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Turning off lights - times

Incandescent lights: Turn off whenever you leave a room.
Compact fluorescents: Turn off if they will be off 5 minutes or longer
Fluorescent lights: Turn off if they will be off 15 minutes or longer

According to the U.S.
Department of Energy, incandescent lights should be turned off whenever
you leave a room. For fluorescent lights, generally they should be
turned off if you are going to be leaving a room 15 minutes or longer,
otherwise they can be left on. For more information:


I read recently (past 6 months) in a respectable source, that the
fluorescents now-a-days do not consume a lot of energy to "excite the
electrons" and that the 15 minute rule is obsolete - replace with a 1-2
minute rule (which means to me, turn them off!).

This is actually more complicated than pure energy
conservation. It's true that fluorescent bulbs are different today - I
think it is the ballasts that are more efficient - but turning them on and
off shortens the life of the bulb. It will save electricity to turn them
off, but the Department of Energy says it saves money if you follow the 15
minute rule. There is the additional concern about energy and resource use
in producing bulbs and pollution concerns in disposing of them, so I
decided to go with their recommendation.