Truth: Start-Up Power is Negligible
Like a car that needs a shot of gas when you start it, all lights draw a spike of current when they turn on in order to heat up a cold filament in an incandescent or to excite the gases used in fluorescents. But the start-up power lasts only for an instant, so the effect is negligible compared with the lamp's ongoing usage. If you turn off a fluorescent lamp for even an extra half hour a day, you can save about $4 over its life—enough to buy a replacement bulb. Frequent on-off cycles do cut down on the number of hours a lamp will light, but since it isn't being used as much, the lamp still lasts longer.