How much power does a computer use?

Computer power supplies are rated for certain wattages based on their maximum output power. Typical rated wattages range from 200 W to 500 W, although units used by gamers and enthusiasts usually range from 500 W to 800 W, with the highest end units going up to 1 kW (although 1.1kW and higher power supplies are available for extreme performance computers with multiple processors and graphics cards (eg. ATI CrossFire or NVIDIA SLI)