How much does it cost to power your PC?

Ed Bott of ZDnet has been measuring his PC power consumption.

Not surprisingly, you save a whole lot of power by using S3 sleep mode to dramatically reduce power draw during times when the PC is turned on but not being used. Bott seems to suggest that S3 is something that Windows Vista offers and XP doesn't. I'm not an expert in this realm, other than to report that sleep or "suspend," as it's often called, rarely works in most Linux distributions, and that these days a lot of effort is being expended to get suspend working in laptops under Linux.

But here's Bott on S3 in his experience:

I ... attached a Kill A Watt meter to the Dell C521 PC that I’ve been using for my ongoing Media Center experiments. At rest, it uses about 64 watts, and its power consumption is roughly equivalent to the HP server over time. However, it’s dramatically more power-efficient, thanks to Windows Vista’s sleep mode. In the past 24 hours, it has used less than 0.5 kWh. Over the course of a month, that’s about $1.20 in electricity. The secret of its power-saving success is S3 sleep mode. When this system kicks into S3 mode, it uses a mere 3 watts, according to the Kill A Watt device. That 0.5 kWh equals 8 hours a day of full-power usage, coupled with 16 hours in sleep mode. If I were to leave it on with sleep disabled, energy usage would triple. Using the default Balanced power settings for the three PCs in this house will save more than 1000 kWh over the course of a year, or $82.

He promises more on S3 mode in a future entry. I'll be looking for it.

Suspend works great on our iBook G4, but with Apple and OS X, you expect stuff like that to work -- and you usually get what you expect.