Nick Cooper (and similarly Neil Williams) writes:
I am not an electrician, but... someone told me that actually
switching on fluorescent lighting uses more power than leaving it
running for quite a number of hours.

They were wrong. For "hours", you should read "seconds". This
should be obvious if you think about the wattage rating of the
lights, and the fact that turning them on doesn't overload the
circuits.

However, almost any type of electrical equipment tends to have a
shorter life if switched on and off frequently. (People who know
what they're talking about typically recommend that lights in a
home or office should be left on if they'll be needed again a few
minutes later.)

Also, sometimes when a fluorescent light is near failure, it will
stay lit once it gets started, but needs a minute or two of warmup
before it will start -- and because it draws more power during
startup, other lights on the same circuit may also fail to start.
quickly. Turning them off then makes this failure mode possible
when they're turned back on.
--
Mark Brader I "need to know" *everything*! How else
Toronto can I judge whether I need to know it?
-- Lynn & Jay: YES, PRIME MINISTER

My text in this article is in the public domain.