Incandescent light bulb: Encyclopedia II - Incandescent light bulb - Heat

Incandescent light bulb - Heat

Most incandescent light bulbs waste about 98% of the power they consume in heat.

An incandescent light bulb (about 2.1% efficiency) is about one quarter as efficient as a fluorescent lamp (about 8.2% efficiency), and produces about six times as much heat with the same amounts of light from both sources. One reason why incandescent lamps are unpopular in commercial spaces is because the heat output results in the need for more air conditioning in the summer. Incandescent lamps can usually be replaced by self-ballasted compact fluorescent light bulbs, which fit directly into standard sockets. This lets a 100 watt incandescent lamp be replaced by a 26 watt fluorescent bulb, while still producing the same amount of light.

Quality halogen incandescents are closer to 3.5% efficiency, which, although still extremely low, will allow a 60 watt bulb to provide nearly as much light as (and a 75 watt to provide even more than) a non-halogen 100 watt. However, small halogen lamps are often still high power, causing them to get extremely hot. This is both because the heat is more concentrated on the smaller bulb surface, and because the surface is closer to the filament. This high temperature is essential to their long life (see the section on halogen lamps above). Left unprotected, these can cause fires much more easily than a regular incandescent, which may only scorch things like drapery. Most safety codes now require these bulbs to be protected by a grid or grille, or by the glass and metal housing of the fixture. Bulbs over 300 watts are usually banned from residential use.

Adapted from the Wikipedia article "Heat", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki