Leaving your PC on unnecessarily is a bad idea, and not just for environmental reasons - it's also a waste of money. Just four hours of pointless idling a day could add £40 to your annual electricity bill, perhaps more for a high-end system. We'd hazard a guess that you can think of better ways to spend the cash.
Shutting down your PC when it's no longer required really does pay, then, and AMP WinOFF provides plenty of tools to help. In a few clicks you can schedule your system to shut down at a specific time and date, or you can ask the program to turn your PC off in a specified number of minutes.
If you've left your PC running some complicated task - video encoding, say - then of course you may not know exactly how long this is going to take. But AMP WinOFF can help here, too, by shutting down your PC when the CPU is idle.
And while by default the program will power down your computer, it also provides full access to all other Windows shut down modes. So you might for example schedule an unattended system to restart every day, to avoid problems with memory leaks. It's also able to suspend or hibernate your PC, lock it, and more.