgrid.UpdateSession(id, typ, c.root.GetChargePower(), limit, active); err != nil {
+		c.log.ERROR.Printf("smartgrid session: %v", err)
+	}
+}
+
+// setProductionLimit applies the curtailment limit to the circuit.
+func (c *Fnn) setProductionLimit(frac float64) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	limit := 0.0
+	active := frac < 1.0
+
+	if active {
+		if c.maxCurtailPower == nil {
+			return errors.New("curtail active but no limit configured")
+		}
+
+		limit = *c.maxCurtailPower * frac
+	}
+
+	c.applyMode(&c.smartgridProductionID, smartgrid.Curtail, active, limit, func() {
+		c.root.Curtail(active)
+		// TODO make ProductionNominalMax configurable (Site kWp)
+		// c.root.SetMaxPower(c.maxPower*frac)
+	})
+
+	return nil
+}
+
+// setConsumptionLimit applies the dimming limit to the circuit.
+func (c *Fnn) setConsumptionLimit(limit float64) error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	active := limit > 0
+
+	c.applyMode(&c.smartgridConsumptionID, smartgrid.Dim, active, limit, func() {
+		c.root.Dim(active)
+		c.root.SetMaxPower(limit)
+	})
+
+	return nil
+}