If the cpu is doing work it’ll consume battery life. You get longer battery life from a system mostly in a low power state. An app will get the cycles it requir

If the cpu is doing work it’ll consume battery life. You get longer battery life from a system mostly in a low power state. An app will get the cycles it requires - it’s a trade off which usually means doing more work means less low power states. Less efficient apps will not enable low power as often. There is cooperation here and it’s why Apple didn’t originally allow background apps on the iPad.