Are energy efficient lights actually saving us money?

Office buildings and workplaces are becoming increasingly energy efficient, and business leaders have recognized the value — both financially and environmentally — of “going green.”

But what if the increased utilization of energy efficient technologies, especially the adoption of LED lamps, is having the opposite effect? That’s a question being asking by energy experts, and one that could have implications both at home and at work for how we utilize our energy efficient systems.

Artificial lighting enables the once empty hours of night to be turned into productive time. At the same time, these added hours of productivity come at an environmental, social, and economic cost to society. Energy efficient lighting technologies, such as compact fluorescents (CFL) or light emitting diodes (LED), require less energy. Yet with this added efficiency comes the potential for the “rebound effect,” the idea that as we adopt more energy-efficient products we might also be using them more, cutting in to energy savings.

Andrea Hicks, assistant professor in the University of Wisconsin–Madison Department of Civil and Environmental Engineering

Andrea Hicks, an assistant professor in the University of Wisconsin–Madison Department of Civil and Environmental Engineering, often compares the rebound effect to dieting when she explains the concept to her students. Essentially, people on diets tend to think, “Well, salads are healthy. And diet pop is less bad for me than regular pop.” And then they overindulge on those things until the positive effects are completely undone.

“When we talk only about efficiency in lighting and the reduction of energy consumption, I think that we miss part of the benefits of light,” notes Hicks. “Lighting is an enabling technology, in that as a human society it decouples us from the patterns of the sun. Without artificial lighting there would be no third shift at factories, no streetlight to encourage pedestrians in a high-crime area, and no hospitals that are open to care for patients 24 hours per day. Although there is an environmental, societal, and economic cost to the use and production of artificial light, it has also conferred major benefits on us as a society.”

According to Hicks, there are two schools of thought regarding the rebound effect, which is currently an area of great debate in energy circles.

The first is that it is fairly small, and will not be significant with respect to energy efficiency, Hicks explains. The second opinion is that there is the potential for it to be very significant.

“A study came out of the Massachusetts Institute for Technology a few years ago that looked at multiple industries over multiple time scales, and concluded that although efficiency gains may save resources — energy, money, etc. — for a short amount of time, historically consumption has outpaced those gains,” Hicks says.

“In general, our policy in the United States is to push for increased efficiency to save energy and resources, such as the phase out of incandescent bulbs,” she continues. “However, if after the adoption of new, more energy efficient technology consumption increases, at the least it will negate some of the anticipated savings, also known as partial rebound, and at the worst it will completely erode the expected savings, also known as backfire.”

LEDs and the ledger

While increased usage of energy efficient lighting options like LEDs can mitigate the cost savings associated with such devices, there are still ways for businesses and consumers to save money.

Hicks explains a household or business transitioning from incandescent light bulbs to LED lamps — in this case, a lamp is equivalent to what we typically think of as a “bulb” — will see a greater use cost savings than a business or household transitioning from CFL bulbs to LED lamps. However, the initial capital cost, or purchase price, for CFL and LED lighting options is more than that of incandescent bulbs.

Second, cost savings also depend on current light consumption — essentially how many light bulbs the business or household has, and how much they are used. “In general, the number of light bulbs per household has been increasing in the United States,” notes Hicks.

Third, it depends on the cost of electricity. Households in areas with more expensive rates will see a greater monetary savings per kilowatt-hour of energy saved.

And finally there’s the rebound effect. As the efficiency of a product or process increases, there is the potential to use more — in this case, consume more light. “More light may be consumed in a number of ways, including purchasing more lights, brighter lights, or leaving current lights on longer,” Hicks says.

“One thing that can help consumers make better choices is the recent labeling changes on light bulb packaging, which are similar to nutrition labels and list the expected energy consumption of the bulb, its lifetime, and cost to use,” continues Hicks. “Companies should also evaluate their needs carefully when selecting a new lighting technology. With respect to the rebound effect, just because a technology is more efficient does not mean that it should be utilized more than its conventional counterpart.”

Hicks notes energy-saving technologies like timers and motion detectors may be helpful in reducing waste in light consumption, such as in restrooms or hallways and offices when no one is present.

“In general, due to the significant energy savings potential of new lighting technologies, it is more beneficial to upgrade to a more efficient technology than to install curtailment devices,” Hicks cautions. “With that said, there is some potential to mitigate potential increases in consumption after the adoption of a new energy efficient lighting technology through the use of these managed strategies. A motion-activated sensor for lights will help to curb the urge to leave the more efficient lights on all the time.”



Mother Nature’s bottom line

The environmental impact of using energy efficient products more often is similar to increasing usage of any product, says Hicks — they will consume more energy. “And the consumption of energy has an environmental impact that is a function of the fuel source utilized in its production. For example, electricity generated by a coal power plant has a different environmental impact than electricity generated by a wind turbine.”

According to Hicks, energy-efficient lighting technology such as CFL and LED lighting options are more complex than conventional incandescent bulbs. With respect to CFL bulbs, they contain a small amount of mercury (about 5 milligrams per bulb) that is essential to their function. In the case of LED lamps, they contain a variety of rare earth metals.

“The question with respect to both of these lighting options is should they be part of the municipal solid waste stream? Or should some of the materials be recovered from the spent bulbs at the end of their lifetime and reused, either in new light bulbs or for other purposes? In Dane County there are a variety of retailers that offer collection locations for spent incandescent and CFL bulbs; however, the recycling options for LED lamps are fairly limited,” says Hicks.

Hicks notes the lifetime of these lighting options also varies. An incandescent bulb will last for about 1,500 hours, while a CFL lasts for about 12,000 hours, and a LED lasts for about 25,000 hours of use. This means that fewer LED lamps can be used to provide the same number of hours of light when compared to an incandescent. Also, there will be fewer bulbs to dispose of.

“Due to this, LED recycling — and particularly collection — programs are still developing. In Wisconsin, spent bulbs generated as part of household waste are not legally required to be recycled; however, consumers are still encouraged to recycle their spent bulbs.”

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