LED Light: Small, powerful, and efficient. Now that they produce white light appropriate for residential settings, LEDs grouped together in a bulb pack enough punch that this 8w LED from Nexxus can replace a 75-watt PAR30 incandescent bulb.
Energy efficiency begins at home, which can often be improved easily with the right knowledge, tools and materials. This excerpt comes from The Energy-Smart House (Taunton Press, 2011) is a collection of articles on how to reduce the amount of energy your home uses, from installing energy-efficient light bulbs to insulation and windows. The following is adapted from Part 5, “Lighting and Appliances.”
Although still a relatively small slice of the incandescent-dominated lighting market, energy-efficient compact fluorescents (CFLs) and light-emitting diodes (LEDs) have gained traction over the past few years, thanks to green-building programs and some progressive local energy codes.
Be sure and look at the Efficacy at a Glance and Sources boxes (in the Image Gallery) for even more information on energy-efficient light bulbs and where to buy them.
CFLs Come of Age
CFLs were introduced in the early 1990s, but they weren’t ready for prime time. Early CFLs produced harsh blue light, hummed, and flickered, making a poor first impression. Today’s CFLs, however, produce light at around 2,700 degrees Kelvin (the measurement of light hue), mimicking the warm, amber-hued light of incandescent bulbs. Also, the old magnetic ballasts have been replaced with quiet electronic ballasts that don’t flicker.
CFLs are dramatically more efficient than incandescent light bulbs, using between 50 percent and 80 percent less energy, and they last for about 10,000 hours, nearly 10 times longer than incandescents. They also cost dramatically more. However, replacing one 50 cents, 75-watt incandescent bulb with a $3.50, 19-watt CFL saves 563 kwh of electricity over the life of the bulb. That comes to about $75 in savings, depending on the cost of electricity where you live.
On the downside, a typical CFL contains somewhere between 4 mg and 5 mg of mercury. Critics of CFLs highlight the health and environmental hazards of mercury, and special precautions should be taken if the bulbs break in your house. Proponents argue that the mercury in a CFL is far less than the amount of mercury emissions that would be released from a coal-fired power plant if you were using an incandescent bulb. Regardless, when a CFL burns out, it must be recycled so that the mercury doesn’t end up polluting the environment. Some retailers of CFLs, including Ikea and The Home Depot, offer CFL recycling. To find other recycling locations, visit the EPA website.
LEDs Are the Future
LEDs are a Silicon Valley technology, manufactured in a clean room, just like a computer chip. Electrical current runs through the 1-square-milimeter chip, exciting the electrons and creating light. A small bulblike cover focuses the light. LEDs can’t actually produce white light; white light must be created either by combining colors or by using a phosphor coating inside the bulb.
The lighting industry is betting heavily on forging ahead with significant advances in white-light LED technology in the next few years. Many of today’s LEDs, however, already perform well when used in the appropriate location.
Manufacturers describe LEDs as cool-operating lamps. While it’s true that the lit end of an LED is cool to the touch, the semiconductors do produce heat. And just as computer chips require cooling to perform properly, LEDs need thermal management. The heat sink, usually a number of large aluminum fins located near the base of the lamp, is a critical component of an LED.
LEDs are already more efficient than incandescent bulbs, producing approximately 60 to 70 lumens per watt, and manufacturers expect efficiency to surpass that of CFLs soon. Their 50,000-hour average life span translates into 34 years when used four hours a day. There are other advantages to LEDs’ solid-state engineering as well: They are immune to vibration, and their performance improves in cold temperatures, making them ideal for outdoor applications.
Cost is currently the biggest drawback to LEDs. A screw-in LED replacement for a recessed light costs about $120, but remember that LEDs are the lighting equivalent of a computer chip: Just as Intel founder Gordon Moore predicted that chip capacity would double every two years (Moore’s Law), Haitz’s Law (named for scientist Roland Haitz) states that every decade, LED prices will fall by a factor of 10 while performance will increase by a factor of 20.
Still, a word of caution is appropriate. There are some well-engineered LED bulbs and fixtures on the market, but with so many manufacturers jumping on the band wagon, there are plenty of LEDs with harsh light and poor switching and dimming response. It’s a good idea to evaluate these products carefully before purchasing.
Match the Light to the Job
Both CFLs and LEDs are available with screw-in bases as replacement bulbs for existing fixtures, but if you are building a new home or remodeling, you might consider fixtures dedicated to one technology or the other. Dedicated fixtures can lengthen the lifespan of the bulb and maximize its strengths. Both CFLs and LEDs play a role in providing ambient, accent, task, and decorative lighting, the four layers that create a well-lit room. But CFLs and LEDs aren’t necessarily interchangeable. That’s largely because CFLs are a multidirectional light source and LEDs are a point source.
Because they are multidirectional and produce large amounts of diffuse light, CFLs work well for ambient, task, and decorative lighting. They can be used nearly everywhere that incandescent bulbs are used, particularly in table lamps and in shielded sconces, where the fabric or glass adds color to the light. In the bathroom, when they’re used behind opaque glass, CFLs do a great job of lighting your face. In kitchens, in laundry rooms, and in offices, CFLs produce bright-enough ambient light to illuminate worksurfaces.
CFLs are not appropriate everywhere, however. Locations where lights are switched on and off quickly — say an entry hall or a coat closet — are not ideal because CFLs need time to attain their full brightness and because short-cycle switching reduces the bulbs’ lifespan. Also, if you’re using a CFL bulb in an outdoor fixture, make sure that it’s labeled for outside use, which means that the ballast will work in cold temperatures.
Task and Accent Lighting Require Focused Light
LEDs produce a focused beam of light. Although their relatively small output means they can’t throw light as far as some incandescents, there are plenty of circumstances where they work well as task lights. And they’re ideal for accent lights because they don’t produce UV-light that damages paintings and fabrics. Because LEDs are small and easily produced as pucks or strip lighting, they are ideal for undercabinet illumination or as accent lights hidden in coves or inside cabinets, where small size and low heat output are important.
Glare can be a concern with bright LED fixtures, especially recessed lights. San Francisco Bay Area lighting designer Eric Johnson recommends using a diffuser with recessed cans or, at the very least, recessing the bulb as deep into the fixture as possible.
Lightolier’s Calculite is a lensed fixture that uses a diffuser to create white light. Instead of coating the LED bulbs with phosphor, the phosphor is applied to the diffuser.
Under the first approach, variations in the amount of phosphor coating on each diode affect the overall color of the light. When you have multiple downlights in a room, this can result in variations in the light from the different fixtures. It’s easier to apply an even, consistent phosphor coating to a glass diffuser, improving the consistency and the color of the light. Placing the reflector above the phosphor layer results in more light output than other methods and less glare, according to the manufacturer.
A unique feature of LEDs is that a single fixture with different types of diodes can create multiple temperatures and colors of light, opening new design possibilities for accent lighting.
One last thing: Both CFLs and LEDs can be tricky to dim. The ballasts and drivers, respectively, must be compatible with the dimmers, and the light may cut out before dimming down all the way. This information is usually indicated on the product.
This excerpt is reprinted with permission from The Energy-Smart House, published by Taunton Press, 2011.