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It's about tempting efficiency gains

What do apples have to do with the energy transition? Quite a lot. For instance, say one kilo of apples is on special offer. If you buy two kilos, you may realise only later that less money is left in your purse. It appears rather paradoxical, doesn't it? You wanted to save money, but you ended up spending more. Can the same happen when we want to save energy? And if so, why?

The answer is the 'rebound effect'. It means that cost savings due to energy efficiency make consumers demand more energy - and thus de facto reduce energy efficiency gains. A special offer for apples, for instance, makes consumers buy more.

More energy efficiency, the same energy consumption?

Of course, we must not compare apples with oranges. But there is a parallel between apple pies and energy-saving light bulbs. Energy-saving light bulbs may cause us to switch off the light later in the evening than conventional light bulbs. Freezers are another example: there can be no doubt that energy-efficient appliances need less electricity. However, if consumers buy larger or additional freezers, the efficiency gains are lost. Cars today also need less fuel per unit of horsepower than some years ago - but there are more high-power cars on the roads than there used to be. If fuel consumption falls per kilometre driven, the cost of the car is reduced - but this increases the incentive to use the car more often.

This is relatively easy to understand at the level of private households, but it has entirely different dimensions for an economy with millions of people. This is why we must bear in mind the rebound effect in connection with the energy transition and the related increase in energy efficiency.

Energy efficiency strategy: we must not lose sight of the rebound effect

The rebound effect of course must not prevent us from making efforts to save energy. Increasing energy efficiency is important to reduce the number of inefficient appliances. But we must also save energy and make use of efficiency potentials in a targeted way. Germany aims to reduce primary energy consumption by 20 per cent by 2020 compared with 2008 and by 50 per cent by 2050. The National Action Plan on Energy Efficiency (NAPE) sets out the federal government's strategy to reach this objective and to increase overall energy efficiency. The Federal Ministry for Economic Affairs and Energy is elaborating further approaches to improve energy efficiency - which also take account of the rebound effect. The new approaches are to be published in a "Green Paper on Energy Efficiency" and be subject to public consultation this year.