The chips themselves would depend on the exact chip design tech. The newer the chips are, usually the less power they need. the CMOS based chips use a bit less power than the older ones.
In general, the chips use 5V. Exact number depends on the specific chip and sometimes, the operating speed. Mobile chips use less.
The computer itself use anywhere between 100 to 1000 watts depending on parts inside. Video cards probably use the most power, then hard drives and optical drives (when they're spinning).