Moving value around isn’t free. It takes money and energy and human time. Bitcoin is more efficient than the traditional banking system in many ways. You just don’t see headlines about how much energy is used by the stock market or remittance services because it’s not good clickbait. “BITCOIN IS BOILING THE OCEANS” however is novel and sounds good. But it’s just clickbait.

Bitcoin uses <1% of global energy, mostly from renewables, at off-peak times since it’s the cheapest energy. Miners have to use the cheapest energy (as mining is extremely competitive and low margin), so they don’t compete with regular energy users. What they do is even out demand curves, which ultimately incentivizes the addition of renewables to the grid by ensuring there will always be a buyer for the electricity. This keeps prices down for regular users as well, since they aren’t paying for un-used capacity. Proof-of-work is essential to Bitcoin’s security, other schemes have been attempted but do not stay decentralized as well, are less secure, and tend to lead to concentration of wealth.

That’s all to secure “main chain”, but a single main-chain transaction can open a lightning channel which can contain billions of transactions, none of which need to be mined, all of which settle in under a second for next to nothing in fees. Main chain “secures” these transactions but doesn’t need to actually process them, which means lightning transactions take about as much energy as sending an e-mail.

If you’re interested in learning more about Bitcoin’s energy use see https://endthefud.org/ or for a more friendly and less academic site see http://bitcoin.rocks