Halogen light energy efficiency

Are halogen lights better than regular incandescent lights?

Can you tell me more about halogen light energy efficiency? My builder is telling me we should have halogen lights in our rec room reno but I believe that may not be the most efficient choice. I’ve heard that halogen lights are more efficient than regular incandescent lights. Is this true? And how do halogen lights compare to other energy efficient options such as fluorescent lights and LEDs?

Answer from Green Energy Efficient Homes

Most people are pretty misinformed about halogen light energy efficiency, assuming, as your builder does, that halogen lights are far more efficient than incandescent lights. There are a couple of issues to clear up here. First of all, halogen lights aren’t a different type of light from incandescent lights; they are one form of incandescent light. Secondly, it is challenging to compare the light output for different types of lights, and manufacturers often take advantage of this challenge to make misleading claims about halogen light energy efficiency as well as the efficiency of LED lights.

Incandescent vs halogen lights

An incandescent light is a type of light where a metal filament (usually tungsten) is heated up by having electricity pass through it, causing it to heat up so hot that it photoluminesces (emits light, much the same way molten hot metal or your stove element on high turns a bright red). Both regular incandescent bulbs and halogen bulbs operate in this way.

The filament for an incandescent light operates in a gas mixture encased in glass; that gas often consists of a mixture of argon, nitrogen, and nonreactive gases. In a typical screw-in halogen bulb the real bulb is actually much smaller than the screw in bulb you can touch; if you look carefully you can see a very small bulb in the middle, within the glass bulb. It is this inner bulb that contains a halogen gas – a gas in the halogen family, such as fluorine or chlorine – rather than nitrogen or argon. The inner bulb is made of quartz rather than ordinary glass, because the filament in a halogen bulb gets much hotter than a regular incandescent bulb, and this heat would cause ordinary glass to simply melt. Some types of halogen bulb only consist of that inner bulb, which is why when you handle such a bulb you have to be careful not to touch the bulb itself with your fingers: oils or sweat from your skin can dirty the bulb, and when it gets very hot these oils or moisture can cause the bulb to crack.

Halogen lights are preferred by many to regular incandescent light bulbs not because halogen light energy efficiency is better but because they tend to last longer than incandescent bulbs. Incandescent bulbs have among the lowest life expectencies of any light bulb: you can get around 500-800 hours of use from most incandescent bulbs. Halogen light bulbs are typically rated for about twice that long.

Measuring lightbulb output

The usual measure of light output for any lightbulb is lumens, and halogen light energy efficiency is typically measured as lumens per watt, or the number of lumens the light shines on a particular spot, divided by the wattage of the bulb. The trouble is that different bulb types have different light distribution characteristics. Incandescent bulbs typically distribute light quite broadly, because the light emitted from the tungsten filament goes in every possible direction. Halogen light energy efficiency typically seems higher from a lumens/watt perspective not because the filament emits more light, but because most halogen light bulbs contain a reflector that redirects much of the light out the end of the bulb. That’s why halogen lights are chiefly used in ceiling pot lights or flood lights: because the reflector sends all the light in a fairly focused beam, straight down to the space under the light.

Imagine if you were to place a light meter four feet underneath a light bulb. The light meter will give you a reading of how much light is shining on the meter. If the light bulb casts a broad light, such as is typical of a regular incandescent light bulb, the portion of the bulb’s light that strikes the light meter will be pretty low. But if the bulb produces a focused beam and the light shines straight down onto the meter, you’ll get a much higher reading on the light meter. Halogen light energy efficiency seems higher than incandescent light efficiency exactly because halogen lights are usually designed for these highly focused applications, resulting in higher light output at the point where the measurement is taken.

If you only want light directly under the light bulb, it’s perfectly legitimate to measure light this way. The trouble is that most home renos these days don’t take account of the halogen light energy efficiency that makes these lights so wasteful. For example, you can put two 60-watt incandescent bulbs in a ceiling light fixture and light up an entire 10×10 foot room very brightly. But try putting two 60 watt halogen bulbs in pot lights in the same room. The light will be very, very bright directly under each of the bulbs, but the far corners will be in deep shadow. We overcome this by sticking in 4, or 6, or even 9 halogen lights to get rid of these deep shadows. The result is that the room feels nice and bright, and our energy use is about 2 to 5 times greater than with incandescent light bulbs.

Theoretically, halogen light energy efficiency should be slightly higher than regular incandescent light efficiency: you should get roughly 16 to 24 lumens per watt for halogen, while a regular incandescent light should get between 12 and 18 lumens per watt. In practice halogen light energy efficiency as measured is only marginally better than that of incandescents. The table below shows the wattage and lumens output of a large number of light bulbs available on Amazon. (I’ve tried to stick to light bulbs that get higher than average customer reviews, so you don’t accidentally buy a piece of junk should you click on one of the links!) I’ve sorted them from least to most efficient in terms of their lumens output per watt.

Some points to make about the table:

• Regular incandescent light efficiency should in theory be lower than halogen light energy efficiency, but only one of the halogen light energy efficiency ratings is higher than the average of the incandescent ratings.
• CFL or compact fluorescent lights are significantly more efficient than either regular incandescent or halogen incandescent lights. Dollar for dollar, these really are the best investment, as CFL prices have come a long way down in the last couple of years and they produces 3-4 times as much light output per unit of energy input as halogen or incandescent bulbs. CFL lights tend to have a very wide light distribution similar to regular incandescent bulbs.
• LED house lights have a similar light distribution to halogen lights – very focused – so you can compare the rated lumens for LED lights to halogen light energy efficiency. One thing that quite surprised me was that the LED lights were on average no better than the CFL lights in terms of lumens of light output per watt. The rule of thumb typically used is that CFL lights are 3 times more efficient than incandescent lights, while LED lights are 10 times more efficient. It seems that LED lights have a long way to go still, since all of these LED bulbs are only marginally better than the CFL bulbs.

Wattage and lumens output of selected light bulbs

So to answer your question about halogen light energy efficiency, halogen bulbs really aren’t much better than regular incandescent bulbs. If you want to get a more energy efficient bulb, while having the same warm white color and bright, focused look of regular halogen spot lights, you may want to look at LED pot lights as one option, but I still feel LED lights are not quite ready for wide adoption. A better choice from an energy efficiency would be compact fluorescent lights, if you can find ones that produce the warm white color most people prefer. In any case, you now have what you need to talk your builder out of his misunderstanding. Halogen light energy efficiency isn’t really any better than incandescent light efficiency, and the best way to save energy on your lighting is not to use too much of it!