Does keeping a computer on for more than 8 hours harm it?

[MMMjalapeno]

Does keeping a computer on for more than 8 hours harm it?

 

[kanewolf]

It adds run time to mechanical devices like hard drives. But if everything is properly cooled, there is little risk.

 

[USAFRet]

Does keeping a computer on for more than 8 hours harm it?

Except for reboots due to OS updates, and power off for moving house or vacation, a couple of my systems have been 'On' 24/7 for 6+ years.

 

[Paul NZ]

No. These go for 16+ hrs sometimes lol. Havent fried yet

 

[Solandri]

Except for the mechanical components (fans, HDDs), the thermal stress cycle of being turned on and off every day is actually worse for the electronics than leaving it on all the time. Sometimes you run across an old piece of equipment which has been on for over a decade. You unplug it to move it, and when you plug it back in it won't turn on anymore. It was fine while I was on all the time, but turning it off allowed it to cool, some parts contracted and broke, and it doesn't work anymore.

The main drawback of leaving stuff on 24/7 is the electricity consumption. The average price of electricity in the U.S. is about 11.5 cents/kWh, which by a remarkable coincidence means 1 Watt left on 24/7 for a year will cost you almost exactly $1. ($0.115/kWh * 8766 hours/yr = $1008 / kW - year = $1.008 per Watt per year.)

Most modern desktop computers burn about 25-35 Watts at idle. So if you left it in 24/7 for a year, it would cost you about $30 in electricity. If you're only actually using it for 8 hours/day, then 2/3 of the time it's on doing nothing. So that's $20 of electricity wasted every year. Not that big a deal for most people. I would recommend getting a UPS if you're going to leave it on 24/7 though. Not only will it help filter out power spikes and brownouts, it'll protect the computer from power failures (which to the software looks like a crash and can result in corrupted files).