Energy Conservation (question)

[RigaMortus2]

So in the spirit of Earth Day, my fiance and I were discussing what takes more energy, turning on a light or keeping it on? I have always heard that it takes more energy to turn on a light than it does to keep it on. Is this just an urban myth? And if it is not, sure there is some point when keeping the light on WILL consume more energy than it would to turn it off and then back on when you need it.

If anyone knows the true answer, and more importantly, can point me to some articles (my Google-fu is not working), I would highly appreciate it!

BTW... This question can be asked of any electric appliance, TV, radio, computer, etc. I just always used the "light bulb" as the subject of my question. Would the appliance matter? Does it take more energy to turn on a TV set than it does to leave it on?

 

[Pbartender]

Is this just an urban myth?

Yes.

Turn electrical devices on and off does not consume more energy than leaving them on, however... Many devices will lose a considerable portion of their lifetime by frequent turning on/off. Flourescent lights, for example, can lose up to 5-10% of their tube life. This why many large offices leave lights on all night -- it's cheaper to pay for the extra energy than it is to pay for someone to replace the tubes more often. It's also the primary reason why many people recommend not shutting computers off -- it can be hard on the hardware.

Incandescent bulb lifetimes, on the other hand, are almost entirely unaffected.

Older fluorescent lights do in fact require an initial burst of energy to turn on. However, the energy required is small and the savings from having the lights off more than compensates in a matter of seconds. Standard incandescent lights use absolutely no energy in starting so the bottom line is, turn off the lights to save energy.

The same goes for any other appliance.

If you want to really conserve energy, you're far better off buying more efficent appliances. Switching, for example, from incandescent bulbs to flourescents, wherever possible, and choosing the most energy efficient refrigerators, washers, dryers, etc... The big appliances typically account for the majority of your home electric bill.

 

[physicscarp]

Pbartender is correct.

The Mythbusters did a show on this very myth and they busted it.

 

[RigaMortus2]

As they said, myth busted! Thanks guys.

 

[Ferret]

On a similar note, a friend tells me its better to leave a computer on then turn it off. They say that it takes more energy to tun it off than to leave it on all day. Which I don't believe!

 

[moritheil]

On a similar note, a friend tells me its better to leave a computer on then turn it off. They say that it takes more energy to tun it off than to leave it on all day. Which I don't believe!

That's a hard drive life issue, not an energy saving issue. I don't even know if it's still valid, since some HDs may have been redesigned to avoid that issue.

 

[Hypersmurf]

If you want to really conserve energy, you're far better off buying more efficent appliances. Switching, for example, from incandescent bulbs to flourescents, wherever possible...

When I was in Standard VI (Uh... 7th grade, I think?), our Science teacher was a Franciscan monk.

He used to lament that he was about the only scientifically-inclined Brother at his monastery. He simply hadn't been able to get it through anyone else's head that switching off the nice bright 15-watt fluorescent light in favour of the little dim 25-watt incandescent bulb in the corner not only made it impossible to see anything, but also used more power...

-Hyp.