Because we typically associate “temperature” with heat production, color temperature (CT) can be confusing. On the CT scale, which expresses electromagnetic radiation in degrees Kelvin (K), higher values apply to “cool” bluish white light, while lower values apply to the “warm” yellowish light of incandescents. A related measure called the color rendering index (CRI) assesses how faithfully a lamp reproduces colors compared with natural light. Look for a CRI of at least 75, which is the Energy Star minimum. But many LEDs are available in CRI 85 or higher, which will generally provide very good-quality lighting.

How many contractors does it take to screw in an LED bulb? Well, just one, but only after a bit of head scratching. While new technology has made every aspect of our lives richer and more efficient, it has complicated simple things like choosing and changing a light bulb. Shopping for LED bulbs is like shopping for a smart phone — it can make you feel stupid, because there are so many choices and a lot of what you thought you knew about light bulbs doesn't apply to LEDs. In what follows, we'll look at the key concepts you need...