Understand These Numbers on Light Bulb Packaging When Buying LEDs

Today, light-bulb manufacturers are required to include a great deal of information on their packaging. Some of these figures, like the bulb's average energy costs per year, are pretty self explanatory, but others, such as the color-rendering index (CRI) are less clear. Understanding all of these figures (and LED Terminology) is key in determining which light bulbs will provide the best value for your home.

One of the first things consumers might look at is the average life expectancy of the bulb. With your standard incandescent bulb, this is usually something like 1,000 hours, or just under a year if the bulb is used for an average of 3 hours per day. With a high-end LED bulb, you might see a figure like 25,000 hours or even 50,000 hours. I'll save you from doing the math -- that's as much as 45 years of hypothetical usage. Throughout that entire time, you'll be paying significantly less on energy than you would have been with your old light, so an LED bulb that's built to last can make for a terrific investment.

As for that CRI number, think of it like an average grade for the bulb's ability to faithfully reproduce various colors in comparison with natural daylight. During testing, a bulb gets a grade of 1 to 100 for each color. For instance, a bulb that scores high with greens will make limes look just as green as they would in the sunlight. These color grades get averaged, and the result is the CRI number -- the higher the better. Bulbs with CRI numbers in the 80s are typically very good, high-end lights, although we're seeing some consumer-level bulbs, like the recently announced Cree TW Series LED Bulb, start to creep up into the 90s. If you're looking for clear, vivid colors from your light, seek out bulbs such as these.

For brightness, you'll want to look for the number of lumens that the bulb puts out. A lumen is a unit of measure for light output. In essence, a bulb is simply a device that converts watts (electricity) into lumens (light), and generally speaking, the more lumens a bulb produces, the brighter it will appear. Remember that not all bulbs are created equal -- some are dramatically better at converting watts into lumens than others. An 8-watt bulb might produce more lumens than a 10-watt bulb, for instance. If brightness is your chief concern, check the boxes carefully.

Don't get confused by color temperature, either. Color temperature, measured on the Kelvin scale, is not an indication of how hot or bright the bulb gets. Instead, it's a measure of the color of the light that the bulb produces. Think of a flame -- it's orange and yellow at first, but a really hot flame glows blue. Color temperature works the same way. Lights on the low end of the spectrum (2,700 to 3,000K) will have a warm, orange color, whereas lights on the high end (4,500 to 6,500K) will look more bluish. Lights that fall somewhere in the middle of the scale should shine bright white.


No matter how you end up lighting your home, the important thing to remember is that you'll still have the power to decide what's best for you. No one is forcing you to use a certain kind of light bulb -- the government is just forcing manufacturers to build you better ones. After 134 years of incandescents, maybe it's about time.

From: cnet