Oh I love this stuff.
My dishwasher pulls over 1000W, but overall actual usage pales in comparison to my server cluster, which utilizes a multiple 35W mini PCs.
I started measuring a bunch of things in February (using zigbee-compatible smart plugs to HA), so here is a graph of the above for the entire month of March:
It was eye opening, to say the least.
The env variable is within the compose file itself - it's fairly simple.