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?
Edit: thanks everyone for chiming in! To clarify a few things:
- I wasn’t (at least initially) looking for a permanent installation on my home server, but rather a good instrument to measure things around the house once I’m done fiddling with the server.
- the comparison with Fluke was just to illustrate what kind of error we can expect from a Kill-a-watt. It would be nice to have a Fluke power meter, but there’s nothing I do at home would even come close to justify it. The kill-a-watt is such an old design and the company behind it seems to focus on cheap trinkets. I was just hoping to find something a bit better than what P3 offers. Wouldn’t mind paying up to $75 for the same features and better accuracy.
- I looked for a multimeter that measured power somehow as I need a better one that can measure capacitance too anyway. Didn’t find it.
If there is a problem at low power usage then you can easily solve it by temporary add more power. Lets say add a 40watt lamp or something, later remove it from the calculation.
While it sounds a bit hacky, I think this is an underrated solution. It’s actually quite a clever way to bypass the whole problem. Physics is your enemy here, not economics.
This is kind of like trying to find an electric motor with the highest efficiency and torque at 1 RPM. While it’s not theoretically impossible, it’s not just a matter of price or design, it’s a matter of asking the equipment to do something it’s simply not good at, while you want to do it really well. It can’t, certainly not affordably or without significant compromises in other areas. In the case of a motor, you’d be better off letting the motor spin at its much higher optimal RPM and gear it down, even though there will be a little loss in the geartrain it’s still a much better solution overall and that’s why essentially every low speed motor is designed this way.
In the case of an ammeter, it seems totally reasonable to bring it up to a more ideal operating range by adding a constant artificial load. In fact the high precision/low range multimeters and oscilloscopes are usually internally doing almost exactly the same thing with their probes, just in a somewhat more complex way behind the scenes.