A 125VAC Kill-A-Watt has come to my hands, but in my country, the grid operates at 220VAC.
I know I can't use it as-is, but is it possible to modify it to be usable?
Ask sales for availability of the 220Vac unit by email/ It shoukld be easy to adapt with the correct p/n component changes, an adapter cord pair and perhaps an MOV protection clamp with proper HV rated series line 1MOhm resistor.
I believe this may be the schematic for 220Vac using the same chip used in the 120Vac kill-a-watt. They are cheap,but how accurate depends on attention to many details.
The kill-a-watt unfortunately does it's own RMS conversion, and does not use a off-the-shelf power monitoring IC or anything.
Also, the controller IC is unfortunately, a epoxy-blob device, so it's not possible to easily reverse engineer it, or even determine what it is. The only IC I could look find the data sheet for in the kill-a-watt I took apart a while ago was a simple quad-op-amp (a LM2902).
Overall, I think it would probably be easier to build your own, rather then try to convert a existing kill-a-watt.
Anyways, no matter what you do, there is really no way to make the voltage readout work properly without a firmware change, so I can't see how useful even swapping some parts would be.
Note the high-quality soldering job. It was like that from the factory.
I did this tear-down a few years ago, and I've been just too lazy to actually post it anywhere.