There’s advice flying around the ‘net today about how much energy we save by shutting PCs off when they’re not in use.

Having widely dispensed the advice to leave PCs on all the time (but I’ve been saying for 15 years to turn monitors off), let me be the contrarian and talk about the counterpoint.The issue is the amount of energy an idle PC wastes doing nothing. And that’s the main reason I’ve always recommended turning monitors off–monitors use a lot of energy and give off a lot of heat, and there’s no particular advantage to leaving them on either. Picture tubes degrade rapidly if they’re left on all the time–this is why every monitor in a used computer store requires you to turn the brightness and contrast all the way up for the display to be readable. Turning the monitor off and on repeatedly isn’t good for it either, but it saves the picture tube.

Now, on to the PC. My PC on its own consumes less electricity than the light bulbs in the room it sits in. Energy costs are going up, but that’s still only a few dollars a year it’s burning. In the 15 years I’ve been leaving computers on all the time, I’ve had a very small number of hardware failures–I’ve lost maybe four hard drives, and one or two power supplies. And I own a lot more computers than the average person. That averages out to one repair every two years on a house full of computers. If I were having to replace a hard drive every year, I’d be spending more money.

Aside from the money, how much energy am I saving by not having to replace lots of parts every year? Isn’t the increased lifespan of my computers worth something?

That’s not the only issue, of course. A computer generates some heat, and in the summer you have to get rid of that heat. But rather than turning PCs off all the time, I prefer to minimize their power consumption. If I don’t need the hottest new 3D video card (which I don’t), then I don’t use it. And the majority of my CPUs are in the gigahertz neighborhood. They do everything I need. So I save energy that way. I get energy savings elsewhere (by using compact flourescent bulbs, for example), so to me, leaving the PCs on makes sense.

In the winter, of course, the heat given off by PCs is a nice benefit. The more heat my computer gives off, the less work my furnace has to do.

I think some common sense is in order. I turn my monitors off when they’re not in use (though LCDs use little power, I recommend shutting them off too in order to conserve the backlight). The PCs I use every day stay powered on. PCs that I only use occasionally–say, once or twice a week–get powered down when I am finished with them for the day. Admittedly I’m more likely to leave a little-used PC powered on in the winter or summer.