The rebound effect

Puzzles in the billing for heating in the new, so energy-efficient apartment: The greatly announced savings were not nearly reached. On the contrary, it will be expensive again. Triple glazing, insulation, heat recovery - everything for the cat? The list of potential culprits is long: Was blundered? Wrong calculated? Or is all this hooliganism about energy efficiency just a sales mockery?

Those who actually go on a lengthy search for the cause of the failure in terms of energy efficiency end up all too often in front of the mirror and have to take their own nose: The resident himself has failed because of the so-called rebound effect. The phenomenon, discovered in the middle of the 19th century, describes the difference between the calculated energy consumption and the actual energy consumption of a building. In the deceptive assumption that the sustainable building fabric saves energy by itself, it was treated too carelessly - and finally the bill is presented.

Prebound & rebound

The terms rebound and prebound are understood to mean the impact of user behavior on energy efficiency. It has been shown that these effects the expectations or results of z. For example, they have a strong impact on sustainable buildings.
For example, a study from the University of Cambridge, based on data from some 3.400 buildings, found that residents use an average of 30 percent less than the building's calculated energy index. This phenomenon is called the prebound effect, the effect being the more pronounced the worse the energy index is. Simplified: Due to the poor energy efficiency, heating is saved. Therefore, there may be false expectations in energy efficiency measures: Since renovations can not save energy that is not consumed at all, there are consequences for the cost-effectiveness of energy-efficient renovations.
Conversely, this also applies to the rebound effect. It identifies the difference between the potential savings from energy efficiency measures and the actual savings. Paradoxically, increasing efficiency can increase overall energy consumption.

And the rebound effect has been proven many times, as well as his "nicer" brother Prebound: For example, 2012 was compared in a study, the actual energy consumption of 3.400 households in Germany with the calculated energy consumption. It turned out that the actual consumption on average is 30 percent below the calculated consumption. Particularly high differences were found in non-rehabilitated, energy-inefficient building stock and households where no efficiency measures such as equipment replacement were carried out. Here the energy consumption was always calculated and estimated higher than it was in reality.

The main reason for this discrepancy has been the human factor in building management. For example, many households consume less energy because they keep the room temperature lower than assumed in theoretical energy consumption calculations. In homes that are particularly energy inefficient, residents are often forced to behave particularly sparingly to reduce costs (the prebound effect).

It is particularly violent when both effects occur in a row: The unrefurbished apartment is heated only sparingly, well below the actual energy consumption, after a renovation energy is let out the pig. Conclusion: The difference can take on enormous proportions.

And sustainability works

The study "Evaluation of consumption characteristics of energy-efficient renovated residential buildings" by the German energy agency dena 2013, which examined the data of a total of 63 thermally renovated buildings over several years - before and after energy efficiency measures - proved that sustainable building works in spite of the phenomena. The result is impressive: with a calculated final energy consumption of 223 kWh / (m2a) on average before the refurbishment and a projected demand for 45 kWh / (m2a) on average after the refurbishment, the aim was to save 80 percent energy. After the actual refurbishment, an energy consumption index of 54 kWh / (m2a) and an average energy saving of 76 percent were reached on average. In plain English: The planned energy efficiency is actually realized. However, it is difficult to calculate the user behavior.

Rebound effects

• Direct Rebound Effect - You buy a car with a more efficient engine, but opt ​​for a larger car or use your more efficient car more than the previous one.
• Indirect Rebound Effect - Now that you're driving a more efficient car and have reduced fuel costs or CO2 emissions, treat yourself to a trip by plane rather than by train or car on your next vacation.
• Macroeconomic rebound effect - An increasing demand for efficient vehicles leads to changes in the production and demand structure. For example, this can lead to falling fuel prices, which in turn can lead to an increase in demand.
• Moral Hazard Effect - More energy-efficient and therefore ecologically more sustainable products and services often have a symbolic meaning. For example, the purchase of a product previously considered to be harmful to the environment is suddenly justified by efficiency gains and the resulting lower energy consumption.
• Moral Leaking Effect - A slight modification of the behavioral psychological effects is the moral leaking effect. Thus, the increased consumption of the product or service after the increase in efficiency can not only be done actively and deliberately, but also unconsciously. After installing an energy-efficient heating system, less attention is paid to the correct ventilation technology and the windows remain tilted even during the heating season. (direct rebound effect)
• Moral Licensing Effect - If the consumption of an energy-efficient product leads to the demand for other non-efficient products, it is said that it has a moral licensing effect. The purchase of a fuel-efficient vehicle justifies for consumers, for example, a long-distance trip that is made by plane. (Indirect rebound effect)
• Time Rebound - Frequently observed is a time-rebound: Faster traffic connections mean that additional distances are covered; Time-saving household appliances such as washing machines change the standards (it is more washed, etc.).
• Risk Rebound - In traffic and occupational psychology, rebound is known as risk compensation: anyone who feels safer with a harness, airbag and ABS, with a bicycle helmet or as a result of occupational safety measures, tends to be more risky or have to reckon with riskier actions by others ,
  Source: Study "Demand-to-the-technology-to-inhibit-the-rebound-effect"

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