Are you talking about a desktop? I am on a laptop with Intel iGPU and Nvidia dGPU. The battery life in Windows isn't great, but it actually seems worse in Pop OS. I did actually catching it using the dGPU when it shouldn't be. Obviously Nvidia doesn't help things, and I am glad it works as well as it does. Still it's kind of sad. I might buy a second laptop just so I can have battery life that isn't horrible.
Cosmic desktop from my understanding will have a better implementation of the hybrid graphics mode to stop this nonsense.