Most computers come with a 230-350 watt power supply. That doesn’t mean it uses 350 watts, but that is the max it can provide. So how much does your computer need?
A typical computer will use about 70-100 watts. How much you actually need depends on your hardware requirements. Don’t think for one minute you need a 1500w power supply.
Add up all the various power requirements from the various devices and see what the total is. You can also get one of those in-line watt meters and see how much power your pc is using.
How much does your computer cost to run? Let’s say you have a big high-end computer and you leave it on 24/7. That’s about 200 watts x 24 hours x 365 days/yr = 2,890,800 watt-hours, or 2891 kilowatt-hours. If you’re paying $0.14 per kWh, you’re paying about $245 a year to run your computer. (ouch)
Let’s say you have a computer that’s less of an energy hog, and it uses about 105 watts, and you to turn it off when you’re not using it. You use it for two hours a day, five days a week. That’s ten hours a week, or 520 hours a year. So your 105 watts times 520 hours = 54,600 watt-hours. Divide by 1000 and you have 55 kilowatt-hours (kWh). If you’re paying 14¢ per kilowatt-hour, then you’re paying $7.64 a year to run your computer. Big difference huh?
Having trouble convincing someone to switch to a LCD? A typical 17″ CRT uses about 80w. The same size LCD uses about 35w. No matter how much you use your monitor, an LCD saves you 43% every month. Depending on the cost of power, it can pay for itself in under a 2 years.