Actually, peak-load power stations are designed to have their output varied across the day, it's the base-load stations that run at max efficiency 24/7. To me, Earth Hour needs to be turned into Earth Day, except that it's not lights that you turn out but useless standby crap, and minimising the amount of electricity you use whilst still doing everything that you normally do. Earth Hour only makes the old-farts feel nostalgic about the Blitz, young people complain that they can't play their X-Box for an hour, and candle manufacturers roll around in the piles of cash they make from increased sales. For it to be of any use, it needs to be more than a 1 hour sacrifice - make it a 1 day or 1 week compromise, and you'll see much better results from it. That, and the more you do it the more it will become second nature.