I, for one, think it's a stupid idea.
First off, if people are left to choose whether or not to turn off their lights/power/whatever then 99.999% of people most likely will not do it.
Secondly, if the entire city is forced to do it (or in my case, my entire residence building) it will piss off a lot of people who need to spend that time doing homework (including research on the net), like, for instance, me. Also, the floodlights and emergency lights in the building, as well as the elevators, will still be active. This means there is still electricity usage. Additionally, the forced power outtage has not been advertised and I gurantee you that at least half of the residents here do not know about it, and will be using their computers, working on assignments at the time the power is turned off. This means their computers will shut down, and any unsaved work is lost nearly without warning. This will piss off a hell of a lot of people here, maybe even moreso than the inconvenience of losing an hour of working time. Also, we're not allowed candles in residence and flashlights won't cut the mustard as a light source for aiding in homework - not to mention the use of batteries and burning candles nullifies the point, as already mentioned in this thread.
Third, during this time, the power stations don't just stop producing power. They produce just as much power, producing just as much pollution. This power just won't be used during this time and will be stored/wasted/whatever. That nullifies any possible "environment saving" that could be taking place at that time.
Fourth, this will not change the whole climate deely one iota. If there is a man-made climate shift (which the jury is still out on, by the way - and those that agree with it cannot agree on how much influence it has had on the environment) this one hour of inconvenience won't change one damn thing. People will resume their normal energy-gobbling routines the second the power comes back on; just slightly more irritated.
I had more points, but I'm tired and brain decided to forget them. The whole thing is moronic and I absolutely hate the fact that I am being forced to partake in it because I live in residence.