I've thought of a good way to put this perspective. The block reward is 12.5 BTC (and fees are neglible), which is $100000. There's a new block every ~15 minut

I've thought of a good way to put this perspective. The block reward is 12.5 BTC (and fees are neglible), which is $100000. There's a new block every ~15 minutes, which means 35000 blocks per year. ($100000 * 35000 / 73 TWH) = $0.048/KWH. So miners spend at most $0.05 per KWH on electricity. Assuming they spend 60% on electricity, they spend ~$0.03 per KWH, so not an outrageous price. The problem is BTC grew too big too fast. The block reward is very large, but once it drops to the magnitude of fees ($2000 / block), we'll probably see a decrease in the energy usage to the (perceived?) value of decentralized payment system. Also, this shows the need for governments to drastically increase taxes on carbon producing forms of electricity.