Zyra's front page //// Misconceptions //// Lighting //// site index

Zyra doing weird experimentsThe excessive amount of electricity initially used by

Fluorescent Lamps

when you switch them on


NOW, THe thING About FLUOrescent LAMPS IS THAT WHEN YOU SWITCH THEM ON THERE IS A SUDDEN INITIAL SURGE OF ELECTRICITY.

The folklore on this is that a fluorescent lamp uses more electricity when you turn it on than during ten minutes of normal operation.

This is NOT TRUE! There is an initial surge, but it is nothing like as big as that. Thirty seconds would be more realistic. This can be proved by various methods, according to whether you prefer theory or practice.

The practical approach is to watch an electricity meter while someone else turns on a lamp on cue. If you've got one of these eddy-current meters with a wheel that goes round in plain sight, you'll see it have a quick spin as the light goes on. By consideration of how many rotations the wheel makes per unit of electricity you can get this in proportion. Also, see how long it takes the wheel to go around as far in normal operation as it did for the initial burst. For example, when the lamp goes on the wheel might go round half a rotation, but then in the next thirty seconds it will go round another half a rotation.

The other way is the theoretical approach. Supposing a fluorescent lamp used as much energy in the first three seconds as it did in the next ten minutes, that would mean that for those three seconds it would use the same power as 60x10/3=200 lamps. As the lighting circuit is rated at 5 amps, don't you think the fuse would blow?!

So, don't worry about fluorescent lamps using too much energy as they start up. The initial start-up burst is there, but it's not big. Plus, the fluorescent lamps are cheaper to run than filament bulbs.

Other notes:

Other approximately relevant items: Voltage and Current, electricity price comparison, lighting

Did you know? Lamp Shop Online is one of the lighting suppliers specialising in fluorescent lamps? That and LED tubes.