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How to monitor 240v ac (US) power use? (lemmy.world)
submitted 1 week ago by to c/homeassistant@lemmy.world
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Can anyone point to resources, reviews or experiences on monitoring power usage in 240v ac (US)?

Looking at the new energy dashboard features …. I have opower integration of my electricity usage and a nice graph. However most of my power usage is from a heat pump, and EV charger, and maybe a garage heater. All are 240v, larger current loads. So the new feature is something about graphing device usage with overall usage. So that would be cool to add

I started searching online and it doesn’t seem especially positive. I see a few clamp meters with integrations but also see reviews that they’re not very accurate.

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[–] 2 points 1 week ago* (3 children)

https://a.co/d/0gDkYwiB

I have this thing, if you didn't find it in your searching. It seems accurate enough to me, but I'm not sure how I (or any other reviewers) would test that for certain. Guess I could turn off all but one circuit and put a kill a watt on a microwave or something. Whenever I've checked the graphs the readings make sense to me based on what was running at the time.

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  • [–] [S] 2 points 1 week ago (2 children)

    Maybe accuracy is not the right word: I see your point that it’s likely accurate enough. My concern was consistency.

    The total power usage as reported by my utility is measured one way and these measure a different way. Any error compounds, and the goal is to graph them against each other. Is it enough to make an impact?

    That specific product has two sensors. That means only one 240v circuit, right?

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  • [–] 2 points 1 week ago* (1 child)

    Ahh, yeah, I guess I haven't compared it to my actual bill yet. I should do that. Have to wait a few more months for data to pile up as I just moved in. I will say, I don't understand why it matters if it perfectly matches the utility company, what are you exactly trying to do?

    And yeah, two sensors. I put it on the lines into my house as my main concern was going over 100a in the whole house, as my old house doesn't have a main breaker. I do see now that you wanted to do a device-by-device breakout so that would require buying a fair few of these, and there's gotta be a cheaper way.

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  • [–] [S] 1 point 1 week ago

    I saw reviews where the clamps measured as much as 40% high. If my heat pump is 75% of my usage and it read that high, then when I look as a percentage of total use, it will be over 100% and my “untracked” usage will be invisible

    I agree it’s expensive, but the emporia one someone else mentioned has more meters on one device. I do have smart switches which directly measure power consumption so lights are covered. I know there are outlets so I could probably cover things like a freezer if I wanted to. But there’s really only a handful of devices which use noticeable power

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