> I've heard so many times that it's renewable energy being used because it's so cheap.

It's a myth from the pro-cryptocurrency crowd.

With recent price spikes, mining is profitable even if you have to pay relative high prices for electricity. You don't need to have cheap energy.

Also, it's another myth that we have an abundance of hydroelectric power that would otherwise go to waste if not for Bitcoin. With modern power transmission it's trivial to send power through the grid to other locations, and nobody is building power plants in the middle of nowhere without a way to send that electricity somewhere else.

Finally, Bitcoin's power consumption is additive. Energy that goes into Bitcoin mining is energy that isn't being used to power cities and other infrastructure, which must still get its power from somewhere.

Don't believe the whitewashing campaigns to downplay Bitcoin's energy usage. It's very bad.

That's a fair opinion but is there any data on that?

The upper bound on environmental harm is the damage that would be done by the most harmful energy production method used: any renewable energy spent on mining could be used instead to replace that harmful production.

(It's only an upper bound because energy isn't perfectly fungible.)

Renewable energy is also better than fossil energy in terms of environmental damage, but it's not free from damage. A dam is a massive localised environmental impact, and a huge amount of concrete. A solar farm requires (holes-in-ground) mining and significant industrial processing to build. The lower bound on environmental harm is the cost of building renewable energy sources that are used for something so unproductive.

Sure but that dam is already there. So why not use the spare energy on something?

Or is there energy being "stolen" from other uses?

As I wrote: is there any reliable data?