You can definitely do this with ZigBee, I have smart light-switches that report usage; though I'd argue the lights are the least useful thing to have usage repo

You can definitely do this with ZigBee, I have smart light-switches that report usage; though I'd argue the lights are the least useful thing to have usage reporting for, since I already know the power consumption of the bulbs, and since I'm using LED everywhere, it's negligible compared to the rest of my usage. The problem with ZigBee is network scale and interference, but also you're wasting energy by having electronics in every socket, always on, always reporting. You're also then driving your server harder and storing more data, costing more. I've aimed to strike a balance of only making smart the things I actually care about power usage for; my server rack, my 3D printers, my desk, and then whole-home as a single unit. I don't need to know how much my washing machine or oven uses, if I need to use them, I need to use them; there's little room for optimising. When it comes to optimising which settings I use, if I care enough, I can use a temporary ZigBee power meter that plugs in like a normal device; record data for days/weeks/months and adjust based on the result of that.