How many light bulbs does it take to lower your electricity bill?

Of all the easy green changes we can make, switching from incandescent light bulbs to compact fluorescent lamps (CFL) is among the easiest and most economical.

The average lifespan of a CFL is eight to 12 times longer than that of an incandescent bulb, resulting in fewer bulbs to replace over time. A CFL uses up to 75 percent less energy for the same amount of light as an incandescent bulb, reducing greenhouse gas emission by 2000 times its own weight and lowering household electricity consumption by approximately 12 percent per year. Even with their somewhat higher price tag, consumers save money on both replacement bulbs and electric bills.

Energy savings is so impressive that the European Union plans to phase out incandescent bulbs by 2012, and the U.S., Canada and Australia have imposed efficiency standards that exceed incandescent bulb capabilities which have changed little in over 100 years. Yet as CFLs increasingly fill store shelves and home fixtures, a few concerns remain.


Each CFL contains from one to five milligrams of mercury, a naturally occurring element so toxic that one teaspoon could permanently poison a 20-acre lake. While the amount of mercury in a CFL is less even than that in a typical watch battery, recycling the bulbs to keep the mercury out of our environment is imperative. The Colorado Department of Health and the Environment has launched a mercury-free campaign and won the cooperation of statewide Ace Hardware stores to accept CFLs for recycling. To find an Ace Hardware location, visit Some municipalities, such as Denver, also offer residential pick-up for recycling burned-out CFLs.

Light Quality

The light produced by the least expensive, highest efficiency CFLs is frequently a cooler color than the warm tones of standard soft white incandescent bulbs. The pale hues tend to evoke images of dreaded overhead fluorescent lights in sterile office environments and department store dressing rooms. Manufacturers can add a mix of phosphors inside the CFL tube to achieve warmer tones, and many manufacturers code the colors for comparison. Energy Star standardized labeling throughout the industry to help consumers accurately compare products, thus a numeric rating below 3000K (the K stands for Kelvin), will be the warmest color CFL on the shelf. A rating of 3000-3500K is white or bright white, and above 3500K the light will have more cool or blue tones. The phosphor blend that warms the light also increases the purchase price and lowers efficiency and lifespan of the CFL, but it is still a better long-term value than an incandescent bulb.

Special Usage

Initially, CFL bulbs didn’t operate properly on a dimming switch. Even now, CFLs that weren’t designed to be dimmed will flicker or go dark at low levels. Dimming a CFL that wasn’t designed for dimming also shortens the bulb’s lifespan. Look for CFLs labeled for dimming if you want to use this feature. Similarly, standard CFLs aren’t recommended for cold conditions or outdoor use. In cold conditions, standard CFLs don’t light up or produce less light, and cold temperatures also shorten the CFL lifespan. Specially designed Cold Cathode CFLs work well under such conditions as do CFLs with cold-weather ballasts, the plastic hub at the base of the glass tube. Look for these types for outdoor use.

Published 08/24/2009 at


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