Power companies will charge what they can, and to be fair most of their costs aren't generation, the guy who fixed that HV line a block over when the power went out during a winter storm? He doesn't work for free. And somebody paid for all those huge metal pylons or, if there aren't any where you live, the even more expensive underground cables.

But, the other practical effect is that if you use less fossil fuels you're making the climate worse more slowly. Now, given we'd like it to stop getting worse just making it worse more slowly isn't the whole answer but it does at least help.