Tell you what - in this thread I’ll be the iron fist of information in the velvet glove of diplomacy; you can be the cricket bat of enlightenment whanging on the groin of ignorance. 
Heh.
And thanks for the additional info. I hadn’t though about additional factors in maintaining a minimum operating energy expenditure other than electrical loading. My Electrical Engineer’s Reference Book doesn’t cover the mechanical aspects of power generation so much.
It’s far worse than that. If you don’t leave all your lights and appliances running all night all the electricity gets backed up on the lines. One day it’s going to overflow all the way back to the generators and all the power workers consoles will explode, like on Star Trek, and the power station will be knee deep in electricity.
So just think about the lives you’re putting at risk next time you selfishly switch your lights out.
This thread has now reach its terminus, having called at OP, Unenlighted Speculation, Expert Analysis and finally Flippant Sarcasm. Would all dopers make sure they have their luggage with them when they disembark.
I have no expertise to add. But this reminds me of a story a friend told me. There was a sign in his university physics department corridor that said :
Conserve energy- please switch off light bulbs when not in use
Under which some wag had written:
**First Law of Thermodynamics: Energy is always conserved. **
Eh?
Seems to me the OP was correctly answered early on, and that Una and I are substantially in agreement on this point (though I don’t wish to speak for her). I see nothing in Una’s excellent post that “debunks” anything in my initial post, but if you do, would you be so kind as to point it out to me? I’ve conceded to a misunderstanding of minimum load conditions, but this has no real bearing on the OP’s question; it only means that fuel usage is not necessarily linear to demand.
Q.E.D.,
In no way was I intending to refer to any post of yours, in this thread or any other. I apologize if you interpreted my post that way. I have great respect for the expertise and clarity of explanation you demonstrate in every post I’ve seen.
The poster I quoted, threemae, was making the general observation that the SDMB has a lot of expertise in amazingly diverse areas, incidentally including electrical plant engineering, the topic of this particular thread.
I seconded that motion, while offering a corresponding lament that there are also a lot of non-experts who don’t realize where their expertise fades from real knowledge to assumptions and “common sense”, to speculation, even to downright fantasy. And that, human nature being what it is, those folks often are among the first to jump into the fray with authoritative sounding posts.
It was meant as a general comment about the overall SDMB GQ and IMHO experience. Again I apologize if my post appeared to be aimed in your direction. It wasn’t meant that way at all.
Won’t somebody please think of the light bulbs?
Fair enough. No hard feelings. Your post gave the the impression that you felt that this particular OP wasn’t answered until Una showed up. You can see how one could make that interpretation, but no matter. 
I am glad I was not the only poster who felt slightly slighted by LSLGuy’s comment.
All one, all one! Dilute! Dilute!
Though the OP has been answered, when I saw the thread title I thought it sounded like a mutation of the canard that turning off and on your lights used more power than to simply leave them running all night, that somehow you would “save power” by leaving them on. It was one of the first questions I asked on the SDMB, even. (A discussion of the answer can be found in the thread, but as it is two years old, it oughtn’t be bumped.)