Surely you have at least once had to download a large file, and have left the PC on to continue the download while you aren´t there. The inconvenience of this process is that you waste energy, as the download will probably finish long before you return (ie overnight). The solution is called Auto Shutdown.
Auto Shutdown is an add-on for the
Mozilla Firefox browser, which works to program the PC shutdown when it finishes any download activities. To activate it or deactivate it, you can use the program´s icon, which is in the browser status bar. Easy and practical.