Power Meter Accuracy

I recently purchased 4 power meter plugs of 3 different types (one came in a 2 pack). Accuracy vs non-smart power meter is pretty bad.

  1. Aeotec Smart Switch 6, Zwave Switch Z-Wave Plus Plug 15A for Home Security Automation Z-Wave Power Monitor, Without USB Port

  2. Minoston Zooz Remote Switch Zen34, Z-Wave Plug with Energy Monitoring, Z-Wave Plus Mini Outlet Built-in Repeater Range Extender, Overcurrent Protection, Z-Wave Hub Required, Alexa and Google Assistant Compatible(MP21ZP)

  3. NEO Z-Wave Plus Smart Mini Power Plug Zwave Socket Zwave Outlet With Timing and Energy Monitoring Home Automation, Work with Wink, SmartThings, Vera, Fibaro & more, Green&Blue 2PK

I tested these against a non-smart power meter: kuman KW47-US Electricity Usage Monitor Plug Power Watt Voltage Amps Meter with Digital LCD, Overload Protection and 7 Display Modes for Energy Saving (NO-Backlight), white

  1. Aeotec: matched the power meter well
  2. Minoston: over-reported by 10-15W
  3. Neo: One of the two matched the Kuman, but the other under-reported by 20W. Both have the same config/params on hubitat.

Is there something I could be doing wrong, or is it the smart devices?

Without knowing any of those but having some kind of background in instrumentation, none of those are sold to be a precise measuring device. This seems to be the case also for the non-smart one. You mentioned an error of 15-20 W, but what was the reading?

A error up to 5% (although is a lot) is I believe normal those devices that are not specifically sold for measurement since no calibration certificate are sold with them.

But if you have a precise measuring power meter you could have a custom driver an then calibrate the reading for your specific device.


Watts is inherently erroneous. Amps is a better measurement, if it is available. Issue is what the system uses for raw data, amps/volts or watts/volts and then how they calculate the other parameter.