Since the federal government mandated in 2007 that light bulbs needed to be 25 percent more energy efficient than incandescents, the industry has solved the problem by creating consumer-friendly light-emitting diode, or LED, bulbs. It used to be that all you needed to know was whether your lamp took 60, 75 , or 100 watts. Homeowners now are faced with learning a whole new lingo.
There are some unfamiliar terms as they relate to LED lights — “lumens,” “CCT,” and “CRI.” First, what are lumens and how does the term relate to watts? OK, in concept, a “lumen” is a measure of the output of light, whereas a “watt” is the amount of energy needed to send out this light. It turns out that a 60-watt incandescent bulb produced around 800 lumens of light, and a 100-watt bulb emitted around 1,600 lumens . The main advantage of an LED is that it takes a lot fewer watts to produce 800 or 1,600 lumens. An 800-lumen LED bulb needs only 13 watts of energy. Other advantages to LED lights are that they release much less heat than incandescent or halogen bulbs and last much longer. An Energy Star-qualified LED bulb will last as much as 25 times longer than a comparable traditional incandescent, according to the US Department of Energy.
The most common complaint against LEDs, and I share this one, is that the light emitted is too white. Correlated color temperature, or CCT, is a measure of how white the light is. What does this have to do with a light bulb? It relates to the perceived “color” of the light. The “temperature,” based on the Kelvin scale, is a way to indicate how warm or white a light is. If you like the color of the old incandescent or halogen light bulbs, then look for LEDs that are less than 3,000 Kelvin. In some situations, a bright-white light may be what you want. Natural bright daylight is rated 10,000 Kelvin. At even 4,500 Kelvin, the light emitted is very white, so be sure to check it out first, if possible. Some stores have lighting labs that demonstrate different bulbs and their effects. I highly recommend that consumers see a light in person before investing in cases of them. Just remember this: The lower the number, the warmer the color.
The color rendering index, or CRI, refers to how closely the light bulb makes something look like its actual color as seen in natural daylight or with an incandescent light bulb. This does not have to do with the color of the light, but how it renders the colors of an object. So if that is important to you, the closer the CRI is to 100, the more it approaches the actual colors.
One more thing to consider — dimmers. Not all LED bulbs are compatible with dimmers. If you are remodeling and putting in all new fixtures, this is the time to put in compatible dimmers.
If you are building, you can install fixtures designed just for LED bulbs, or “integrated” LED fixtures. These may be quite a bit more expensive than simply using LED bulbs in the traditional recessed light fixtures, but they could give you the ability to create a more nuanced lighting scheme, possibly even different colors controlled by your smartphone.
Chris Chu is an architect in West Newton who specializes in residential design. Send questions to Address@globe.com.