FunTrivia Homepage New Questions Unanswered Post a Question Goto Qn # Archives

# Is it cheaper to keep a flourescent tube light on rather than turning it on and off throughout the course of the day?

Question #80235. Asked by vixal. (May 11 07 5:43 AM)

car-crazy-alex

Yes, because it uses more energy to turn it on and off. That's why supermarkets leave their lights on throughout the night when nobody is inside the shop.

 May 11 07, 6:16 AM
worksafe

This is very similar to the myth during the 70's gas crunch that because it take more gas during starting a car engine then running that engine, you will save gas by leaving it running during stop stops such as quickly running into a store to buy a cup of coffee.

Consider that 30-40 watt fluorescent light needs 400 -650 volts for starting and 100 to 175 after starting, you can see that increased voltage during the few seconds of start up could be more cost effected than leaving the light on for all but an exceedingly short period of time. Factor in to this cost of replacing lights and ballasts more frequently and the cost will be much more if you leave the lights on.

Direct quote from http://www.newton.dep.anl.gov/askasci/eng99/eng99487.htm

The practical answer is, no, it makes no sense to leave a fluorescent light (of ANY type) on instead of turning it off.

This is an story that seems to have started over 50 years ago when someone noticed that the starting current for the first second or less, of a fluorescent lamp, was higher than its
current draw after that time.

Starting current of a typical fluorescent lamp is in the neighborhood of 50% more than its normal operating current. But as I stated above, this only lasts for around a second or
so. Even much less with many types of fluorescent lamps.

Let us take a standard 40 Watt fluorescent tube as an example.When you turn it on, it draws perhaps 60 Watts for the first second, then 40 Watts from then on. So, for the first second, it is using 20 Watts more than normal.

Now, let us say you are walking out of the room for just 10 minutes, and you decide to leave the lamp on, because someone claimed it would use less energy than if you turned it off, then on again 10 minutes later. That lamp will be wasting 40 Watts of electrical energy for 10 minutes, before you return to the room.

But if you switched it off, it would consume no power at all for that 10 minutes, then when switched back on, it would consume an extra 20 Watts or so for a mere second or less. So in this example, leaving it on would use "waste" 40 Watts for 10 minutes. Switching it off would "waste" 20 Watts for a second or less. Clearly, that old story about leaving fluorescent lamps running to save power is utter nonsense

 May 11 07, 7:32 AM
vixal

Excellent thanks

 May 11 07, 8:40 AM
Baloo55th

Supermarkets leave their lights on for security. Just as (round here, anyway) a house with lights visible is more likely to have its occupants out or away than if it looks totally dark. And can people please note that despite the presence of white powdery stuff when you break a tube, it is flUOrescent not flour, Wasn't there a question recently about commonly misspelt words? This is an easy one to do when typing quickly, however.

 May 11 07, 11:35 AM
MonkeyOnALeash

NO! In the distant past it WAS more economical to leave one running but with "todays" ballasts and bulbs this is not the case.

 May 11 07, 6:55 PM

 Sign up to see all responses! Create a Free ID instantly to see all recent responses, post your own follow-ups or questions, and access over 1,000,000 trivia questions! Choose a User Name: Your Email Address: Choose a Password: I agree by the terms outlined in FunTrivia's Conditions of Use

### Other Similar Questions & Answers

 Is it cheaper to stay cool by turning on the air conditioner, or to use a fan? Basically is the cooling of the AC or the electricity for the fan cheaper?

### Suggested Related FunTrivia Quizzes - 90,000 currently online

1 Light
 This quiz is a series of questions on reflection, refraction, lenses and spectrum... basically, on different areas of light.
Electromagnetic Spectrum and Optics Very Difficult
10 Q
Rossell
Feb 02 07
2505 plays
2 And Then There Was Light
 Visible light is a very small band within the electromagnetic spectrum. Physicists consider the entire spectrum to be light. How much do you know about light?
Electromagnetic Spectrum and Optics Average
10 Q
drbabe
Nov 20 10
453 plays
3 The Groove Tube
 What ever happened to Ken Shapiro, anyway? No matter - even if his only legacy is the bizarre 1974 cult comedy "The Groove Tube", he's still given us some great laughs! (Every so often, theaters will still run it at midnight.)
Gn - Gz Movies Tough
10 Q
astorian
Jan 06 04
156 plays

"Ask FunTrivia" is for entertainment purposes only, and answers offered are unverified and unchecked by FunTrivia. We cannot guarantee the accuracy or veracity of ANY statement posted. Feel free to post an updated response if you feel that an answer is inadequate or incorrect. Please thoroughly research items where accuracy is important to you using multiple reliable sources. By accessing our website, you agree to be bound by our terms of service.