It appears that's the case but I've read a lot of bitcoin is mined using power sources that are under utilized and otherwise not practical to keep using. Much off this includes green energy which might have a better ROI in its early stages with bitcoin hovering it up when it's excess can't be sold. It's fairly easy to just switch to proof of stake though if ever this issue is forced hard enough by energy providers.
And that huge computing power is employed to basically solve Sudokus whose difficulty is adjusted to burn as much energy as is put into it (which unscrupulous people will do as long as that energy is still cheaper than the mining rewards).