Kerbal Space Program

If you land a craft and run the engines to generate power you (assuming you're not moving) can enter time warp (rails time warp not physics). The engine animation will stop, fuel stops being drained but the power continues recharging.

I first found this with a jet I'd landed in a biome in Kerbin (during early career mode, before having solar panels). I was gently running the engines to generate power when I accidentally hit time warp. I noticed the fuel stop being used but the power kept increasing.

I tried it again with a rocket engine. I landed the craft a bit away from the runway and gently ran engines and time warped. Same thing, no fuel usage, but power was increasing. As a sanity check I also just time warped without first running the engines and the power did not increase.
Does not apply when in space as you can't rails time warp with the engines throttled up.
Not tried this on other planets, guess it will be harder to do on low grav places.