I'll do the napkin math for you.

Every day 144 blocks are mined, every block rewards the miner 12.5 + 0.1555 BTC. So every day 1822,392 BTC (= $16,4 million) is given to miners (on average). If you assume for every BTC a miner mines he pays 0.5 BTC in electricity (not sure how accurate this is, just estimating) than that would mean $8,2 million spent on electricity daily. If we assume an electricity cost of $0.06/kWh that comes down to 273.3 136.6 million kWh daily. If we consider 300,000 txs per day we get roughly 910 455 kWh per tx. Which is what the average US household consumes per month 15 days . So that's even worse than what the original post said.


Again this is really rough napkin math, if you want more accurate estimations, go to the link I put in the OP, it is way more accurate :p

EDIT: Thanks Mike Mayor for correcting my math