There are a lot of coins that dont't use PoW. Ther are even some that you could argue have a net savings effect on electricity.

For example Gridcoin: The chain moves by PoS mechanism, but the coin also rewards work. Not the meaningless hashing work like Bitcoin, but actual research.

A lot of researches are in dire need of more computing resources and funding. some put up their work to the volunteer network BOINC.

Gridcoin now pays the crunchers by distributing the cryptocurrency based on the amount of work done.

Depending how you use it and on which hardware, this is extremely effective (e.g. on smartphones or on your desktops only when they are running anyway), more effective then on a scientist's lab supercomputer.

If you let your computer run just for Gridcoin it may be less effective, but if people crunch Gridcoin (Science) instead of POW coins then it again is either saved POW energy or additional science done.

Either way better then Bitcoin. Now someone just needs to pump the price so that the PoW workers change their coin ^^