I'm sure there would be people that would try to work around the system, same as with every other law.

FYI - your pitch is equivalent to spying on call metadata vs content, which has been proven to be dangerous enough

How will this be difficult to fake? Just run timers on some appliances, or buy up cheap cryptomining gear that mines at negative ROI and run it.

Very easy, but it'd be tax evasion which is a serious crime.

Most taxes are pretty trivial to evade if you put some thought in to it. Very few people bother because the reward doesn't outweigh the risk. Saving a few tens of thousands of dollars a year isn't worthwhile if the penalty for being found out is losing everything you saved and years in prison. It's actually one of the few places in criminal law where the penalty actually works as a deterrent.

Next up: captchas to turn on the stove. "We need to make sure you're a human that wants to prepare food and not just a weird property owner that wants to pretend that somebody lives here".

See bidgely.com for one example.