XTension supports all power metering devices that the Vera supports. For modules or switches that support power metering XTension will automatically create separate units to support all the information that the units can send. For the standard appliance module with power monitoring you’ll get 3 units in XTension. The first will be for controlling the on/off status of the unit itself. The second will be the current live power usage in watts. The last will be a unit to hold the cumulative KWH usage that the device has measured since you plugged it in.
As of version 9.1 you can reset the KWH measurements in the device itself by just turning off the KWH unit in question. The OFF sent to the interface will send the command to clear the KWH counter and reset it back to 0. Perhaps you want to accumulate the monthly power usage for your fridge or some other device, this is now simpler than trying to save off the previous value and subtracting it to get the current total.
Not all KWH measuring devices support the command to clear their counter however. Depending on the device you may get an error instead of having the value return to 0.
If you’re trying to reset a device that was created in XTension prior to version 9.1 then you will first have to edit the unit in XTension and turn off the “Receive Only” checkbox so that it will actually send the off command. Prior to 9.1 these units were marked as receive only.