I just bought a Prius Prime 2017 and wanted to see the consumption when charging. So I used my Kill-a-Watt to measure. I noticed that the Prius does not draw constant power. Sometimes it goes up to near 1,400 watts, which comes close to 12A in my 120V line and then goes down to 200W or so then up again for a few minutes. Since the Kill-a-Watt is rated 15A I thought it would be ok. About an hour after I initially connected it, I went to check and noticed my Kill-a-Watt display was blank. I thought maybe my circuit breaker tripped. But my breaker is 20A and so is my outlet. I plugged in the charger directly to the outlet and it resumed charging, but I presume a fuse blew inside the Kill-a-Watt. I've since gone to Google this and read horror stories with molten Kill-a-Watts, disfigured Kill-a-Watts, etc. So the device doesn't appear to live to its expectations of 15A limit. Maybe it isn't designed for long term measure of 12A current? Moral of the story, don't leave your Kill-a-Watt plugged in if you're charging your EV. I guess I can consider myself lucky that my Kill-a-Watt simply stopped working and there were no disfigured or molten parts at all.
I wouldn't be surprised if the internal wiring was undersized or not QC'd enough for a continuous 15A. The devices are pretty cheap and generally appear designed for lights or TVs energy measurement. My guess is the same would happen if you ran a space heater through the Kill-A-Watt.
Might be a bad unit of Kill-a-watt. I have been using Kill-a-watt to monitor my cost of charging for almost two years now without an issue.
Like salamander, I'm also using the Kill-a-Watt when I charge on 120V. No issues yet, I've only had it a few weeks though. It seems to be accurate considering what others are reporting. I use about 5.5kW/day (~5-9mi on battery before charge)
I've also been using the Kill-a-Watt when I charge @ 120V for almost 2 years, non-stop. It's worked flawlessly all that time and has never been unplugged from then loop..
I've used mine without any problems. I've also used it to measure the current on my miter saw doing a big cut (an 8/4 x 7 inch piece of maple), and I think it hit around 17A. The readout on the display flashes if the current exceeds 15A. But 17A for a few seconds isn't going to overheat anything. You should ask Kill-a-watt to replace your device (unless it's as easy as changing a fuse inside).
There are so many fake kill-a-watts out there, especially on Amazon and eBay and you'd never know without opening the case. The real Kill-A-Watts at least were designed to take the full 15A rating as peak and 12A continuously. I had a bunch of them on server equipment pulling near max draw 24/7 for years. However when I added a couple they were a slightly different colour but otherwise looked identical. After about 6-8 months, server UPS tripped online when the rest weren't and I go to check and the kill-a-watt is brown-ish and completely dead. Checked the other new ones and they were all hot. Old ones, still rocking. New ones, complete junk. Pretty sure they were fakes. I have a lot of them, and they looked identical. Someone who is just going off of pictures on the internet, I am not sure how you would know without opening it up, and that could be destructive.
My Kill-a-Watt says it's rated at 1875 Watts. My outlet is rated at 20 Amps I've never seen the Prime draw more than 1500 Watts when charging.
My first unit, very long ago, eventually suffered a failed solder joint on the current shunt. Re-soldering with an undersized home iron put it back in service for a while, but it eventually went intermittent, then failed completely again. A second one failed too, but I didn't troubleshoot it. Am wondering if it had a thermal problem, where different expansion rates predisposed it to mechanical joint failure.
Thanks for all the feedback. If it is so hard to tell if I have a fake kill-a-watt, then it may be possible I have a fake one. I've had it for nearly 2 years and used it occasionally for small loads. This was the first time I loaded it with high current approaching its limit. But to provide an update, I opened it up to search for a replaceable fuse. To my dismay, I didn't see anything that looked like a fuse or any removable parts inside. There aren't even signs of burnt parts while I examined it. I guess I will need to buy a new one. But now my concern is how do I make sure I get an original and not a fake?
