Brightrev

The average desktop PC uses about 100 watts of power while it's running. Computers still take a long time to start up, so I understand why some people leave their PCs on rather than shut them down after every use. But when you start to add up the costs, leaving your computer on actually adds up to quite a bit of money over the course of year. With the improvements in Sleep mode in Windows Vista SP1 and the excellent power management built-in to Mac OS X, you can save money, power and have a PC that starts up quickly. Continue reading to find out how.

Windows Vista SP1 and Mac OS X have similar and very effective sleep modes. Both operating systems put the computer sleep in about 10 seconds, powering down to a state where they only use a few watts of power. Unlike when they perform a full reboot, both Macs and PCs power out of sleep mode to a full, usable desktop in about five seconds.

There are several reasons you should use power management on your computers. First, if we assume a modern desktop PC uses about 100 watts of power, we can calculate the yearly cost of leaving a desktop computer on all the time. According to the US Government's Energy Information Administration, the average cost of electricity was 10.31 cents per kilowatthour in December 2007. If we divide 100 watts by 1,000, we find that a desktop computer uses .10 kWh. Multiplying .10 kWh times 24 tells us that a computer uses 2.4 kWh per day it's left on. Here's the cost breakdown per week, month and year, based on the average price noted above.

Cost of leaving a desktop computer running

Let's assume you use your home computer 4 hours per day and you put it in sleep mode regularly, you'd save more than $75 in electricity costs per year. However, money isn't the only reason to put your computers into sleep mode. Global Warming is a worldwide problem, and we're all acting in our own best interest by cutting power use wherever we can. If the climate change argument doesn't sway you, try going into your home office, closing the door and shutting your computer down. Hear that? That's the wonderful sound of silence. You don't generally notice the white noise a computer creates when it's running, but the silence is noticeable, especially when you need to concentrate. Finally, if you live in a hot climate (like I do) and your office is on the sun side of the house (like mine is) the summer heat reduction alone is enough to justify powering down your computers.

I should mention that there are alternatives to using a desktop computer. Laptops typically use about 20% of the power of an equivalent desktop. Shutting your computers down completely is also an option, especially if you only tend to use them once per day. Here's how to configure sleep mode on Windows Vista and Mac OS X.

Windows Vista

To configure your PC to sleep on Windows Vista, click Start -> Control Panel. Type power in the search box and then click Change when the computer sleeps.

I set my monitor to turn off after 10 minutes of idle time and my computer to sleep after 30 minutes, mostly so it doesn't go to sleep when I'm sitting in front of it.

I also put the computer to sleep when I walk away, which is the default action for the Start -> Power Button in Windows Vista.

Mac OS X

To configure your Mac to use sleep mode, go to Spotlight and search for System Preferences, or click the icon in the Dock.

Click the Energy Saver icon and then adjust the inactive slider to the amount of time you'd like to use.

You can also put your Mac to sleep by clicking the Apple and then Sleep.

By using your computer's sleep mode, you're saving money, cutting heat and noise and helping the environment.

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