Yes. System Idle Process does not execute instructions, not even NOPs. It is instead in one of the power-saving idle states, where much of the cpu is turned off until it receives a hardware interrupt.
Then I'm going to stop running Folding@home, then.
ETA: I'm still going to leave my computer on at night, though, because it often freezes shortly after booting, but leaving it on lets me avoid this problem.
Latest in an irregular series, some of whose previous entries were Edge.org and the Girl Scouts...
I examine the Folding@home distributed computing project with reference to the costs (electricity resulting in air pollution causing deaths) and benefits (some papers): http://www.gwern.net/Charity is not about helping. Additional data on either side of the cost-benefit is welcome.
(I also recently split out my essay describing things I have changed my mind on.)