Well this site says that the bitcoin network uses at least 91 TWh annually.
According to fediverse.observer, there's roughly 21000 Fediverse servers online.
Let's just assume that a server on the Fediverse uses 500W. That's quite a high estimate btw, but we can overestimate, it's fine.
That gives roughly 0.09 TWh annually, or about 0.1% of the bitcoin network. And remember that's an overestimate and remember that that only considers bitcoin and no other cryptocurrencies.