You can use Task Scheduler to Shut Down your PC at a given time but I don't think you can use it to turn itself back on.
Your best option might be to schedule a sleep/hibernate low power state rather than a full shutdown, then to turn the PC back on you just click the mouse and it pops back up almost instantly.
Using sleep and hibernate does still use power, just less than if the PC was totally left on. If saving electricity was the primary concern, this might not be the best option.