Light Sources: Halogen Explained

This article explains how halogen A-Lamp replacements work.

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. 

I recommend frosted replacements with a BT15 code. 

I recommend frosted replacements with a BT15 code. 

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.