JRS: In article , dated Sat, 27 Aug
2005 22:27:12, seen in news:uk.transport.london, Nick Cooper
posted :

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.

I can believe the first five words.

In fact I can believe what you write after that; but not what I suspect
someone, if correctly quoted, meant by it.

Power is rate-of-energy, corresponding to the speed of an electricity
meter. Energy is basically what one pays for.

I can easily believe that the start-up current, and hence the start-up
power, exceed the continuously-running value; though I do not assert it
to be so.

But starting takes seconds only; so if it used more energy than running
for hours, which is 3600 times longer, then it would draw about 3600
times the current. The best typical modern fluorescent draws about 10 W
running, say 40 mA; 3600 times that is 144 A. The full rating of a
small domestic installation is of the order of 100 A. The main fuse
might survive; the local one would not. Thus it cannot be so.


The other consideration for expense is tube-life; it's reasonable to
believe that turn on/off wears the tube out as much as a rather long
period of steady running. And tube-life matters not just for tube-cost
but costs of fitting a new tube to replace an old one.

--
© John Stockton, Surrey, UK. / ©
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