Are compact fluorescents always more energy efficient?

Question

I have been told that compact fluorescents use more power before reaching its optimal operating temperature, so if you have it in areas where the light are turned on and off frequently instead of kept running, it could actually cost you more because this takes away from the overall life of the bulb. But does anyone know how much energy the bulb uses before reaching its optimal operating temp?

And also, what are some other cases where compact fluorescents would not be efficient?

Answer 1

I think this is a good question.

It is a statement which is true, yet deceiving at the same time,

because "more power" could mean two different things.

Most people think that this means more power than an equivalently rated incandescent light bulb. It does not.

It does use a bit more power during the warm up period than it does when it is operating at full efficiency, but not more power than it's equivalent incandescent relative.

The amount, and length of time it takes are so insignificant, that it is not really worth mentioning.

The same statement could be used for every electrical item I can think of right now including incandescent lights.

For instance, a 60 watt light bulb will use 250 watts or so when first switched on. This is only for a few milliseconds, but the filament starts out at a very low resistance and has to heat to incandescence for useful light to be produced. As the filament warms it's resistance increases and then draws less current.

The same is true for all fluorescent lights not just CFL's(compact fluorescent light).

This warm up period for full efficiency depends mainly on the ambient temperature in which they are operating, the colder the temperature the longer it will take.

That isn't to say however that they are not more efficient for lighting purposes as compared to an incandescent light no matter how they are used.

I personally think there are actually 3 stages to reach full efficiency.

Each stage is dependent on things like the age of the device, the manufacturer of the device,etc...

There have been major improvements over the last couple of years, and all manufacturers are not equal in their approach at any specific time. It would be wrong for me to say which one is best right now because they are all improving. One manufacturer which I thought was the worst two years ago is now one of the better, if not the best.

The three steps are:

1)Power up.( The time it takes the filaments at both ends of the tube to heat up and the high voltage potential across the tube to build up sufficiently for the gas inside to be ionized and effectively conduct.

This is the period of time when most energy is required.

In a house at normal room temperature (70-72F or 21C), the warm up period with early makes ranged from between half a second and two seconds or so.

Today, it is only milliseconds.

2)Initial warm up.

At this point two things are happening simultaneously.

The high voltage circuitry is adjusting itself for maximum efficiency, and (in the latest units I've seen) reducing the filament voltage which is no longer needed for ionization to occur.

This also is when the phosphorous coating on the inside of the tube is being excited enough to convert the ultraviolet light from the ionization of the gas into useful visible light.

Depending on the manufacturer and design of the unit this period of time is usually 3 to 10 seconds.

3)Full stability and output.

To reach this point from step 2 takes between 10 and 30 seconds.

To put this into useful context let's use an example of an 18 watt CFL that has equivalent light output as a 100 watt incandescent.

Step1) 35-60 watts for a few milliseconds with newer units.

Step2) Reducing from Step 1's original state to 25-30 watts for 3-10 seconds

Step3) Reducing from step 2's state down to 18 watts taking another 10-30 seconds.

So to reach total efficiency may range from 13 seconds up to about 45 seconds.

However you will notice that at no time does it ever use more power than an incandescent would use.

Now if your still with me, (I know it is a bit long-winded) I would like to mention a couple of other points which I feel are relevant, and need addressing.

I can see where Michael is coming from, the same is true with incandescent lights also. The more they are turned on and off the shorter their lifespan.

With CFL's the problem is even far greater in that you don't just have just one filament which will eventually fail but two, doubling the chance of premature failure by continuous stress, but there are over 20 other electronic components on the circuit board which are susceptible to failure.

So switching off a light and back on several times a day will lead to early failure.

You would have to decide for yourself whether this is acceptable or not.

Factors to consider are the amount of money you are saving by switching it off, how long the unit has been in service and whether it has already paid back it's original investment, and how much a replacement will cost.

I can see that Marc has been scared by the latest 'Health and Safety' c**p.

Bob is correct about the extremely minute amount of mercury which is in CFL's (my understanding is it's even less than half of Bob's figure).

What most people fail to understand is that mercury as an element is completely safe anyway.

It is only long term exposure to the oxides formed by mercury, and in extremely high concentrations, that it could lead to physiological damage.(Something the so-called experts can't even grasp)

Also the fact that we have been using fluorescent lighting for well over 60 years now and over 60 million of these (each having between 10 to 80 times more mercury than a CFL) have  been disposed of over the years without causing any ill effects whatsoever.

Fluorescent lighting has always been more efficient due to the lack of wasted heat produced.

I have wondered for sometime however in some cases where the trade off actually can be realized.

For example:

When the weather is cold. Is that really wasted energy?

The energy that is considered as wasted heat because it is not used for the purpose it was intended for is being released into the room. This in turn should reduce your energy consumption required to heat your house.

Yet on the other hand, when the weather is warm, you do not want excess heat being produced, and may use more energy to extract that excess heat.(To me these are simple ideas which nobody ever considers).

I hope this helps.

Answer 2

I hope others in the lighting industry aren't as ignorant as Michaell.

It is more efficient to turn them off when they are not in use.

Answer 3

CFL's contain trace amounts of mercury so if one breaks in your house you and everyone in the house are subjected to mercury fumes which are extremely hazardous. When you go to dispose of them they need to go to a hazardous waste site. I know this does not answer your question but I thought you might want some of the facts that are not so well known about these so called environmentally friendly lights. They don't work well in below 40 degree temp.s due to problems reaching operating temp.s and the lower the temp.the worse they are and at a low enough temp. they won't work at all.

Answer 4

The energy it uses is still way less than an incandescent bulb.

You can shorten its' life by turning it on and off very frequently, but it's hard to see where you'd be doing that.  It has to be VERY frequently.

As far as mercury goes...

Using compact fluorescent lights (CFLs) actually reduces mercury pollution.

Fossil fuels contain mercury.  Using incandescent bulbs causes more mercury to be emitted from power plants.  More than the tiny amount (0.005 grams or less) that is in a CFL.

It's better if you dispose of old CFLs properly (they don't have to go to a hazardous waste sire, and many communities collect them) so that even the tiny amount of mercury is not released.  But, no matter how they're disposed of, CFLs reduce mercury pollution.

http://www.cityofberkeley.info/sustainab...

http://www.snopes.com/medical/toxins/cfl...

Answer 5

COMPACT FLUORESCENTS ARE MORE ENERGY EFFICIENT HOWEVER IF THEY ARE TO BE TURNED ON AND OFF EVERY 20 SECONDS THEN YES IT IS BEST TO LEAVE THEM ON, THE ONLY SPIKE THEY HAVE IS WHEN JUST POWERED ON AND THAT IS SUCH A FAST SPIKE YOU SHOULDN'T BLINK IF YOU ARE READING IT ON A TESTER.  THE BEST LIGHT TO USE IS LED LIGHTING THEY ARE MORE EFFICIENT THAN THE FLUORESCENTS BUT COST MORE.  

IN ANYCASE IT IS ALWAYS BEST TO TURN YOUR LIGHTS OFF WHEN YOU ARE NOT IN THE ROOM :)

Answer 6

my name is michael i own  a lighting company.  they are 15-80% more efficiant then a standard bulb. yes you should just leave them on rather then turning them on and off all day. hope that helps if not e mail me [e-mail]