If I'm not actively using my PC for anything it is shut down and turned off from the wall socket. 3 monitors and a pc on the same extension, even when they're not switched on still draw power. I'm in the UK though and electricity isn't cheap.

It takes all of maybe 5-10 seconds from power on to desktop, I've barely gotten comfortable in my chair before it's ready for my login, I can't see any reason whatsoever to leave my PC powered on, ever.