Most large federated servers are hosted on VPS like solutions, not some old PC in someone's closet. They are very similar to the types of machines that large companies host centralized social media on.

As for other self hosted services. The small amount of electricity I might use more than using Google services is more than made up for by stopping the societal damage companies like that do. They fund politicians that fight regulation which does way more harm to the environment.

Focusing on a minute downside compared to the holistic damage these companies do is short sighted.

Can't remember the last time I poured millions into a fascist regime or gave technical support to a genocidal military. But yeah, I sipped a tiny bit more electricity last month.

Edit: also this issue is entirely solved by a push for clean energy and home solar. Both of which are heavily opposed by large corpo backed politicians.

There's a reason people with lots of money want our society to build multi billion dollar power plants and stop people from owning their own power generation. Because those with wealth can build and profit from those greatly, and can't make as much when people can afford to put solar panels on their homes.