Is leaving your lights on more economical than truning on and off your lights several times a day?

Question

I'm trying to find some answers on this subject for my boss. Can anyone shed some light on this subject for me? Tell me were I could possibly find more information?

Answer 1

That is a very popular belief. It even made it to the Mythbusters.

Data collected from ;lights turned on and off or those left left on at all times shows no significant difference in power consumption.

It is also more of a common sense. The power used by lights when turned on is very miniscule compared to what you save when you turn it off for several hours.

Answer 2

It depends on the light.  Fluorescent work better and last longer if you leave them on.

Answer 3

Huh?  No way!  Where on earth did you hear THAT one?

Answer 4

The answer depends on the type of light, and the amount of on vs off time.  And the on duty cycle.

Incandescent bulbs have a large starting surge, because the electrical resistance of cold tungsten is about 1/10th of the hot operating resistance.

Very large tungsten filament devices have to be step-started or the inrush current will tear the filaments apart.

Smaller bulbs are not that destructive but for a short period of time pull a lot of energy used merely to heat the filament to glowing; after that, the higher resistance consumes less electricity.  However, the inrush current does slowly damage the filaments and each on-off cycle reduces the overall life.

Metal (and carbon) bulbs which are never exposed to voltage surges, and are left on continuously last much longer than those which  are subject to frequent on-off cycles.

There is a balance to be struck between power consumed AND shortened life in turning metal-filament bulbs off when not in use, and then back on, and the energy consumed by leaving the bulb on continuously, some of which may be wasted by nobody needing it.

In general, if you need light most of the day, turning the bulb off when you leave your desk for the water cooler, or lunch  does more damage in terms of reduced bulb life and replacement costs, including labor, than leaving it on.

At the other end, if you work 9-5, and are then off 5PM to 9AM, turning the lamp off while you are not using it at night is more economical.

The  LED lights are quite efficient, since their light is all emitted in a narrow band, even tho the electrical conversion is not terribly efficient.  But they also use very little electricity in making heat, contrary to the incandescent bulbs.

And they last 10's and hundreds of thousands of hours, so little replacement needed for years and years.

However, for major general purpose lighting they are far too expensive to buy...very high initial costs.

There is no turn-on-turn-off penalty, and for specific coloured applications, they are far better if the high initial cost can be balanced by the tremendous life.  "White" LEDs are becoming available, but are still high in price, tho the colour is good and can be tailored to the exact shade desired...warm, cold, complexion-enhancing, etc.

Gas discharge lamps are like Incandescent, a high starting surge when initially lit, and then lower current to keep the gases glowing,  They generate more heat than LEDs and generally require high voltage transformers.

But they are far more efficient when lit.

The metal vapor lamps are very efficient, but again have high starting surges, and some cannot be safely turned on and off rapidly.  They also are hot in operation.  Best for long term lighting as in outdoor night uses.

Flourescents have a starting surge, usually lower than incandescents, and are very efficient in energy consumption.

Then can be turned on and off fairly often, at low energy penalty, but will have shorter life too.  Not as bad as incandescents however.  

They require special ancillary components, often heavy, called "ballasts" to stabilize the operation.  Their life is much longer than incandescents, so the somewhat greater expense of the lamp and the socketing is generally more than offset in lower electric costs and lower maintenance costs..  

They in general when worn out present a bad pollution and health hazard because of dangerous materials, such as mercury and beryllium used in the tube.

So...the answer is, it depends, on what type you use, and how your budget is for purchase and replacement.  The general answer tho is for a few minutes, leave it on...for long time, perhaps more than an hour depending on your electric rates, turn it off and back on.

Generally, you can write the manufacturer and get this information.  Direct the question to customer service, and specify the bulbs to be used, as to power level and fixture voltage.

The old TV camera lighting 10,000 watt bulbs were better turned off for any time over 5 minutes based on power, and especially if you brought them up on a dimmer so the filaments never got strained!!  And because of the immense heat they gave off...one of the considerations of the incandescent bulbs...lots of their energy goes into heat.

Answer 5

A very good question.  Turning on your lights (especially incandescent ones) shortens the life of the filament.  If you include the cost of the bulbs, it might be cheaper to leave them on.

Answer 6

Myth busters did a show on this. It does not save money leaving them on - that includes all types of bulbs. The life span is a minimal factor when you compare bulb price to electricity cost.

Answer 7

by far not !

Look at when you press the switch... how many seconds does it take to bring the bulb to the energy level to be operational ?

1 sec ? Ok... then compare it with one hour running.. 3600 sec

Does that give you an idea ? The energy used to restart the radiating process in neglectable

Answer 8

I believe this idea used to stem from the fact that when traditional bulbs were turned off an on it caused the filaments a lot of stress and energy to turn on, and due to the inexperience in manufacturing, this caused a lot of waste in terms of the amount of light bulbs one had to use per year.  With the new halogen bulbs, these fears do not exist, and they use more than a tenth less energy.  For this reason, I turn my lights on and off, leaving them on uses energy, turning them off conserves energy lowering your electricity bill and is thus more economical.

Answer 9

the initial surge when turnig a light on does use more electricity but only for a micro second, compared with constant use witch will use considerably more

Answer 10

Leaving your lights off when you are not using them is the best bet.  It is true that the process of turning lights on/off creates a surge and may lower the life of the bulb.  It is however, more cost effective and saves more energy to leave them off when not in use.  Check out www.energystar.gov for more information

Answer 11

The energy used turning a light on, even a fluorescent is very small compared to that used when it is on while no one is in the room.

When leaving a room, turn the lights off if you want to save energy.

Answer 12

depends how often and what type of lights, but generally speaking yes.

Answer 13

They tested this on Mythbusters!

They figured out that it's definitely not better to leave the lights on all day then to turn them off several times.  I think they calculated that the only time it would be more conservative to leave the lights on instead of turning them off would be in such a small instance that there would barley be enough time for a person to fully enter a room.  

So, turning the lights off is definitely better.

Light pollution sucks for star gazers!  Keep the lights low! You can find information on stuff like that by searching for Light pollution.  

Otherwise, search the web for energy conservation...or maybe even see if you can find information about the episode of mythbusters I'm speaking of here...that would be very helpful.  Search for the Discovery Channel online.