Elasticity contradictions

A: Increasing the efficiency of an energy consumptive activity will lower the cost of the services derived from that activity – that is, it will change the price of the “energy services” derived from the fuels, such as lighting, transportation goods or services, heating or cooling, industrial processes, etc.Economic actors respond to price changes in two general ways:

1. Increasing the utilization of that energy service to increase outputs or incomes. For example, a low-income resident may now heat his or her home more often or heat more areas of the home after weatherizing their home, because it is now far more affordable to heat. (In economics speak, this involves ‘elasticities of demand,’ or the responsiveness of demand to changes in the price of goods and services)
2. Re-arranging the factors of production or goods and services consumed to substitute now-cheaper energy services for other goods or services (maintaining the same level of output or income). For example, a more efficient heat plant may enable a chemicals plant or metals smelter to raise temperatures in industrial processes to extract high quality product from poorer quality inputs (substituting energy for materials) or to reduce process times (substituting energy for labor). (In economic terms, this involves ‘substitution elasticities,’ or the ability of firms or consumers to take advantage of lower prices to productively re-arrange the production inputs or consumer goods they utilize).

Both of these dynamics are “rebound effects,” a term for any economic mechanism that leads to a rebound, or increase, in demand for energy following an improvement in energy efficiency that lowers the effective cost of that energy service.There are other rebound effects as well (for a quick description of each, see the summary here). Our report, “Energy Emergence” surveys more than half a dozen distinct rebound mechanisms, some of which are fairly direct (like the two above), others that are more indirect (like the impact of money saved through efficiency measures as it is re-spent in the economy on other goods or services that in turn require energy to produce). Still more effects are only visible in the aggregate, at the macro-economic scale, as economies respond in a variety of ways to widespread improvements in energy efficiency.

A: No, not always. Although in some cases, it is possible that efficiency improvements will “backfire,” driving a rebound in energy that fully compensate for the initial energy savings, increasing energy demand overall. While backfire is by no means the norm, it is possible in some cases (we’ll explore conditions that are likely to lead to backfire in a later question).As “Energy Emergence” concludes, “Rebound effects are real and significant, and combine to drive total economy-wide rebound in energy demand with the potential to erode much (and in some cases all) of the reductions in energy consumption expected to arise from below-cost efficiency improvements.”

Think of it this way: rebound effects mean that for every two steps forward we take in energy savings through efficiency, rebound effects take us one (and sometimes more) steps backwards. We may still move forward, but not as much as we initially expected.

A: Rebound matters because the magnitude of rebound effects determines how effective below-cost efficiency improvements are at contributing to lasting reductions in total energy use and therefore greenhouse gas emissions.Energy efficiency has frequently been cited as the single greatest contributor to emissions reduction and climate mitigation strategies, by everyone from the International Energy Agency and Intergovernmental Panel on Climate Change to consultants like Amory Lovins’ Rocky Mountain Institute and McKinsey to efficiency advocates and environmental NGOs. The IEA counts on efficiency for roughly half of the emissions reductions needed in their “Blue Map” climate stabilization scenario (graphic below), for example, while President Obama told reporters in 2009 that with efficiency, “we can save as much as 30 percent of our current energy usage.”

So we’re counting on energy efficiency to do quite a bit of “climate mitigation work,” so to speak.

The problem is that all of these estimates are based on an assumption: that energy efficiency reduces energy demand in a linear, direct, and one-for-one manner. An X% gain in efficiency leads to an equivalent X% reduction in total energy use.

But the economy is anything but direct, linear, and simple, especially when responding to changes in the relative price of goods and services. When a good or service or input to production gets cheaper, consumers and firms use more of it, find new cost-effective uses for it, re-invest any savings in other productive activities, and the economy overall gets more productive overall, driving economic growth and activity.

That’s the rebound effect, and it means that we can’t assume that improving energy efficiency by 20%, for example, will reduce energy demand by 20%.

If we don’t accurately and rigorously account for rebound effects, we risk over-relying on energy efficiency to deliver lasting reductions in energy use and greenhouse gas emissions, and we will fall dangerously short of climate mitigation goals.

A: Rebound effects differ in scale, depending on the type of energy efficiency improvements we’re talking about, and where in the economy we look. In very few cases are rebound effects “very small” or insignificant.Dozens of academic studies have examined the empirical evidence, conducted modeling inquiries, and otherwise tested the scale of rebound effects. While there is much more work to be done to determine the precise scale and impact of rebound effects in different circumstances, the conclusion is that rebound effects are significant and cannot be ignored in energy and climate analysis and policymaking. See the following three questions for summaries of the scale of rebound in different circumstances…

A: In rich, developed nations, if we improve the efficiency of end-use consumer energy services, like cars, home heating and cooling, or appliances, the literature indicates that direct rebound effects alone are typically on the scale of 10-30% of the initial energy savings. Additional indirect and macroeconomic effects may mean total rebound erodes roughly one quarter to one third of expected energy savings in these situations.Rebound here is smallest in cases when demand for the energy service in question is already saturated (that is, we use as much of it as we would care to use), and highest in cases where the cost of the energy service is a key constraint on fulfilling demand for that service. For example, if a wealthy homeowner already reliably heats all the rooms in his or her house to 70 degrees, he/she wouldn’t increase the thermostat to 77 degrees just because our heating system got 10% more efficient. But if a poorer household can’t afford to turn the thermostat up, or only heats one room of the house with a small space heater, because the house is too drafty, then if the house gets weatherized and more efficient, that household is likely to use more energy to heat their home. In general, end-use consumer efficiency improvements in rich, developed economies will still lead to a net savings in energy, although rebound effects shouldn’t be ignored even here.

A: No, rebound effects are almost certainly larger in poorer, developing nations.