I'm considering buying something like this for my primary sump pump. But they sell it in a 2000w and a 1500w configuration. I have no easy way to figure out my sump pump's horsepower since it came in the house, but I used a voltage tester thing and it pulls about 500 watts. Does that mean I'd be fine to buy the 1500w? Does it make sense to future proof and get the 2000w? My plan is only to plug in the main sump pump, I won't really use it for powering up any other devices.

Sorry if this is a dumb question haha :)

  • Assuming it's anything like a typical motor efficiency, if it draws 500W running, (which would be 2/3 HP with a 100% efficient motor that doesn't exist) it's either 1/2 HP or an unusually inefficient 1/3 HP motor. Note that any suitable power pure sine wave UPS will do the same job with the same battery capacity. Slapping a "sump-pump" label on it doesn't change what it is or does. Don't use a MSW (modified sine wave, which is more accurately a crude square wave) inverter to run motors.
    – Ecnerwal
    Commented Oct 6, 2023 at 14:04
  • Just a side note: You might also want to investigate venturi backup pumps. These are powered by water pressure, and so make backing up the electricity to run the pump the municipality's problem rather than yours. Less efficient but runs as long as water is being provided rather than only as long as your battery holds out. I've meaning to install one myself.
    – keshlam
    Commented Oct 6, 2023 at 20:42
  • Thank you for the info! Sounds to me like 1500 would be more than enough for pretty much any reasonable sump pump then Commented Oct 6, 2023 at 21:07
  • @Ecnerwal do you have any suggestions for other UPS's that might work just as well that are cheaper? Commented Oct 6, 2023 at 21:14
  • That would be a shopping question and those are off-topic. If you can manage the proper keywords, you can shop for yourself. I tend to think that a vendor that markets their pure sine wave UPS as being "somehow particularly special to sump pumps" may be overcharging, so shopping around would be a good plan. Particularly with all the solar-related stuff now available. But beware the MSW (which are universally cheaper, because the electronics are crude by comparison.) And if you expect a reasonable runtime for a 500W pump +inverter losses (not 100% efficient), realize that takes a BIG battery.
    – Ecnerwal
    Commented Oct 6, 2023 at 21:24

1 Answer 1


If it's drawing 500W, then yes, you'll be fine with a 1500W power supply.

  • 1
    If shopping around, (rather than picking between two that are both large enough) probably want at least 1000W to start the thing, though.
    – Ecnerwal
    Commented Oct 6, 2023 at 14:09
  • Thank you so much! That'll save me a couple hundred bucks :) Commented Oct 6, 2023 at 21:05

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