Sensitive smart plug?

iamgigglz · 2025-09-17T15:48:15+0100

I'm using a smart plug to monitor the power consumption of a dehumidifier. Based on the power draw I can tell what mode it's on etc. My problem is distinguishing between standby and Off, because standy only uses around 0.5W. My current plug (Meross MSS315) often reports 0.0W, I think when power draw is under 0.5W.

Are there any HA-friendly smart plugs out there that'll give me a more accurate reading at very low wattages? I don't actually need the switching capability; just power draw.
Thanks

jpaul · 2025-09-17T20:28:28+0100

Are the kwh reported ie. integrated power. not accurate, even if the power draw is beneath the precision it can report.
.. so the coulomb counting works.

leezer3 · 2025-09-17T21:38:48+0100

You aren't going to get that level of accuracy reliably unfortunately.
Anything under ~10w or so is close to guesswork, and the accuracy of these things varies wildly.

https://www.sciencedirect.com/science/article/pii/S2772671123000323

iamgigglz · 2025-09-18T09:03:18+0100

Yeah I thought as much. I'm actually not too bothered about accuracy at low wattages;it's more about distinguishing between zero and non-zero.

iamgigglz · 2025-09-18T09:03:57+0100

jpaul said:
Are the kwh reported ie. integrated power. not accurate, even if the power draw is beneath the precision it can report.
.. so the coulomb counting works.

Good point! I'll have a look.