Still, inductive current measurement with the sizes of the clamps they show and typical currents they're measuring isn't accurate at all. Not even considering that voltage measuremens via a wall wart would depend on what load is currently sharing the same wiring.
This might be my bias since I design similar stuff for solar offgrid, where a percent or ten off are that much in capex divided by battery lifetime, then multiplied by battery cost. It bites.
I don't trust inductive clamps at low currents. I would never trust measuring voltage on the same line as a load.
Hall sensors or current shunts; voltage dividers - all driving MCU ADC channels via optoisolated opamps. Everything measured as near to the source as possible. Otherwise you're getting nearly worthless data.
That's actually not correct. Clamps / current transformers are totally fine.
A toy, in other words. It might be good enough to get a rough idea what eats more or less and when, but it'll never match the utility power meter which is what you're paying by.
cdrc: I rewire my houses myself, because those licensed loons can't be trusted with a 12V light bulb. At least that way _I_ am sure it won't blow up or burn or whatever.