Shelly: fix PM1 Gen3 energy readings (#31957)

meter/shelly.go

@@ -48,8 +48,13 @@ func NewShellyFromConfig(other map[string]any) (api.Meter, error) {
 	// Three-phase Shelly energy meters count each phase separately (non-balanced),
 	// making their totals unsuitable for bidirectional grid metering.
 	if !(c.usage == "grid" && c.conn.IsThreePhase()) {
-		implement.Has(c, implement.MeterEnergy(c.conn.TotalEnergy))
-		implement.Has(c, implement.MeterReturnEnergy(c.conn.ReturnEnergy))
+		total, ret := c.conn.TotalEnergy, c.conn.ReturnEnergy
+		if c.usage == "pv" {
+			// reverse direction
+			total, ret = ret, total
+		}
+		implement.Has(c, implement.MeterEnergy(total))
+		implement.Has(c, implement.MeterReturnEnergy(ret))
 	}
 
 	if phases, ok := c.conn.Generation.(shelly.Phases); ok {
@@ -83,8 +88,16 @@ func (c *Shelly) CurrentPower() (float64, error) {
 	if err != nil {
 		return 0, err
 	}
-	if c.usage == "pv" {
-		power = math.Abs(power)
-	}
-	return power, nil
+	return c.currentPowerForUsage(power, c.conn.SignedPower()), nil
+}
+
+// PV usage inverts directional power, otherwise the magnitude is used.
+func (c *Shelly) currentPowerForUsage(power float64, signed bool) float64 {
+	if c.usage != "pv" {
+		return power
+	}
+	if signed {
+		return -power
+	}
+	return math.Abs(power)
 }

meter/shelly/connection.go

@@ -30,6 +30,12 @@ type Phases interface {
 // Connection is the Shelly connection
 type Connection struct {
 	Generation
+	gen int
+}
+
+// SignedPower reports whether the device returns directional (signed) power.
+func (c *Connection) SignedPower() bool {
+	return c.gen >= 3
 }
 
 // NewConnection creates a new Shelly device connection.
@@ -79,7 +85,7 @@ func NewConnection(uri, user, password string, channel int, cache time.Duration)
 		}
 	}
 
-	conn := &Connection{gen}
+	conn := &Connection{Generation: gen, gen: resp.Gen}
 
 	return conn, nil
 }

meter/shelly/gen2.go

@@ -232,7 +232,10 @@ func (c *gen2) TotalEnergy() (float64, error) {
 
 	case c.hasSwitchEndpoint():
 		res, err := c.switchstatus.Get()
-		return res.Aenergy.Total / 1000, err
+		// https://shelly-api-docs.shelly.cloud/gen2/ComponentsAndServices/Switch#status
+		// NOTE: ret_aenergy - the active energy added to this container is also added to aenergy container.
+		// All the consumed energy is collected in aenergy regardless of the direction(consumed or returned) of the active energy.
+		return max(0, res.Aenergy.Total-res.Ret_Aenergy.Total) / 1000, err
 
 	default:
 		return 0, fmt.Errorf("unknown shelly model: %s", c.model)

meter/shelly/gen2_test.go

@@ -8,6 +8,12 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestSignedPower(t *testing.T) {
+	assert.False(t, (&Connection{gen: 1}).SignedPower())
+	assert.False(t, (&Connection{gen: 2}).SignedPower())
+	assert.True(t, (&Connection{gen: 3}).SignedPower())
+}
+
 // Test Gen2+ status responses
 func TestUnmarshalGen2StatusResponse(t *testing.T) {
 	{

meter/shelly_test.go

@@ -0,0 +1,30 @@
+package meter
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestShellyCurrentPowerForUsage(t *testing.T) {
+	tests := []struct {
+		name   string
+		usage  string
+		signed bool
+		power  float64
+		want   float64
+	}{
+		{name: "grid keeps sign", usage: "grid", power: -350, want: -350},
+		{name: "unsigned pv uses absolute value", usage: "pv", power: -350, want: 350},
+		{name: "unsigned pv keeps positive values", usage: "pv", power: 350, want: 350},
+		{name: "signed pv inverts positive values", usage: "pv", signed: true, power: 350, want: -350},
+		{name: "signed pv inverts negative values", usage: "pv", signed: true, power: -350, want: 350},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			m := &Shelly{usage: tc.usage}
+			assert.Equal(t, tc.want, m.currentPowerForUsage(tc.power, tc.signed))
+		})
+	}
+}