LIGHTING LEXICON

Those of us who grew up using incandescent bulbs are used to associating the term “watts” with brightness. A 25 watt incandescent bulb, for example, provides much less light than a 100 watt bulb. Watt, however, is actually a unit of power: It refers to the amount of electricity the bulb consumes per second.

But that leads to difficulty when comparing incandescent bulbs to their modern counterparts. A compact fluorescent light (CFL) bulb that produces the same amount of light as an old 100 watt incandescent might draw only 23 watts, and a comparable light-emitting diode (LED) bulb might draw only 15.

A more accurate way to compare different lighting technologies is by lumens— a measure of brightness. A higher number of lumens means a brighter light. CFL and LED bulbs today are packaged with a “lighting facts” label that outlines its lumen output, along with facts such as its expected life and the watts used. In general, to get the same amount of light as an old 100 watt bulb, you want to select a replacement that offers about 1,600 lumens. A 75 watt incandescent provides about 1,100 lumens, and a 60 watt version provides about 800 lumens.

Another term used to differentiate CFL and LED bulbs is Kelvin (K), which refers to color temperature. Warmer, yellower lights have lower Kelvin temperatures, of 2,700 to 3,000, while cool, bluish white lights fall into the range of 3,600 to 5,500 K. Cooler lights are preferred for work areas that require visual acuity because they provide more contrast, while warmer lights are more often used in living spaces.