I was recently criticized by a conservation-minded friend for leaving my computer on all the time. As I consider myself a fairly passionate environmentalist (at least in some areas), I took her concern seriously, and did some research. That is, I asked Pete, who is very knowledgeable in these things. Here’s a summary of what I learned.

I leave my computer on for a number of reasons. For one, other people need access to it even when I’m gone. That may or may not be true for you, too. Plus, my back-up software runs every night.  Gotta have that! (When do you do your backups?)

There’s also the convenience factor. Since I work at home, I tend to take a break every so often to run downstairs and fold laundry, go outside to feed our hens, make lunch, etc. I’d be turning my system off multiple times a day, and then waiting each time for the five minutes or so it takes to come back up again. In the evenings, I like to chat with my kids on AIM, check the weather prediction, comment on Facebook, read the news, etc., so again, I’m using my computer frequently. If your computer is at work, by all means shut it down when you leave for the day.

Repeatedly turning your computer off and on does wear it out. Many articles assume you’ll be replacing your computer before this matters. That’s not necessarily true. While a lot of corporations buy all new computers every three years, that’s a luxury most of us can’t afford. You might save electricity by turning things off, but that savings needs to be balanced against the energy and other resources that go into making the replacement computer you’ll need sooner than later.

So, are there times when you should turn your computer off to save energy?

Let’s start with simple things first. Try setting your screen saver to shut down your screen when you’re not using it. It’s very easy, and you don’t have start again from scratch—just wiggle your mouse.

Powering down your monitor is great, but doesn’t affect your entire computer. The next step is to put your CPU to sleep. An article from the US Department of Energy states:

ENERGY STAR® computers power down to a sleep mode that consumes 15 Watts or less power, which is around 70% less electricity than a computer without power management features. ENERGY STAR monitors have the capability to power down into two successive “sleep” modes. In the first, the monitor energy consumption is less than or equal to 15 Watts, and in the second, power consumption reduces to 8 Watts, which is less than 10% of its operating power consumption.

Make sure you have the power-down feature set up on your PC through your operating system software. This has to be done by you, otherwise the PC will not power down.

I found the power-down feature on my computer by clicking on the Start button, choosing “Settings,” then “Control Panel,” and then “Power Options.” Note that your computer may not go to sleep if a screen saver is running.

Finally, the same article recommends turning off your entire computer if you’ll be away for more than two hours. This advice is based on average energy consumption for a running PC compared to the extra electricity needed to start it up again, and doesn’t take into consideration the other factors I mentioned above.

Obviously, if you only use your computer infrequently, say a few hours every day or two, turning it off when you’re done makes a ton of sense.

If you want to save every possible kilowatt, you can go one step further. Like TVs and other electronic equipment, computers, printers, and other peripherals consume some electricity even when they’re not turned on. Plugging everything into a power strip, and then switching off the entire strip when not in use, ensures that no power is drawn at all. (Power/surge strips have the added bonus of protecting your equipment during thunderstorms. Get the cheapest one you can, since in this case, you want it to “fail.”) Or, you can just unplug everything when you’re not using it.

In short, the decision of whether to turn off your PC or not depends a lot on your particular circumstances. Yes, it saves energy. However, if you use your computer a lot, it might not be worth the time, and the wear and tear on your equipment, to be shutting it down all the time.

How about turning off the TV instead?