Is it better to leave your computer on all the time?

A couple of years ago, the company I worked for had a corporate-wide policy that insisted all desktop computers be left on overnight for automatic OS, software and anti-virus updates. This process took about 30 minutes around 4am in the morning. Last people left work at 7pm and first to arrive were at about 8am. So 12 hrs 30 minutes of unused time. All monitors were asleep, any connected hardware would have been in "sleep" mode if available.

150 or so desktops. Compaq Evo P4 things, roughly 45W per desktop. 6.75kW - just for the building I worked in. The PCs couldn't go into standby, owing to the software updates (and the management system installed on the PCs that did that).

I did suggest we use this uptime by installing Boinc or another distributed processing management platform. There's lots of mathematics you can do with all that computing power (protein folding, economic modelling etc...) and I figured it was quite a saleable asset.

Couldn't really get any takers at the time. Maybe now we're all suffering high power bills and climate change is widely accepted as actually happening, I may have more success now.

If I know I'm going to be away for anything more than an hour and I have nothing running/scheduled (defrag, AV, etc.), I shut down.

the only problem with leaving the desktop on all the time is dust. but with a regular maintenance (defrag, av and hardware cleaning) everything will work just fine

Well it depends how much power it drains. Personally I put my main computers to sleep and all peripherals off. I do have a tiny mac mini that dutifully backs all my data up to Mozy 24/7 and draws a maximum of 50watts while doing that.

Personally I try to save power and I try to keep my beast of a main computer on only when I need it. It is kinda pointless to be using 400 watts for a screensaver 24/7

But thats just me in the UK!

On any machine I've ever owned, I've kept them on 24/7. I constantly monitor temps, so unless a fan dies unexpectedly, I'll be fine. Except my 'toaster' PC. Gaming only, so I shut it down when it wasn't in use.

I always shut down every device expect for my cellphone at night when i go to bed.I always like to sleep in a eletricity free space.I dont care if turning off the computer harms anything.i rather feel safe at night.

Yes, but you could get a higher bill and the PC might get hot...

during the day i lock my desktop and laptop when not in use and my desktop goes on standby by its self at 12:00 at night, but i normal just switch of my laptop if i don't think i'll use it again.

I have a Mac Mini and it can be very slow to start up. Unless I know I won't use it for a couple days, it is just easier to keep it on all the time. I put it in sleep to help conserve energy. If you use your computer all the time, I would say leave it on.