Rebound

Is efficiency a magic weapon for environmental protection? More efficient technologies can also lead to more rather than to less consumption. The rebound effect has entered public debate. In particular, increases in energy efficiency are being criticised. However, in order to be able to assess rebound effects, clear distinctions have to be made.

By Reinhard Madlener

Translated from the German by Kerstin Haep

In recent years, the issue of rebound effects has become increasingly significant in scientific and political debates in Germany as well as internationally. This is a crucial step because the government regards increases in energy efficiency as a proven and cost-effective means to reduce the use of fossil fuels and therefore also the amount of greenhouse gas emissions. Hence, it is important to understand the opposing trends of these expected savings as well as the influence of this methodology and of the system boundaries (and also of possible distortions of the estimates) on the size of the rebound effect. Regarding energy policy, this means that the policies are neither as effective nor as cost-effective anymore as they would be if the rebound effect amounted to zero.

Despite a more than 30-year-old debate over different concepts in the scientific literature, the definitions and uses of the term 'rebound' still vary widely. Nevertheless, measuring rebound effects allows us to evaluate how expected or rather professionally-calculated energy savings are impeded (rebound effect between 0 and 100%), eliminated (rebound of 100%) or even overcompensated (rebound of more than 100%, also called 'backfire') due to behavioural responses to more cost-effective energy services that result from technical efficiency improvements. For example, people who drive vehicles that are more energy efficient have a higher mileage (this was empirically verified for Toyota Prius drivers and is a fact that should not be neglected). Another example is the additional consumption of heating energy following energy- efficient building renovations (for example, because of unmet personal needs or against one's better judgement – that is, for example, when people keep heating and ventilating the way they used to despite more efficient insulation and new heating technologies).

The term rebound must be differentiated from the energy performance gap (EPG), a term referring to the difference between the calculated energy requirements and the amount of energy actually used, for example, following the energy-related renovation of a building. This difference is always indicated as a percentage. Another important measure in the context of energy policy is the energy savings deficit (ESD), which refers to shortfalls in expected energy savings after an energy-related renovation process. The ESD is indicated in per cent as well. Such measures help to distinguish between behavioural effects (the question here is whether there is a difference between the conscious behaviour of a person prior to and after the increase in efficiency) and technical effects (which may also be related to deficient technology or imprecise technical calculations). 

Prebound – a term coined by Ray Galvin (Sunikka-Blank and Galvin 2012) – refers to the phenomenon of having used less energy (even prior to the increase in energy efficiency) than had been calculated and expected. Rebound effects are often typical for energy-efficient buildings, while it is rather 'prebound' effects that tend to be seen in poorly insulated buildings. This leads to at least two conclusion. First, energy and CO2 savings that can be realised through energy-related renovations are quite difficult to predict on the basis of previously calculated savings. Second, non-technical energy savings that can be realised through changes in behaviour have the potential to clearly surpass energy savings achieved by means of technical improvement, which has significant relevance for optimal policy development.

Rebound effects include direct effects (increased demand for energy services that have become cheaper due to increased energy efficiency – a price effect), indirect effects (increased demand for other energy and resource consuming products and services, because one energy service has become cheaper as energy costs are saved due to increased energy efficiency – an income effect) and macroeconomic effects (increased energy efficiency has the potential to change supply and demand in the economy as a whole, and leads to structural changes, and also usually to growth which encourages the consumption of resources).

If the macroeconomic rebound effects are considered not only on the level of the national economy but also globally, the research methodology becomes very complex and demanding. Through increased interdependence of national economies as a consequence of advancing globalisation, global rebound effect is, in any case, a factor that should not be underestimated. An energy efficiency policy in one country could provoke rebound effects in other countries, which ultimately could lead to an increase, instead of a decrease, in energy consumption. This should be thoroughly considered when exporting energy-efficient commodities.

Furthermore, energy rebound effects could lead to additional consumption of non-energy resources and could, as a result, shift the problem (note that on a micro-level, although the use of a particular energy service saves energy compared to the situation before the improvement in efficiency, an increase in material consumption may result). 

Thus, resource efficiency as a whole or rather the absolute decoupling of economic growth and non-renewable resource consumption must also be borne in mind.

Finally, the energy and resource consumption (including precious materials and rare earth elements) as well as the economic and social impact of using renewable energy technologies represent an aspect of the energy transition that is still insufficiently explored but also has rebound potential (by means of energy technologies that were not attractive enough commercially until they showed an increase in efficiency).

In this context, it is crucial to, first of all, find out, by means of energy systems analysis (Life Cycle Cost Analysis, Life Cycle Sustainable Assessment, etc.), where and how the energy transition also leads to negative effects (for example, child labour in Malaysia), and then to minimise these effects accordingly.

Despite the complexity of rebound effects, it is certain that it will be easier to find solutions to the enormous energy and resource policy challenges with a profound transformation of society towards sustainable development and an improved transparency of the consequences that result from our own actions than by merely using technological fixes and trusting blindly that technical progress is predominantly only a positive development.

Prof. Dr Reinhard Madlener directs the Institute for Future Energy Consumer Needs and Behaviour (FCN) at RWTH Aachen University. In 2011, he wrote the expert report on rebound effects for the Growth, Prosperity, and Quality of Life’ study commission established by the German Bundestag (the lower house of the German parliament).

More articles to this topic we present not only online but in our magazine Rebound. It ist finely illustrated and good readable on tablets and screens and contains all articles and pictures as well as numbers and citations.