nostr:npub1z2qdmfzhs2uwg8kmsh37xavt2hq48gch63e787ggd3s6mt8waxgsxu3yuf It might also be worth trying to install tlp (https://linrunner.de/tlp/index.html) if it's not installed.

It'll try optimize battery life, which usually means spinning down as much as it can. I've had good experience with it on misbehaving systems.

nostr:npub1z2qdmfzhs2uwg8kmsh37xavt2hq48gch63e787ggd3s6mt8waxgsxu3yuf Is it a laptop? Perhaps Ubuntu is setting the laptop to performance mode, scaling the CPU frequency up?

I'm not sure about Ubuntu 20.04, but on 22.04, that setting is visible when you click the battery icon in the top bar.