Fluorescent light startup energy demand

I’ve heard from many people in my life that the energy needed to start a fluorescent tube light is the same as the energy required to run it for several hours (up to 17 hours, I was told). Therefore turning them off only to turn them on again after a few minutes uses more power than leaving them on all day.

I’ve look on the internet to try to find some evidence or figures but I can’t.

Do you know if it’s true or have any figures for the actual time you need to leave them on to make savings?

Leaving the lights on “to save power” is nothing more than foolishness being propagated by the ignorant I’m afraid…

Fluorescent tubes use 23 seconds worth of power at startup…
Compact fluorescents use 0.015 seconds worth of power at startup…
Regular incandescent bulbs use 0.3 seconds worth of power at startup…


Basic knowledge of physics is enough to debunk this myth. If the lights drew that amount of power in a short time, then the current would be so great as to blow the fuse.


Cool link

the second question they tackle is whether regularly turning on/off the bulbs will affect the life of the bulb (ie affecting replacement cost). Although it sounds like, in the context of “normal residential use”, they believe the impact is nominal, a poster on this site had this to say:

treehugger.com/files/2008/04 … ed-cfl.php

(But take it with a grain of salt, not sure what he’s basing his conclusion on)

Right now, I’m using Megaman compact fluorescents that fit into the regular incandescent fixtures.

Anyone have any suggestions on what they use?

You can talk to any convenience store manager who has been there a long time for their experience in life cycle of a florescent light left on all the time (at work) versus ones that has been power cycled all the time (at home or in the back room). They should have a clearer answer for this since those stores open 24 hours a day therefore the light in the store has to be on at all times.

I went looking for my local convenience store manager but all I found was a blackened wrinkled ape like creature with 2 inch thick glasses, could that be him/her?

By coincidence, I was reading a book on home wiring which had much to say about this.

In short, it’s better to turn the lights off when you’re not in the room.

BUT (there’s always a “but”), there are two types of fluorescent bulbs (with starters to match), and there is a difference in the life expectancy of the bulbs depending on how often your turn them on/off. They also differ in how much power they use after being turned on.

  1. The “instant on” type of fluorescent tubes use a lot of power to start, and the sudden surge of power reduces the life-expectancy of the bulb. By way of compensation, if you leave the lights on for a long time, they use less power.

  2. The “slow start” type of fluorescent tubes use much less power to start, but they use more power just to remain lit. If you frequently turn the lights on/off, this would be the type to use. But if you leave the lights on for many hours/day, go with number 1 above.