diff --git a/mk2driver/mk2.go b/mk2driver/mk2.go
index e8b7da9..584b5af 100644
--- a/mk2driver/mk2.go
+++ b/mk2driver/mk2.go
@@ -346,7 +346,7 @@ func (m *mk2Ser) dcDecode(frame []byte) {
 	chargeC := m.applyScale(getUnsigned(frame[10:13]), ramVarIBat)
 	m.info.BatCurrent = usedC - chargeC
 
-	m.info.OutFrequency = 10 / (m.applyScale(float64(frame[13]), ramVarInverterPeriod))
+	m.info.OutFrequency = m.calcFreq(frame[13], ramVarInverterPeriod)
 	logrus.Debugf("dcDecode %#v", m.info)
 
 	// Send L1 status request
@@ -362,12 +362,8 @@ func (m *mk2Ser) acDecode(frame []byte) {
 	m.info.InCurrent = m.applyScale(getSigned(frame[7:9]), ramVarIMains)
 	m.info.OutVoltage = m.applyScale(getSigned(frame[9:11]), ramVarVInverter)
 	m.info.OutCurrent = m.applyScale(getSigned(frame[11:13]), ramVarIInverter)
+	m.info.InFrequency = m.calcFreq(frame[13], ramVarMainPeriod)
 
-	if frame[13] == 0xff {
-		m.info.InFrequency = 0
-	} else {
-		m.info.InFrequency = 10 / (m.applyScale(float64(frame[13]), ramVarMainPeriod))
-	}
 	logrus.Debugf("acDecode %#v", m.info)
 
 	// Send status request
@@ -376,6 +372,13 @@ func (m *mk2Ser) acDecode(frame []byte) {
 	m.sendCommand(cmd)
 }
 
+func (m *mk2Ser) calcFreq(data byte, scaleIndex int) float64 {
+	if data == 0xff || data == 0x00 {
+		return 0
+	}
+	return 10 / (m.applyScale(float64(data), scaleIndex))
+}
+
 // Decode charge state of battery.
 func (m *mk2Ser) stateDecode(frame []byte) {
 	m.info.ChargeState = m.applyScaleAndSign(frame[1:3], ramVarChargeState)
diff --git a/mk2driver/mk2_test.go b/mk2driver/mk2_test.go
index f96a7e8..359ba2a 100644
--- a/mk2driver/mk2_test.go
+++ b/mk2driver/mk2_test.go
@@ -249,3 +249,63 @@ func Test_mk2Ser_scaleDecode(t *testing.T) {
 		})
 	}
 }
+
+func Test_mk2Ser_calcFreq(t *testing.T) {
+	tests := []struct {
+		name       string
+		scales     []scaling
+		data       byte
+		scaleIndex int
+		want       float64
+	}{
+		{
+			name: "Calculate working low",
+			scales: []scaling{
+				{supported: false},
+			},
+			data:       0x01,
+			scaleIndex: 0,
+			want:       10,
+		},
+		{
+			name: "Calculate working high",
+			scales: []scaling{
+				{
+					supported: true,
+					offset:    0,
+					scale:     0.01,
+				},
+			},
+			data:       0xFE,
+			scaleIndex: 0,
+			want:       3.937007874015748,
+		},
+		{
+			name: "Calculate clip high",
+			scales: []scaling{
+				{supported: false},
+			},
+			data:       0xff,
+			scaleIndex: 0,
+			want:       0,
+		},
+		{
+			name: "Calculate clip low",
+			scales: []scaling{
+				{supported: false},
+			},
+			data:       0x00,
+			scaleIndex: 0,
+			want:       0,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			m := &mk2Ser{
+				scales: tt.scales,
+			}
+			got := m.calcFreq(tt.data, tt.scaleIndex)
+			assert.InDelta(t, tt.want, got, testDelta)
+		})
+	}
+}