How can this be? Washing longer saves energy

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Modern washing machines need significantly more time per wash cycle than old models. The longer the machine washes, the more electricity it consumes – or does it?? BAYERN 1 environment commissioner investigates the contradiction.

By: alexander dallmus

Status: 21.05.2017 | archive

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Can it make environmental sense? Modern washing machines with the energy efficiency class A+++ need more than two and a half hours for a load of 40-degree laundry. It consumes more electricity than older machines that take almost two hours to wash the same load, you might think. But washing depends on four factors, and time is only one of them.

Four factors determine the washing result

  • Detergent
  • Mechanics (condition of the washing drum, how does it move), . )
  • temperature
  • Time

If one of the four factors is changed, this affects the other three.

Washing machine manufacturers have no influence on the effect of detergents. The mechanics are already very sophisticated, and energy consumption can hardly be improved any further. "the potential to save even more energy with even better mechanics is very small", explains werner scholz. He is responsible for the electrical household appliances sector at the German Electrical and Electronic Manufacturers’ Association (ZVEI).


Heating the water consumes the most energy, but even here the margins are limited. The washing temperature cannot be lowered at will, because otherwise the detergents will no longer work properly. Detergents contain enzymes, for example, which only take effect at certain temperatures.

For hygienic reasons, the washing temperature should not be below 40 degrees Celsius. Many germs survive otherwise. For normally soiled laundry, 40 degrees is sufficient; for heavily soiled laundry, 60 degrees is sufficient. To kill germs in the machine, washing should be done at 60 degrees once a month. The 95-degree wash is an exception nowadays.

Connecting the washing machine to the hot water supply?

Whether it is worthwhile to connect the washing machine to the hot water supply depends on several factors. How the hot water is heated is important. It could be worthwhile with modern condensing boilers, a heat pump or a solar system. However, the washing machine must also be equipped for this purpose. Whether the connection is financially viable, for example because new pipes have to be laid, must be checked in each individual case.

The washing result depends to a large extent on how long a wash cycle takes. In recent years, washing programs have become longer and longer to ensure that laundry is as clean as it used to be, when programs were shorter but used more energy. a long wash cycle consumes less energy than a short one.

"This contradiction can be explained using the example of driving a car: if you drive a distance of 100 kilometers at a speed of 100 km/h, you need significantly more fuel than if you drive at a speed of 50 km/h for the same distance. But the drive takes longer."

Werner Scholz, German Electrical and Electronic Manufacturers’ Association (ZVEI)

Facts about washing

  • Four kilograms of laundry per person per week in germany.
  • Washing consumes around six billion kilowatt hours of electricity and 330 million cubic meters of water per year.
  • A new washing machine, with average use, consumes almost 30.000 liters of water, 200 kilowatt hours of electricity and nine kilograms of detergent less than one machine 25 years ago.
  • Despite lower energy consumption, modern washing machines have a higher washing performance than old models: today’s 40-degree wash is comparable to the 60-degree wash.
  • Energy can be saved mainly by lowering the water temperature. Rotating the drum consumes comparatively little electricity.
  • The longer washing time improves the washing result at low temperature and saves up to 50 percent energy.
  • A two-person household saves the environment at a low washing temperature by approx. 33 kilograms less CO2 emissions per year (source: university of bonn, household technology)

Comparison: old and new washing machines

  • A 15-year-old washing machine costs 75 euros more per year in a four-person household.
  • A 15-year-old washing machine consumes twice as much energy and water as a modern machine.
  • A 30-year-old machine consumes four times as much energy and water as a modern one.


Patience when doing laundry pays off – for the environment and your wallet.

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