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Friday 26th August 2016
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Do fluorescent lights use more power when turned on?


flourescent strip lightWhen I had a big fluorescent strip light installed, I was told not to turn it off, as the electricity it uses to switch on is as much as leaving it on for ages. What is the equivalent number of hours of use it uses?
Rick, Whetstone


** Definitive **
Name: Christian, Hertford
Qualification: Lighting controls engineer
Answer: It works on a hot cathode principle. You have a strip of mercury, and the tube is filled with a gas. You need a big jolt of electricity to heat up that mercury. Nowadays, they are quite efficient, so they don't need much power, but 40-years-ago, they would need a lot of electricity. It depends on how old the capacitor is. But even with the old ones, it only takes about as much electricity as 20 minutes of lighting.

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