Copied from the FAQ:
Q: My factory only receives 10/20/50MW of power. How do I increase that limit?
A: Find the yellow arrow symbol inside the factory building, near the entrance, and hover your cursor over it. Now press Factorissimo2's increase hotkey [default: Shift+R] to increase the power limit to the limit you need, the maximum limit is 100GW. You can press Factorissimo2's decrease hotkey [default: Ctrl+R] to decrease the limit again. The reason factory buildings don't have huge power throughput by default is that more throughput requires a proportionally bigger power buffer for Factorissimo2's internal workings, and filling that buffer can cause massive brownouts especially early-game.
