I want to measure the power coming out of a 120V outlet that can go up to 20 Amps. A standard household circuit is limited to 15 amps but this is a special situation where we're running our own temporary power grid off a generator. Specifically, the plugs are "NEMA 5-20P" where one of the blades can be slanted.

All the watt-meters I find online only support up to 1800W/15A since they're meant for home use. Usually, that'll be fine, but situations where we start drawing more than 15 amps is exactly when I want to know how much I'm using.

Any ideas on to build something that can measure current/power when it can go up to 20A? At this point off the shelf doesn't seem like an option so I figure I'll make to make my own and would love some tips.


  • Unfortunately, "shopping" questions are off-topic here. Please take our tour so you'll know how best to participate here. – Daniel Griscom Aug 9 '19 at 1:57
  • 2
    Can you get your paws on a clampmeter and plug adapter for same? – ThreePhaseEel Aug 9 '19 at 2:21
  • @DanielGriscom thanks! At this point, I figure I'll have to make my own meter, so I tweaked the question to reflect that and make it less about "shopping" =) – Chris Aug 9 '19 at 2:22
  • 1
    This is a dupe of diy.stackexchange.com/questions/131012/diy-ac-line-splitter, basically (can't VtC it any longer) – ThreePhaseEel Aug 9 '19 at 2:34
  • 1
    if you get a current transformer to make your own. be warned ... these devices are EXTREMELY dangerous. they can have DEADLY voltages. if you don't thoroughly understand how they work and are wired, don't mess with them. – Skaperen Aug 9 '19 at 3:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.