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About a year ago, I began thinking about how much electricity my computer used. I’m not talking about using my computer, but about not using it. Really, how much of your computer do you really use? I’m watching the resource meter right now as I’m typing and the CPU history rarely spikes above 25%. That’s when I’m “using” it. Most of the time it spends on, I spend in the other room.

Your computer power supply is rated in Watts, just like light bulbs, and is built into the design of the whole computer to handle the maximum power load that all the hardware could possibly require. For average systems, that maximum rating is somewhere between 250-400 Watts. However, higher-end hardware such as hefty video cards for gaming or large monitors, multi-core processors, cooling fans, multimedia encoding/decoding, optical disc drives (say, burning DVDs), multiple or high-speed hard drives, or other power-hungry components can bump that peak demand above 1000 Watts. Most of the day you probably float at less than half your peak power. Even so, your computer can easily draw 100 Watts idling. Did you ever think of your computer as an extra light in your house, one that you leave on when you leave the room, or, like some people I know, while you’re sleeping? Sure, I try to turn off my computer when I don’t need it (I usually get more done then anyway), but sometimes it’s just not practical. When that extra proverbial light bulb needs to be on, wouldn’t it be nice to dim the lights when only need mood lighting or you leave the room, while still enjoy the brightness when you need it? Enter Granola.

Granola is software that does just that. It emerged out of beta on Earth Day 2010 and, best of all, it’s free and runs on Windows and Linux, and may be planned for Mac OSX down the road. Formerly MicroMiser, Granola was renamed to “more accurately capture our goal of making a serious impact on the planet through the reduction of wasted energy,” says MiserWare, the company behind Granola. According to the email they sent me announcement the newest version: “There are over a billion personal computers in the world. Together, they consume hundreds of billions of kilowatt hours annually. If each of these computers ran Granola and reduced their power consumption by even 10%, it would be like taking 7 million cars off the road. Or planting 900 million trees. Or turning off 65 coal power plants.” So far, they claim that the Granola community has saved as much CO2 as tens of thousands of trees. That’s assuming that every download equates to “average saving” of 56.9kWh and runs on a computer 24/7. Even though it seems that reported numbers are best-case scenarios based on assumptions and averages, I think more awareness of green aware computers is needed. And to be honest, if there’s any chance of reducing my home power use, I’m interested.

I have Granola running on three linux computers at home: a newer quad-core CPU computer, an older single-core CPU computer, and a small server with an low-power Intel Atom processor. Granola saves a bit over 45% CPU energy on all three, and claims to save about $25/year each, after setting our local energy rate to $0.10/kWh. Scale that by how often they’re on, and the savings comes to about $40/year. My wife claims to notice her computer runs a bit slower, but I don’t notice much change on mine. Next step is to find a Kill-A-Watt meter to check the power savings.

But Granola can only throttle the CPU power. Other managements are built into your operating system to quell power draw, such as timed monitor power-down, spinning down the hard drive, or hibernating, which are especially appreciated on laptops. The sure-fire hacks to save computer energy still remain: use laptops instead of desktops, turn them off when not in use, and don’t buy higher performing systems than life demands. But if those don’t work for you, Granola can bring some peace of mind and a little green to your CPU.

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