"Efficiency lives — the rebound effect, not so much"
Shining some light on bad analysis in The Economist
Today’s guest debunker is Evan Mills, a leading scientist at Lawrence Berkeley National Laboratory. He is a widely-published expert on energy efficiency, which remains THE core climate solution and the biggest low-carbon resource by far.
Misreading of a new Sandia National Laboratories study on efficient lighting has led The Economist into the dark. In the process, they inverted the researchers’ findings, perpetuating the myth of the “energy rebound effect,” which has been postulated in theory but never shown empirically to be significant. The assertion is that the too-cheap-to-meter energy savings from energy-efficient lighting will induce people to become ravenous light hogs, increasing their demand for lumens to such an extent that lighting energy use will grow despite factor-ten improvements in efficiency compared to today’s incandescent lighting.
Perhaps a new species of “Efficiency Deniers” will be born of all this”¦. I can hear it now: Energy-efficient technologies will fuel global warming and other scourges of the earth.
The authors of the underlying Sandia study have already pointed out one of many egregious flaws in the article: Comparing today’s mixed-source lighting energy use with that projected for three and a half decades downstream (larger population, GDP, etc.) and attributing the predicted increase to LEDs (solid-state lighting):
SIR – Your surprisingly negative article on energy efficient lighting technologies (“Not such a bright idea”, August 28th) appears to have resulted from a misunderstanding of our paper in the Journal of Physics.
Unfortunately, your writer’s reasoning erred by comparing today’s per capita mixed light consumption with the projected 2030 consumption for all-solid-state lighting (SSL), rather than comparing the projected 2030 consumption with and without SSL. Because of this “apples and oranges” comparison, you drew a number of erroneous conclusions. For instance, you stated that in 2030 a tripling of electricity prices would be required before energy consumption for lighting declined. In fact, our paper shows that, for the two 2030 scenarios (with and without solid-state lighting), a mere 12% increase in real electricity prices would result in a net decline in electricity-for-lighting consumption. This “green” result is obtained while at the same time enabling consumers in 2030 to use three times more light with SSL than without it. Your amusing but hopefully tongue-in-cheek conclusions about the “greenness” of incandescent lighting would be, if serious, off-base and in our view potentially harmful.
J. Randall Creighton
Michael E. Coltrin
Jerry A. Simmons
Sandia National Laboratories
Albuquerque, New Mexico
To be more specific, The Economist says that under an LED lighting scenario for 2030 the amount of electricity needed to generate light would more than double (at today’s energy prices) while the Sandia researchers actually say that lighting energy use would be about the same in 2030 with or without LEDs. And, with real energy price increases of about 3%/year, the researchers project a 25% absolute decline in lighting energy use from 2005 levels even with an assumed ten-fold increase in lighting service levels.
It would indeed be worrisome if the energy savings from this game-changing technology were gobbled up by a penchant for cheaper lumens. However, the significant stipulated growth in demand for lighting services is based on an extrapolation of the growth that took place three centuries ago (in the days of whale oil lamps), without regard for contrary indications in the recent and far more relevant past.
Consider the highly analogous case of compact fluorescent lamps (CFLs), which are today replacing Edison’s incandescent lights hand over fist while reducing energy use by five-fold (about the same improvement that LEDs will eventually offer over CFLs on a per-delivered-lumen basis).
CFLs have made a major dent in the overall lighting market in the U.S., replacing about one in four incandescent lamp sales in just a decade’s time. Importantly, this has been accompanied by no visible change in the overall number of light bulbs sold or illumination desired by their users. By both of these measures (sockets and lumens), the speculative rebound-effect of consumer behavior is invalidated by the facts. And other well-demonstrated strategies for improving lighting systems – e.g., dimming coupled with controls for daylight harvesting – actually reduce light levels by better tailoring light output to what is needed by users and not otherwise provided by daylight. These kinds of strategies must figure big in any serious scenario for 2030, irrespective of the underlying lighting technology mix.
Source: U.S. Department of Energy
More is not always better. For rich and poor alike, the sky (i.e., a burning sun in every living room) is not the limit for lighting demand. Illuminating engineering societies around the world have actually been reducing their lighting-level recommendations for many years running, as overzealous guidelines have been seen to create excessive glare and other problems. Even granting some pent-up demand for more lumens, LEDs can save energy because their light can be more precisely directed to end-use needs and more easily controlled.
Another problem with the underlying analysis is the lack of allowance for the fact that energy policies promoting the projected expansion of LEDs will endeavor to curb their over-use via over-lighting. The analysis is also predicated on a very aggressive projection of LED cost reductions (driving their adoption), which may well not be met. In any event, LEDs will find a home in certain markets but other lighting strategies (and perhaps even new technologies not yet discovered) will also be part of a diverse mix.
LEDs stand to have their largest, earliest effect in the developing world. A quarter of humanity still lack access to electricity and instead attempt to meet their appetite for light with kerosene and other fuels, consuming a whopping 20% of global lighting energy in the process. There is vast suppressed demand for illumination in the developing world, and the rebound effect should show up most strongly here. But even in this context LEDs are already enabling vast increases in light for underserved populations, coupled with major decreases in energy use and carbon emissions. IFC, the World Bank, and the U.S. Department of Energy are betting on this.
Bottom Line: When people save money from next-generation lighting retrofits, they will have more than enough other things to spend it on than buying a pair of sunglasses and cranking up the light. The only rebound effect we need to worry about is how public understanding of emerging technologies can rebound from misinformation.
– Evan Mills, author of Building Commissioning: The Stealth Energy Efficiency Strategy
JR: The efficiency deniers at the Heritage Foundation were quick to jump all over this misreading (here). Then again they have opposed energy efficiency for a long time and lost their grip on reality a while back, calling science ‘magic’.
Good studies on the rebound effect are hard to find, since here are so many confounding factors, but one of the best recent analyses in the heavily studied area of fuel economy standards, “Fuel Efficiency and Motor Vehicle Travel: The Declining Rebound Effect” finds only a very small effect.
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