Add watt to mysensors switch attributes (#13370)

homeassistant/components/switch/mysensors.py

@@ -72,6 +72,12 @@ class MySensorsSwitch(mysensors.MySensorsEntity, SwitchDevice):
         """Return True if unable to access real state of entity."""
         return self.gateway.optimistic
 
+    @property
+    def current_power_w(self):
+        """Return the current power usage in W."""
+        set_req = self.gateway.const.SetReq
+        return self._values.get(set_req.V_WATT)
+
     @property
     def is_on(self):
         """Return True if switch is on."""