Getting More Efficient, But Using More Energy
How the Rebound Effect undermines energy conservation
Back in the 1970s, energy activists promoted conservation. The attractiveness of conservation waned, however, as Americans began to associate the word with sacrifice. Public relations experts responded by promoting something sexier than conservation: energy efficiency.
Everybody loves energy efficiency. A Web page formerly maintained by the Rocky Mountain Institute explained energy efficiency this way: “Savings of this sort don’t mean freezing in the dark, doing less, doing worse, or doing without. Energy efficiency is not conservation by curtailment. It means doing more with less, enjoying more comfort, providing the same or better services, but doing it a little smarter.”
There’s only one problem with the Rocky Mountain Institute’s enticing vision: efficiency improvements aren’t working. While homes and appliances are increasingly efficient, our homes use more electricity every year.
A group of authors — Jeffrey Harris, Rick Diamond, Maithili Iyer, Christopher Payne, and Carl Blumstein — discuss this paradox in a paper, “Don’t Supersize Me!” The authors write, “Despite notable gains in the energy efficiency of building envelopes, lighting, HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building., and plug loads, total primary energy use has increased over 30% in US residential buildings since 1978, and more than 65% in commercial buildings. The growth in buildings sector energy has been significantly faster than for all US energy (25%).”
Efficiency improvements lower the cost of energy required to perform a unit of work — and that’s a problem, since lower energy costs allow consumers to spend more money for larger houses, more refrigerators, more televisions, and more frequent (and longer) showers. The result: efficiency improvements often result in higher levels of energy use.
Reviving a focus on conservation
A large energy-efficient house often uses much more energy than a small house that isn’t energy-efficient. Now that we are establishing new national goals to reduce greenhouse gas emissions, it’s time to return to our roots and encourage energy conservation.
One of the “Supersize” paper’s authors, Christopher Payne, is an energy analyst for the Lawrence Berkeley National Laboratory. Payne posed the following rhetorical question: “If you accept the idea that there are limits to total consumption — because of limits to the total amount of CO2 we can produce — what does that mean in terms of our energy policies?”
According to the “Supersize” authors, “In many cases policy-makers seem confused (or deliberately vague) about efficiency versus conservation, perhaps in the hope that efficiency improvements will be powerful enough to reduce absolute energy use and carbon without any constraint on consumers or consumption.”
Efficiency programs are sometimes counterproductive
The “Supersize” authors point out that some characteristics of energy-efficiency programs undermine the principle of conservation. They write, “A study by Prahl (2000) suggests that the Home Energy Rating System (HERSIndex or scoring system for energy efficiency established by the Residential Energy Services Network (RESNET) that compares a given home to a Home Energy Rating System (HERS) Reference Home based on the 2006 International Energy Conservation Code. A home matching the reference home has a HERS Index of 100. The lower a home’s HERS Index, the more energy efficient it is. A typical existing home has a HERS Index of 130; a net zero energy home has a HERS Index of 0. Older versions of the HERS index were based on a scale that was largely just the opposite in structure--a HERS rating of 100 represented a net zero energy home, while the reference home had a score of 80. There are issues that complicate converting old to new or new to old scores, but the basic formula is: New HERS index = (100 - Old HERS score) * 5.) used by Energy Star HomesA U.S. Environmental Protection Agency (EPA) program to promote the construction of new homes that are at least 15% more energy-efficient than homes that minimally comply with the 2004 International Residential Code. Energy Star Home requirements vary by climate. and a number of utility-sponsored programs requires smaller houses to have higher levels of energy efficiency, component by component, in order to achieve the same HERS score as a larger house. Holding constant domestic water heating efficiency, the study found that in Pittsburgh, Pennsylvania, a typical 1,537-square-foot home would need to install a furnace rated at 96% Annual Fuel Use Efficiency (AFUEAnnual Fuel Utilization Efficiency. Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. ) to achieve a HERS score of 86” — the authors are referring here to the old HERS scoring system, not the new HERS index — “whereas a 5,564-square-foot house would require only an 80% AFUE furnace. Building a bigger house efficiently will typically ‘save’ more energy than building a smaller house at the same efficiency level, but the larger house will still consume more energy.”
In a letter to the editor of Home Energy magazine (July/August 2009), Li Ling Young makes the same point. “The HERS index is plagued with this simple and damning flaw: Scoring is partially based on the size of the building. Larger homes that use more energy can score as well as or better than smaller homes that use less energy.”
The Rebound Effect
One energy expert — Andrew Rudin, a consultant from Melrose Park, Pennsylvania — has concluded that efforts to improve energy efficiency often backfire. In a 2004 paper, “How Greater Efficiency Increases Resource Use,” Rudin argued, “Increasing the efficiency of a process usually lowers costs and increases consumption.” The mechanism documented by Rudin — whereby energy efficiency improvements lead to increased energy use — is called the “rebound” or “snapback” effect. (For an in-depth discussion of the rebound effect, see The Jevons Paradox.)
Reviewing the historical record, Rudin unearthed countless predictions that efficiency improvements would lead to lower consumption. Yet “in each example — gasoline, paper, and electric consumption — U.S. per capita consumption increased as consumption became more efficient.”
As we face a climate-change crisis, many Americans are questioning fundamental assumptions about economic development. “One of the problems of the efforts over the last 25 years to promote energy efficiency is that we haven’t necessarily given people everything they want,” said Payne. “Some of the growth of the green building movement reflects that. Too often we tend to frame the debate in terms of giving something up, as if we are required to be less comfortable — ‘If I live in a tiny home that will make me less happy instead of in an enormous home which makes me more happy.’ Some people are now saying, ‘Wait a minute — this was supposed to make me feel happier, but I don’t feel happier.’ ”
Rehabilitating the idea of sacrifice
It wouldn’t necessarily be a bad thing if our current environmental crisis requires us to give something up or make sacrifices. “Energy conservation does not always involve sacrifice, as President Carter’s sweater implied, but in some cases it may — just as other important personal and collective goals sometimes call for sacrifice: sending kids to college, caring for an aging parent, reducing roadside litter, or countering terrorism,” the “Supersize” authors wrote. “The question is how much sacrifice is necessary, and how much we are willing to accept. Slower growth in energy consumption can mean real sacrifice for many in the developing world who still await access to electricity or clean water, but for most of us fortunate enough to live in the U.S. it may mean a modest shift in our aspirations, deciding to be satisfied with sufficiency rather than pursuing excess.”
Last week’s blog: “Tackling the Plug Load Problem.”
- U.S. Department of Energy
Jun 29, 2009 9:27 PM ET
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