Lighting accounts for one-eighth of total U.S. electrical consumption and 15% of the electricity consumed by the residential and commercial sectors of the economy. There are enormous opportunities for efficiency gains in those sectors by widespread adoption of the technology most Americans first encountered as the glowing lights on appliances: the light-emitting diode (LED).
LEDs are “solid-state” devices made of materials similar to those in computer chips. They produce illumination by allowing electrons to flow across an electrical junction (diode) and drop into a lower energy state, releasing the energy difference as light. LEDs generate relatively little heat, last 100 times longer than incandescent light bulbs, and convert more of their electrical energy to light. Unlike compact fluorescent lamps (CFLs), they do not require bulky sockets or fixtures, contain no hazardous substances (such as the mercury in CFLs) or breakable components, and can be embedded directly into ceilings or walls.
LEDs generate relatively little heat, last 100 times longer than incandescent light bulbs, and convert more of their electrical energy to light.
LEDs are the most efficient technology for conventional forms of lighting, such as home and office illumination, as well as streetlights. The amount of light emitted by a lamp, weighted by the sensitivity of the human visual system, is measured in units called lumens. A typical incandescent lamp (traditional light bulb) that consumes 60 watts of power produces around 800 lumens. A compact fluorescent lamp emits the same amount of light while using only 13 watts. And an LED lamp consumes only 10 watts to give off the same 800 lumens.
The U.S. Energy Information Administration (EIA) projects that by 2020, LEDs will produce more than 150 lumens per watt. Their efficiency, however, declines over time.
The rising market share of CFLs was chiefly responsible for the fact that overall lighting efficiency in the United States increased from 45 lumens per watt (lm/W) in 2001 to 58 lm/W in 2010. Analysts expect further efficiency gains—and significant energy cost savings—as the use of LED technology increases. A 2013 report from the U.S. Department of Energy found that if nine major residential and commercial lighting applications switched to LED sources “overnight,” the immediate annual savings would be about $37 billion.
The relatively high cost of LED fixtures has slowed their acceptance nationwide, despite the potential savings in operating cost over time. But LED market share is expected to expand with improved technology and manufacturing techniques, lower retail prices, and growing awareness that the longer expected lifetimes of LED lights can offset their higher initial cost compared to CFLs. One study estimates that by 2030, LED lighting will grow to 74% of lumen-hour sales in the United States. That is one reason that the EIA projects that residential energy use for lighting will decline more than 50%—in the range of 1,000 kilowatt hours per household per year—from 2012 to 2040.
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