Actually, lamp manufacturers generally rate fluorescent lamp life
based on three hour starts (3 hours on and 20 minutes off), in
accordance with IES LM-40-1987 testing standards.

Lamp life can be extended by increasing burn cycles but perhaps not as
much as you might expect. For example, a standard GE F32T8 has a
rated life of 20,000 hours based on 3 hours per start and a 24,000
hour life expectancy at 12 hours per start.

Source:
http://www.gelighting.com/na/busines...inear_fluo.pdf

A typical CFL would have a rated service life of anywhere from 6,000
to 15,000 hours, based on the aforementioned 3 hour testing cycle. By
comparison, a standard incandescent bulb has a rated life of just
1,000 hours.

A 100-watt incandescent bulb would consume approximately 100 kWh over
its normal life. At $0.10 per kWh, a consumer would expect to pay
$10.00 in electricity costs to operate this bulb. An equivalent
23-watt CFL would consume 23 kWh over this same timeframe, for a net
savings of $7.70.

A good quality, name brand CFL now costs as little as $2.00 to $3.00
when bought in multi-packs. Given that the cost of energy in the
manufacture and distribution of these bulbs would be a small fraction
of its retail price, even if a CFL were to fail at one-tenth its rated
life (i.e., 1,000 hours versus 10,000 hours), the value of energy it
would have saved would still exceed that of its purchase price.

In any event, I would expect a CFL with a rated life of 10,000 hours
to be capable of withstanding over 3,000 starts (i.e., 3 hours per
start x 3,333 starts = 9,999 hours). If you were to turn this CFL on
and off an average of ten times per day, it should (presumably)
continue to provide service for close to a full year.

If you turn lights on and off more frequently than this, you might
consider a "cold cathode" CFL. These CFLs can be turned on and off as
frequently as you wish, with no material impact on lamp life.

See:
http://www.tcpi.com/PDF/495_01116%20...Globe%20SS.pdf

Cheers,
Paul

On Thu, 14 Dec 2006 13:25:37 -0800, "# Fred #"
wrote:


I have the same issue with florescent lamps, and in particular with circle
line, and compact fluorescents. The rating on lamp life is based on
continuous burn hours but once you starts turning the fixtures on and off,
it will kill the fluorescents. Remember years ago before the energy crises,
you see floors all lit up 24/7 in high rise buildings - that is for
maintenance so they don't have to change out the lamps as often. My lamps,
like the ones in the hallways and bathrooms where its switched a lot, may
last only six months with a burn life of only 10 or so hours. So at some
point, incandescent lamps will be much more energy efficient than
fluorescents if you take the life-cycle energy cost into account including
the energy to manufacture the lamps.