Light-emitting diode (LED) technology is rapidly improving and is becoming more common in business settings. Although LEDs are not ready for all general illumination applications, they may be a good choice for a variety of uses, including parking-lot lighting, commercial signage, desk lamps, undercabinet fixtures, refrigerated cases, and overhead recessed downlighting. Although today's high-quality LEDs are more efficient than traditional incandescent bulbs, it will likely take several years before they out-perform linear fluorescent lights and compact fluorescent lamps (CFLs).

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LEDs are compact, solid-state light sources that offer significantly longer operating lifetimes than most other sources. They are also vibration-resistant, provide directional light output, turn on instantly, perform well at cold temperatures, and are dimmable. In the past, LEDs were limited to niche applications such as traffic signals, exit signs, and other uses where monochromatic LEDs displaced highly inefficient filtered incandescent lighting. But in recent years, as the performance of white-light LEDs has improved and the costs have come down, this lighting technology has become competitive in a wider range of areas long dominated by more-traditional light sources (Table 1). LEDs are a dynamic technology, and for those choosing between LEDs and conventional sources for a given application, the boundaries are constantly changing. LEDs are currently a good option for the applications that follow.

Table 1: Choosing the right applications for LEDs

Because the light sources that LEDs might replace have differing characteristics, it is important to remember that LEDs can provide more energy savings in some applications (like exit signs) than others (like parking-lot lighting). To ensure that any LED products you choose perform to your expectations, it's a good idea to try to independently verify LED performance claims before you undertake major retrofits.

LEDs are still less efficient than high-pressure sodium (HPS) and metal halide (MH) lamps, but LED fixtures can be designed with better light distribution. Some users have found LEDs acceptable for parking lots and street lighting, even if light levels are lower. A recent utility company study in Oakland, California, found that LED luminaires saved 35 percent on energy use while providing a more even light distribution pattern, longer lifetime, and superior color rendering than HPS luminaires. LED light levels were lower than those provided by the HPS lamps, but they were deemed to be acceptable. Because LED fixtures currently have a considerably greater initial cost, the simple payback period is over a decade, although this is expected to decrease as prices come down in the future. When considering LED fixtures for this application, make sure that light distribution and light levels will be adequate for your needs.

Though often neglected, overhead exit signs—which must be on 24 hours per day—can consume significant amounts of energy if illuminated with an incandescent bulb. Because LEDs are directional and monochromatic, there is no need for filters or reflectors, which diminish the output of the already inefficient incandescent light source. When illuminated by LEDs, exit signs will consume up to 90 percent less energy and require light replacement once a decade, instead of twice a year. For more information, refer to the Purchasing Advisor on exit signs.

Replacing fluorescent or incandescent lights for task lamps or undercabinet fixtures in offices can save significant amounts of energy. The directional nature of LEDs allows task lamps to be oriented to illuminate only the working area without wasting energy through the use of a reflector or by lighting unused areas. These savings can be further enhanced by delamping unnecessary overhead lighting and using occupancy sensors, which would dim or turn off the lamps at an unoccupied desk. An integrated office lighting approach has the potential to reduce lighting costs by 75 percent (Table 2). Even a modest-size company can save thousands of dollars by using this lighting strategy, which can yield a simple payback period of just a few years in existing buildings. For more information, refer to the California Public Interest Energy Research Program’s technical brief on integrated office lighting at www.esource.com/esource/getpub/public/pdf/cec/CEC-TB-33_IntegOfficeLtgSys.pdf.

Table 2: Energy savings from integrated lighting in a 120-square-foot office space

Using efficient LED task lamps to illuminate only the work area in use will allow office managers to reduce the amount of overhead lighting. This integrated lighting approach leads to significant reductions in energy costs and a smaller overall carbon footprint.

Though LEDs are still not as efficient as CFLs and linear fluorescent lamps for most general indoor lighting applications, recessed downlighting is one exception. Because LEDs are directional in nature, these fixtures do not require reflectors, which reduce fixture efficiency. Also, unlike CFLs, LEDs are fully dimmable, which is often an important consideration in this application. Currently, the LED “bulbs” for recessed downlights are very expensive—as much as $100 each—but the long lifetime and energy savings mean that the best current LEDs are cost-competitive in the long-term (Table 3). But buyers should beware. As with some other LED technologies, downlighting is still an emerging niche and has been subject to overblown vendor claims in the past. Although some LEDs perform as well as CFLs, others have proven to be only about as efficient as an incandescent bulb. To address this problem, the Energy Star program will begin certifying products that meet minimum efficiency standards beginning in late 2008 (see “How to Make the Best Choice” below).

