Is it better to put your computer to sleep at night, like a little electronic baby, or shut it down to save energy like a good global eco-citizen?

The minuscule amount of energy, if any, saved with a nightly shutdown won't reduce anyone's carbon footprint much but could shorten your computer's life. The daily on-off stress isn't good for your computer's heart. It'll only lead to an early trip to the landfill or recycling center.

"A power cycle, which is turning a computer off fully and then turning it back on, should be relegated to a maintenance activity on approximately a weekly basis," says Damian Giannunzio, director of Iolo Labs of Los Angeles, which studies PC performance and stability.

Giannunzio, whose research contributes to the development of Iolo Technologies' repair and optimization software for Windows PCs, says he runs his own computer in balanced power mode. This default Windows setting provides peak performance only on demand.

"Having done a significant body of testing with the different power modes," he says, "I'm actually quite pleased with balanced. It essentially permits the [processor] cycling to match up with your activity on the system. … Significantly, it doesn't throttle your productivity like a low mode would."

Even gamers should question whether Windows' high-performance power mode, with maxed-out screen brightness and processor constantly in high gear, is worth higher operating temperatures, increased power consumption, more noise and shorter life span.

"High performance, in my mind, is terrible," Giannunzio says. "It is absolutely not worth essentially removing any sort of limitation on [the processor's] frequency. It's no longer intelligent or adaptive.

"When you go into high-performance mode, you're letting it run at peak speeds all the time. That is death to a system. At low mode, you do end up seeing a penalty, which is activity and speeds of the system."

So run your PC in balanced power mode and put it to bed each night in either standby or hibernate. Standby uses little power and awakes faster, while hibernate uses no power but revives slowly. (Apple computers have adjustable energy-saver sleep and idle modes.)