Light Sources: Halogen Explained

A close cousin of the incandescent light bulb, halogen light works by burning a tungsten coil in a vacuum filled with a gas such as iodine or bromine. Because of a chemical reaction in the gas, burnt tungsten gets redeposited onto the filament coil, enabling it to burn brighter while consuming less electricity and lasting longer. 

There is one important distinction to be made within the halogen family: There are line voltage halogen sources and low voltage sources. Line voltage is a fancy way of saying, “the voltage coming out of your wall outlets” in the US, that means between 110-120v. 

Like common incandescent lamps, halogen A-lamp replacements can be plugged into sockets connected to line voltage. You will see low-voltage halogen sources in stores. Low-voltage sources require a step down from line voltage to their native 12v or 24v. When replacing incandescent light bulbs, it’s line voltage halogen we’re looking for. They will have a similar size and shape to incandescent bulbs and will always include a medium screw base, just like the common light bulb. 

Brightness - Halogen replacement bulbs are meant to mimic the light outputs of their incandescent cousins, and they do so while burning about 25 percent less energy. 

Color - Halogen light sources generally burn a slightly cooler white than incandescent, though the difference is tough to notice, especially at lower wattages. 

CRI- Halogen light sources are generally stamped with a 100 CRI rating, so for many applications where display of color is important, halogen sources are helpful. Halogen A-Lamp replacements also dim exactly as incandescent sources do using the same dimming technology. 

When looking for halogen replacement bulbs, consider three things:

• Look for “BT15” in the part number to ensure proper size. 
• Look for “white” finish to ensure softness of the light. 
• Remember a 75W halogen will be much brighter than a 75W incandescent bulb.

Recommended Applications:

• Recessed downlights, where color rendering is critical, especially in bathrooms. 
• Decorative fixtures, where the bulb might be directly visible. 
• Any place where a smooth dimming and/or incandescent feel are critical. 

Halogen is the most energy intensive of the common alternative light sources allowed under the new law. When used in high-importance applications, it can be very useful. Halogen not only works well as an incandescent replacement in table/floor lamps and recessed fixtures, but its low-voltage version has hundreds of design uses. Low-voltage halogen is found in sources meant to throw light in definite directions with a channeled beam. Sources like these are often essential to great lighting, and for the moment, no lighting technology does it better than halogen.