What determines devices that support Power measurement?

I wish to pull a list of only devices that are actively reflecting a power measurement (wattage).
All I can get so far is all outlets but I just want to list ones with wattage.
I've tried voltageMeasurement and powerMeter. EnergyMeter?

Never mind. case sensitivity issue - I had VoltageMeasurement not voltageMeasurement. crappy programming language!

@moderators please close. Thanks.