Table 3: Sample costs of recessed downlighting

Because it uses slightly less energy and lasts four times longer than a CFL, the LED downlight is becoming competitive in terms of its long-term costs despite the higher initial price. But because many recessed downlighting fixtures are tied to a dimmer, they use an incandescent light source, not a CFL. When compared to an incandescent light source, LEDs, which are fully dimmable, are substantially cheaper to operate in the long term. But beware: Not all LEDs perform as well as the one in this table. Consumers should look for the Energy Star label beginning in late 2008 to make sure their LED downlight is an efficient model.

Retail accent lighting is a growing area for LEDs because they can vary in color, create sparkle, and aim the light precisely on an object or area. LEDs have been used in high-end retail stores for their “high-tech” aesthetic, interesting effects, and design flexibility; in cosmetics shops because they do not radiate heat; and in jewelry cases because of the sparkling appearance a point source of light lends and because their small size enables them to be used unobtrusively. Although retail display illumination with LEDs has been slow to catch on in North America, some of Europe’s largest retailers employ LEDs to create unique, attractive displays.

Businesses can effectively use LEDs in a number of outdoor applications. Using LEDs for marquee lighting and exterior commercial signage can result in better visibility, lower maintenance costs, and considerable energy savings. Many businesses have also begun to use LEDs for architectural lighting applications. Traditional architectural lighting may include neon border lights running around the top of a building or colored floodlights used to illuminate building exteriors, facades, or signs. Many high-profile businesses, such as the Hard Rock Casino and Hotel in Las Vegas, now use LEDs to provide this sort of exterior nighttime lighting. Even a traditional neon “open” sign can be replaced with a comparable LED unit for very little additional cost, while saving 75 percent or more on energy expenses. And because an LED sign will last two to five times longer than a comparable neon sign, it can be a decade or more before replacement becomes necessary.

Conventional refrigerated display cases are illuminated by fluorescent lights. LEDs offer several advantages in this type of setting, the most important being that they perform very well in cold temperatures. This is in contrast to fluorescent lamps, for which output drops appreciably. Also, fluorescent lighting dissipates waste heat inside the case, whereas the heat generated by an LED system can easily be transferred outside the case entirely, resulting in reduced refrigeration energy needs. And because LEDs are directional in nature, less light is wasted, which means even greater energy savings. As a solid-state technology, LEDs are easy to dim as well. In November 2006, Wal-Mart became the first major retailer to announce plans to use LED lighting in refrigerated display cases. In 500 stores, the company is installing low-wattage LEDs connected to occupancy sensors, which will automatically dim the lights when no shoppers are nearby. Wal-Mart believes light use will drop from 24 hours per day to 15 hours per day. Overall, the company expects a 66 percent reduction in lighting costs for refrigerated cases. Because LED technology will allow Wal-Mart to transmit waste heat outside the case, the company expects to save additional energy and money from reduced refrigeration demands. LEDs have been used in other cold-temperature applications as well, including walk-in coolers.

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Because they are a new and rapidly developing technology, LEDs are the subject of a lot of publicity and exaggerated claims. It is important to make sure that a particular LED product can meet your needs by independently verifying manufacturer claims or initiating pilot programs. The U.S. Department of Energy (DOE) has an ever-expanding set of measured performance data for commercial LED products on its solid-state lighting site (http://www1.eere.energy.gov/buildings/ssl/).

Because some LED products have not always met vendor claims in the past, the Energy Star program is scheduled to begin validating vendors’ LED performance claims for efficiency, light quality, lifetime, and beam pattern in September 2008 (Table 4). Initially, the Energy Star ratings will cover LEDs marketed for the following niche applications:

Table 4: Minimum requirements for Energy Star certification of LEDs

As light-emitting diode (LED) technology evolves, Energy Star expects the scope of these standards to change.

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LEDs are poised to move beyond niche commercial applications into more general lighting purposes. In the near term, LEDs will continue to expand into such areas as recessed downlighting, refrigerated cases, shelf-mounted undercabinet lighting, portable desk or task lamps, commercial signs, and architectural illumination. Even though LED technology is rapidly improving, it will likely be a number of years before the technology is cheap and efficient enough to displace fluorescent and high-intensity discharge (HID) light sources for general indoor illumination.

As the LED market continues to mature, the Energy Star program plans on continuing to set higher benchmarks and widen the range of products evaluated in the future. With a uniform industry standard, consumers should expect to see less of the widely varying—and often dubious—vendor claims that have plagued the industry in the past. Details on this program can be found on the Energy Star portal on the DOE web site (http://www1.eere.energy.gov/buildings/ssl/energy_star.html).

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