A few years ago I built an integrating digital power meter based on a design by Brand Electronics.
http://www.brandelectronics.com/powermeter.htm
These things are extremely useful as they allow you to measure intermittent loads (such as a refrigerator) and any sort of AC waveform. Measuring loads around the house produced some startling results...
Our "instant on" TV idles at 19 watts, the stereo receiver at 15 watts and the set top box at 25 watts. The vampire cubes (the AC/DC power converter cubes that have two teeth, are generally black and suck electricity) are all between 2 and 4 watts loaded or not. By judicious use of a few power strips we were able to eliminate an 80 watt phantom load in our home. That's 700 kwh a year or nearly $80 at our rate! The national average for electric generation CO2 production is 1.5 pounds of CO2 per kwh .. so that is about a half ton of carbon dioxide for no reason other than convenience.
Replacing the refrigerator and air conditioner when they died made a huge difference, but looking at PCs turned out to be interesting.
My Titanium Powerbook averages about 17 watts under normal use and drops to 2 watts in its sleep mode. Sukie's Cube and 15" lcd is 68 watts under normal use and 7 watts sleeping. The dual processor G4 Powermac and 17" lcd weigh in at 168 watts and just 9 watts during sleep.
These are dramatic differences. Arguably moving to a laptop is eco-friendly.
What really surprised me was measuring a few P4s and Athlons. A friend's new over 2 GHz tower with a high end video card and a 21" CRT used an astounding 513 watts! Several of the machines exceeded 400 watts and none were under 300.
The 513 watt monster was too unreliable to sleep (it did it once, but somehow installing a piece of software removed that capability) Assuming 5 hours of use a day we get well over 900 kwh a year. If the thing was on all day (unlikely as it sounds like a wind tunnel) we are up to about 4400 kwh a year - about $500 where I live.
At some point I wonder if people have to think about what their computational needs are and buy appropriately. Perhaps it makes sense to mark PCs with energy usage stickers like other household appliances.
8:09:01 PM 
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