The very week of the announcement that the researchers who helped create energy –efficient LED lighting received the Nobel Prize, two nay-sayers on efficiency find a forum in the New York Times to express their poorly-reasoned doubts .
Michael Shellenberger and Ted Nordhaus, who have been trying for years to challenge the seemingly clear idea that saving energy actually ends up saving energy, argue that “it would be a mistake to assume that LEDs will significantly reduce overall energy consumption.” This despite these authors’ noting that the president of the [Swedish] Institute of Physics said in describing why these inventors won the Nobel: “With 20 percent of the world’s electricity used for lighting, it’s been calculated that optimal use of LED lighting could reduce this to 4 percent.”
Instead, Shellenberger and Nordhaus declare, the Royal Swedish Academy of Sciences was wrong: more efficient lighting will simply lead to more use of lighting, they claim, negating any savings.
This isn’t the first time they’ve touted this “rebound” notion as if it were scientifically sound.
What’s wrong with the rebound concept?
A few years ago, we at NRDC examined what rebound enthusiasts were saying, but did so from a rigorous scientific viewpoint. As our May 2011 article in Electricity Policy noted, we found that most rebound enthusiasts don’t even have a scientific hypothesis, much less any supporting evidence. I will show you an example of this problem below.
Better, we found that good energy efficiency policy sometimes delivers the opposite of rebound, i.e., a little energy efficiency leads to more and more and more reductions in usage and pollution. For example, on an economy-wide basis, the actual reduction in energy use for a region like the state of California that has been implementing energy efficiency policy for decades is far larger than a simple projection of savings--such as the one that Shellenberger and Nordhaus criticize the Royal Swedish Academy for making--would suggest.
What are Shellenberger and Nordhaus—well-known advocates for nuclear energy--trying to say in this article—what is their hypothesis? They conclude that “LED and other ultraefficient lighting technologies are unlikely to reduce global energy consumption or reduce carbon emissions”, so apparently their hypothesis is that LEDs won’t reduce energy consumption at all! Or maybe it isn’t—their article is not clear on the point. This is a major problem in itself—the absence of a clear exposition of what they are trying to prove demonstrates how fuzzy their thought process is. And incidentally, also makes it more difficult to refute, which may be a good debating tactic but is bad science.
How could lighting energy use rebound, in principle?
The hypothesis that LEDS won’t save energy at all goes far beyond even the supposedly factual assertions they make in their article, where they say that “The I.E.A. and I.P.C.C. estimate that the rebound could be over 50 percent globally.” How does a piece of evidence that rebound could be over 50% (but by implication could equally be a lot smaller, which is what a full reading of the reports shows) suddenly turn into an assertion that rebound is likely to be 100%?
What are possible mechanisms of rebound? People could use more lighting, or the same amount of lighting for more hours, or could use less efficient fixtures and designs.
Why lighting rebound doesn’t happen in practice
Careful examination of these factors shows that policies and consumer preferences are steadily pushing in the opposite direction—saving more energy not less.
In the developed world, and also in rapidly developing countries like China and India, the amount of lighting is influenced by consumer preferences and by lighting standards of practice and efficiency codes. These standards and codes allowed or even demanded ever more lighting until about the 1970s. At that time, the need to save energy caused a re-examination of how much light we need and a steady lowering of illuminance recommendations. The amount of light being provided is now going down, as the efficiency of providing it is going up. Both are a consequence of decisions that we want to reduce energy waste in lighting.
As countries develop, more spaces are illuminated than when they were poorer, but this was true even when the lighting was inefficient. Glitzy outdoor lighting, even with inefficient sources, is still so cheap that it is used whenever the consumer wants it. But with more attention being paid to energy savings, this trend has been of limited and declining significance.
The number of hours that lights are on is also going down as a result of policies designed to save energy. In 1970, it was common for the whole lighting system of a high rise building in America to be turned on and off from a central circuit box and for all the lights to be on 24/7. Now energy codes and common practice allow workers to turn off their lights and provide automatic controls to do it for them if they forget.
And new fixture designs allow the use of more indirect lighting that users are comfortable with at lower levels of illumination and of energy use.
In sum, the goal of saving energy is resulting in less illumination, not more, and in lighting systems that are easier to turn off and dim, and in better lighting designs that make better use of the same amount of light. Improving the efficiency of the light source by substituting LEDs will complement these outcomes, not undermine them.
No significant rebounds in the developing world, either
What about in the developing world? For the more prosperous regions, lighting, which is just not all that expensive, will resemble the developed world. Perhaps levels of illumination will be a little lower and more attention will be paid to turning the lights off when not needed, but the difference will not be huge. This is what I found when I worked in Beijing with Chinese lighting experts to write their energy code for lighting, and it is what my colleagues found when the worked on the Energy Conservation Building Code in India.
So the same argument applies: LEDs will accelerate a trend to more energy savings.
The only place where rebounds are likely is for very poor communities where lighting is now provided by kerosene lamps that send harmful particulates into the air. In this case, one has to note that LEDs are over a thousand times more efficient than kerosene. So even when we replace a kerosene lamp with an LED lantern that provides 100 times a much light, we are saving 90% of carbon pollution. And that’s assuming the LED is powered by fossil fuel—most likely these poorer communities lack electric service so the very-low-energy LED will be powered by rechargeable batteries charged by solar cells.
Is there evidence for significant rebound in light source efficiency?
LEDs are not the first example of a new source that cuts lighting energy use by over two-thirds. Compact fluorescent lamps were introduced in significant numbers in the 1990s and have been the subject of incentives and promotions by utilities and other entities many times in the interim. They now provide about a quarter of the lighting in American homes.
Since most utility programs must be evaluated by outside parties, we have solid evidence from all over the U.S. on potential rebounds. What has been found is that rebound effects are very small where they exist at all.
It would be a shame if poorly-reasoned ‘rebound’ claims convinced consumers and policy-makers that energy efficiency is pointless and not worth pursuing to reduce climate pollution. Based on decades of experience delivering great consumer and environmental benefits through energy efficiency, nothing could be further from reality.