Heat Pumbling Dryer: The functioning

When it comes to ecologically compatible and energy-saving housekeeping, heat pump dryers are often at the top of the list of devices required. This article will tell you in detail how such a heat pump dryer works, what forms the technical basis of this technology and where the advantages and disadvantages of heat pump dryers are.

Heat pump principle

In general, heat pumps work like a refrigerator - only the other way around. If the heat is extracted from air or water by a coolant, this heat can, conversely, be used again for heating.

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A refrigerator also produces waste heat - this is precisely the heat that it extracts from the food that is in it. In theory, you could also use a refrigerator for heating - some grocery stores do just that with their refrigeration systems.

Conversely, the heat in the ambient air can be used to heat a house. If the heat is extracted from the air by a refrigerant, this heat is in turn available for heating.

Application of the heat pump principle to the heat pump dryer

Tumble dryers work on the physical principle that warm air can absorb more moisture than cold air.

If the air inside the heat pump dryer is heated, it absorbs part of the moisture from the cold, wet laundry, much like a blow dryer dries hair by blowing warm air over it.

However, heating air costs a lot of energy. With the heat pump dryer, the exhaust air is therefore passed through a heat pump. The heat is extracted from the exhaust air and reused to heat the cold supply air of the device.

This creates a cycle in which the heat generated once is used again and again. This significantly reduces energy consumption.


When it cools down, the moisture in the air that has been absorbed by the laundry condenses. Since cold air can store less moisture than warm air, the air it contains precipitates as condensate when it cools down.

This condensate is collected in a condensate container. Then it can simply be disposed of or pumped out.

With the heat pump dryer, condensation is even faster than with conventional condensate dryers, as the air is cooled down very quickly by the heat pump. The coolant immediately removes all heat from the warm exhaust air in order to return it to the supply air as completely as possible.

However, this does not mean that the device has a shorter operating time than conventional condensation tumble dryers.

Energy efficiency and cost-benefit ratio of heat pump dryers

According to the results of a study by Stiftung Warentest, heat pump dryers usually require around half the energy that conventional tumble dryers consume. According to the findings of Stiftung Warentest, a dryer charge costs around EUR 1 for a conventional device, but only 40 cents for a heat pump dryer.

But the acquisition costs are also significantly higher. However, the purchase price has already fallen significantly in recent years - the higher purchase costs pay for themselves quickly through the lower power consumption for families and multi-person households.

The higher the energy efficiency class of the device, the greater the difference, of course, and the better the cost-benefit calculation.

When considering a purchase, one should also consider the development of the electricity price over the next few years. Individual forecasts assume further increases in the electricity price to up to 40 cents / kWh by 2020.

Disadvantages of heat pump dryers

Technically, there are no disadvantages of heat pump dryers compared to conventional devices. So far, the only disadvantage is the higher acquisition costs, which do not pay off in all cases (single household, infrequent use).

With most devices that work according to the heat pump principle, you have to reckon with somewhat longer drying times. Since no heating rod is used, the drying time can sometimes be extended to two or three hours.

Advantage: gentle drying of the laundry

On the other hand - due to the lower use of hot air - the fabric of the laundry is also spared compared to conventional dryers. The lifespan of the clothing is thus extended, while frequent use of conventional dryers usually shortens them to a greater or lesser extent.

Heat pump dryer purchase advice

When selecting the devices, both the filling quantity and the energy efficiency class should be the decisive criteria - in connection with the purchase price, of course. Branded devices often have a longer shelf life and a higher energy efficiency class than no-name devices. However, this does not have to apply in all cases.

In any case, make a cost-benefit analysis before buying to see whether the purchase is worthwhile for you, and if so, up to what price.

Tips & Tricks The most ecological and energy-saving option is, of course, to dry the laundry on the line or in a drying room. Often it is just a matter of spending a little time and planning to save a lot of energy here.

If you only have a few items of laundry and want to speed up drying, you can put the wet laundry on a microfibre towel that is as large as possible. After that, roll up the towel as tightly as you can. In this way, a large part of the moisture is pressed out of the laundry. A good microfiber towel is completely dry again just a few minutes later.