So I wanted to get myself a Kill-a-watt. Being who I am, I wanted information regarding its accuracy, especially at low power draws. I found a comparison with a industry grade equipment (Fluke is about the best out there in handheld electrical meters). It’s not encouraging, so I thought about a more proper meter, but it’s not easy to find an actual power meter that is accurate at low loads, isn’t a hassle to install and doesn’t cost an arm and a leg.
What do you use? Am I overthinking it?
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I personally make use of the sonoff pow smart plugs, with Tasmota firmware. Though any Tasmota compatible smart plug with power readings will work.
The key thing is that with Tasmota, you can properly calibrate the readings. I have a friend with a high quality power meter. I used that to calibrate my smart plugs, they seem to track within a few % of the expensive one, once calibrated.
Depending on if you have access to an expensive meter or not, this will either be the best bet, or completely useless to you. Your local Hackspace might also be a good option for getting your hands on an expensive meter for an evening.
I’ll look into it, sounds promising! Thanks!
Slight nitpick: Brymen handheld meters often have better specs in the handheld market, in particular when you are looking at a fixed price point.
You see a lot of Fluke meters around due to service agreement, as well as government and military contracts.
Don’t get me wrong, meters are fine, but there is no reason to spend that kinda money at home, unless the service manual of your washing machine explicitly states all measurements are to be done by a Fluke meter.
There was a youtube vid, testing multimeters, & there was a specific condition that produced wrong results in all the meters except Fluke, who had engineered to prevent that wrongness.
That was what decided me on trusting Fluke, in the future.
been years, no idea what channel it was on, sorry, but it should be findable for someone with patience, knowing that only the Fluke got it right, of the ones tested.
Do pay attention to the calibration-certificates, though:
Anybody paying for Fluke who ignores that their handhelds have no more than 2.5-digits of actual-accuracy, is foolish/incompetent.
( the cheap ones are sooo much worse… )
No way I’m spending over 2 grand to measure power. That was just a comparison to see how bad the killawatt is.
Are you looking to measure draw for one specific device or across circuits in your whole home. I’ve been considering two systems: IoTaWatt and Lantern Power Monitor. Both are open source and open hardware.
IoTaWatt uses entirely custom hardware for the actual device but serves its own webpage that can be accessed easily at home from any device and if you’re technically savvy can pass to other services. My reservation with it is if at some point in the future the hardware dies, how easy will it be to recreate if the main project goes dormant, even with the hardware open source? What if a chip manufacturer goes out of business or discontinues a part?
In contrast, the Lantern Power Monitor runs on Raspberry Pi with a relatively basic custom board you can solder yourself with minimal skill; I suspect you could even make it work with a breadboard. Recent shortages notwithstanding, Raspberry Pi seems to keep their models pretty available for a long time, so that inspires a little more confidence. On the flip side, the software primarily runs on a mobile app. There is an iPhone app but it doesn’t have as many features as the Android app. But what happens if the project is abandoned and the app is no longer updated to stay compatible with newer phones or operating systems? And the app by default sends the data to an outside server maintained by the main developer. He doesn’t charge for the hosting and it makes it easy to access from anywhere, but some people might have concerns about that. You can also configure it to self-host from the Raspberry Pi but then you need to have the know-how to make it accessible outside your home (if you want). Underneath it also relies on some other open source data analysis components and I assume if you really know what you’re doing you can pass it out to other software.
Of course, in the end I don’t have the budget to do either project right now.
One specific equipment at a time. Though I intend to delve into what you’re mentioning at some point.
I use Shelly Plus Plug S. Im not sure how accutate it is, but it does decent job for me. I feel like you are looking for something else, but wanted to mention shelly anyway
https://iotawatt.com/ is what I plan on using shortly
Tasmota nous sametplugs work great and have a tiny footprint. They integrate nicely in home assistant. They must be calibrated once with a resistive load eg old light bulb.
In terms of raw data, any properly calibrated equipment should be identical.
You could build one yourself or have a look at how to get readings from your actual electricity meter. Both can be found on the open energy monitor project page. If you self build i guess you could use a lower value CT that amplifies lower currents and just not use it at higher loads?
Mains power fluctuates a LOT though so youll definitely need averaging to some extent
Many residential tools can’t even be calibrated. Even if they are, calibration stability is a concern. The difference between a cheap instrument and a good one is short and long term repeatability.
Thanks for pointing open energy monitor, that seems overkill for what I need.
