Does it save energy to leave the lights on or turn them off?

You are right, your friend is wrong. This is one of those myths that people who are uneducated about science think could be true, and they pass it on without even checking it. It's absolutely false: turning the light off always saves energy. It's a light bulb, all it does it complete a circuit. It's not a train. There is no huge energy burst required to turn the thing on.

The only issue with the energy saving bulbs is that turning them on and off repeatedly can reduce their life. But it does not cause them to use more energy.

I work at a center that teaches about electricity. We do several experiments with light bulbs and use watt meters. It is true that a CFL uses a little bit more electricity when it is first turned on, but it is a very small amount. A 15 watt CFl will use about 15.4 watts for about 10 seconds before it goes down to 15 watts. Some CFL's take a few seconds to "warm up" or come to full brightness and turning them off and on frequently can reduce their life. I have a CFL in my laundry room which is one of the rooms that the light gets turned on and off frequently and I haven't replaced it in over 5 years. Make sure you get and energy star bulb to ensure quality and long life.

So, you are right, you save energy by turning off the lights when not in use.

You save energy by turning the lights off anytime you are not using it (particularly at those times when you are away). Turning the lights on and off may shorten the lifespan of your bulb by only a bit. However, the cost of replacing your bulb will be much much lower than the cost you will incur if you keep leaving your lights on all the time.

What your room mate said was true 50 years ago when the starter systems used a lot of power. That is no longer true.

The down side is the fact that frequent on/off cycles can greatly shorten the life of the bulb, so it is economically bad to turn them on and off at short intervals, not so much because of the energy waste, but due to the other economic wastes.

Don't forget, it takes a lot of energy to manufacture those bulbs.

I wonder about that, too. You've seen how the Compact Fluorescent bulb

starts out dimly, having to warm up to full output. Of course the office-style

fluorescent tubes have "instant-on", and they use 40 Watts per tube plus

the ballast uses up some wattage. Ever see whole office buildings with

ALL the lights on all night?

I think our little miser lights could stay on for a year and use up not too

much energy, compared to my 2 A/C units in Summer in Phoenix, trying

to keep 2 floors down to 78F.

no she is not right.i guess that u r right on ur part.if it would not have been the energy saving type bulbs then yes of course there will be a wastage of electricity.but u have the energy saving type of bulbs so there is no problem in that,but still it is better to switch off the light bulbs before u get more electricity bills.switching off the bulbs at certain times when not in use reduces the amount of bills.so u r right and ur friend is wrong.

i can't answer on modern-day lights furniture, yet i will permit you recognize that is not any longer genuine that previous lights furniture took greater power biking on and off. the priority with biking on and off isn't power used yet shortening the existence of the bulbs turning them on and off for all time. If bulbs have been unfastened, and power have been the sole project, the lights furniture might turn off the instant the final individual left the room for a minute. to save 5 cents of electrical energy is mindless in case you burn out a bulb that expenses a number of funds and in a paid environment could additionally value particularly some funds for somebody with a ladder to return and alter it.

this has already been busted

"Episode 69: 22,000 foot fall, Lights On or Off

* An explosion can save you from a 22,000 ft fall: busted

* It's better to leave light bulbs on: busted"

http://kwc.org/mythbusters/2006/12/episode_69_2200...

the value calculated was 23 seconds. A flurescent light bulb (the tube type, for a worst case scenario) running for 23 seconds uses up the same amount of electricity as one that starts up

it doesn't save any energy to keep the lights on

light