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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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[–] 8 points 1 week ago (7 children)

I have a couple emporia vue (2's) and for my electric clothes dryer I just use a CT clamp on each leg and sum them.

Within the vue esphome config:

 # Combined Dryer Sensor
  - platform: template
    name: "Total Clothes Dryer Power"
    id: total_dryer_power
    lambda: return id(cir9).state + id(cir12).state;
    update_interval: never
    device_class: power
    state_class: measurement
    unit_of_measurement: "W"
    filters: *throttle_avg
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  • [–] [S] 0 points 1 week ago* (last edited 1 week ago) (6 children)

    Do you need to cut the outer insulation off? How else do you get to both legs?

    Edit: I see, it mounts in the panel. Actually brings up a different challenge since my electrical has evolved over the years into multiple sub panels

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  • [–] 3 points 1 week ago*

    The CT clamp reads the current without having to be directly connected to the wire. It just 'clamps' onto the leg and is non invasive. https://en.wikipedia.org/wiki/Current_clamp

    Here's one of my panels with the clamps on. The top clamps read total power, the individual clamps below are reading one leg each. for a 240v you need both since each leg is only supplying 120. My dryer also sometimes only uses 120v when it's not actively heating.

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  • [–] 1 point 1 week ago (4 children)

    I have two 150a panels in my house and I have 2 emporia vue 2's one on each panel. I reflashed them with esphome so I own the data, it's not going out to emporia. but they work as individual devices collecting data from the clamps.

    For non 240 loads you could also use smart plug with power consumption if you're just wanting to track that device. In my use case I am capturing all usage from the two big clamp at the top of each panel then each clamps usage which gives me an 'untracked' value also since I have more than 16 circuits in each panel I cannot track every circuit.

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  • [–] [S] 1 point 6 days ago (3 children)

    That’s an interesting idea - is there a guide for newbies? I’ve never done anything with esphome.

    I had been expecting to use the total power from my utility but perhaps that’s a better idea: measure total power with the same tool as individual.

    Right, a big part of the goal is to identify whether untracked is significant.

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  • [–] 2 points 6 days ago

    It's been a little while but I did follow a guide for the emporia vue.

    There are newer versions and other similar brands out there if I find the guide I used it will be fairly specific to this hardware (certainly the base code setup)

    I will look tomorrow

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