I had the same idea; a computer that is done with the task you've given it will run some do-nothing idle code that doesn't take appreciably less power than the

I had the same idea; a computer that is done with the task you've given it will run some do-nothing idle code that doesn't take appreciably less power than the task you gave it. The article did mention a case where the difference would be noticeable though - if the program is running on a shared server like AWS, another useful program might take over once yours is done.