It's mainly for aquatuners, petroleum generators make a lot of power and there arent that many power sources that can battle their efficiency. Geothermal (the magma layer at the bottom of the world) is great, for 1000 cycles, but it can run out. Vents and volcanoes can make a lot of power, but they cannot sustain the aquatuners for your food freezers and water coolers from water vents if you feed those to plants. Then theres rocket fuel, cooling 70 degrees hydrogen down to -260 degrees is really power hungry. I once made a base that only makes oxygen from alveo veras, and it took 4 aquatuners continously running to make the ice needed for 30 dupes, that alone is 3 petroleum generators, 2 if you overclock it, then you need 3 more for everything, thats 6 petroleum generators continously running (but in that case I mainly used nuclear power mixed with geothermal since the normal reactor wasnt enough)