I have an odd situation where I live on a floor split in two and I want to split the electricity bill fairly with my floormate. I am looking at the home energy monitoring systems that have all the little ampmeters that go around the hot wires in the panel.

The problem is that we use split system A/C, there is only one A/C compressor for the floor and the power for the indoor units comes back from the compressor.

I'm thinking I can use the hot wires coming from the compressor instead of the circuit going from the panel to the compressor to figure out relative usage. (Won't measure the amperage used by the compressor, but will know relative amperages of the individual indoor units.)

Am I on the right track? Will I have to run the return power wires adjacent to the panel for proximity purposes? Are there systems with wireless meters? This Emporia system on Amazon looks like it has two large ampmeters around the main wires and then smaller ampmeters for each circuit - does this system require the sum of the smaller ampmeters to equal the current of the large ampmeters? Because if I set it up like above, I won't put an ampmeter on the one circuit that goes to the compressor, and then the sum of the little ampmeters won't be the same as the total amps.

Kinda lost here, would love to figure out a good hack.


  • 3
    Take the monthly bill, divide in half. Talk to the landlord about splitting the panel & metering so each flat/apartment gets its own bill. Since this is a rental, adding things to the panel may not be legal anyway.
    – FreeMan
    Apr 4, 2022 at 14:38
  • 5
    Unless there is a large difference of power usage between the two of you, the difference in bills might not pay for monitors.
    – crip659
    Apr 4, 2022 at 15:11
  • 2
    @FreeMan or if there's a significant difference in square footage, divide proportionally.
    – LShaver
    Apr 4, 2022 at 15:37

1 Answer 1


To add to @crip659 and @LSHaver's comments, unless there's a huge difference in other electronics connected, that A/C is probably your biggest electricity consumer, so dividing by floor space (which translates to the air conditioned volume per apartment) is probably the quickest and most cost effective way of dividing up said energy bill.

If you want to add some data to this, you could measure said A/C's electricity consumption for a while during its active season, by hooking it up to a simple plug in energy monitor (make sure it can cover the required wattage though as these things can potentially draw kilowatts), and compare that data to the energy bill.

The difference is everything else (lighting, TVs, laptops and whatnot), and depending on the local climate, probably a fraction of that, showing more detailed measuring would take more effort and money than warranted. You can even leave it hanging and do a final calculation after a year if you want.

These things are fairly cheap and easy to use, a quick google search shows one that measures up to 1650W for ~$30.

  • Hi, thanks for your comment. The compressor is on a 50 amp hard wired circuit, a plug in energy monitor won't work. Apr 11, 2022 at 3:08
  • Sorry to hear, must be a code difference between countries then. Everything in my apartment has a plug that can be removed, even equipment that draws significant power. Measuring won't be impossible by the way, just a bit more complicated.
    – MiG
    Apr 11, 2022 at 17:26

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