Bitcoin may seem sexy, but it’s a huge problem for the climate. A single Bitcoin transaction expends enough electricity to power the average US home for three weeks—and that energy is coming mostly from fossil fuels.

Bitcoin is “mined” using computers to solve increasingly difficult problems. It’s that mining process that sucks down so much electricity.

To be clear, blockchain technology is not inherently energy-intensive, and there are some amazing uses for blockchains. It’s the proof-of-work verification method that Bitcoin uses that is the problem. Other cryptocurrencies use proof-of-stake verification methods that do not require obscene amounts of energy.

This can all be pretty complicated for anyone not deeply tech-proficient. But what most of us need to know is that Bitcoin is making a few people rich, more people greedy, and all of us more vulnerable to a warming world.