Clothes dryer

This article explains the electric clothes dryer. For other types of clothes dryers, see clothesline , clothes horse and clothes dryer .

Exhaust air dryer

A tumble dryer is a household appliance that is used to machine- dry moist textiles in a short time with the supply of warm air . Standard devices are shaped and sized like a fully automatic washing machine and are often simply called dryers . Devices that combine the washing and drying functions in one device are called washer-dryers .

Tumble-drier are in Switzerland after the English expression tumble dryer as Tumbler referred. In Hamburg the term bottlenose dolphin is also used, the Low German equivalent of the English "tumbler".

history

The first hand-operated tumble dryer was invented by M. Pochon from France as early as 1800. The first electric clothes dryer hit the market in the early 20th century. In the 1940s, industrial designer Brooks Stevens designed the first tumble dryer with a glass window. The first European tumble dryer was developed by Miele in 1958 . However, these devices were initially rarely used in private households, as the laundry was usually hung up to dry in the traditional way, for which many houses had their own drying rooms (mostly in the attic ) or clotheslines outdoors. It was not until the 1980s that tumble dryers were increasingly used in private households in Europe. The reason for this was, on the one hand, changed lifestyles (due to the increasing employment of women, the time saved by the tumble dryer was welcome, while the classic housewife was able to spare the time to hang up and hang up the laundry), on the other hand, the drying rooms in many apartment buildings increasingly disappeared in favor of living space.

To date, only the design and other functions of the tumble dryer have changed, but the basic principle has remained unchanged.

Physics of drying

In order to dry laundry, the water should first be removed mechanically. A spin dryer reduces the amount of water to 30 to 50% of the dry weight of the laundry, depending on the number of revolutions and drum size. Higher degrees of drying are difficult to achieve in this way because the water is bound to the fibers by capillary action.

The subsequent drying by evaporating the water is energy-intensive. The evaporation of 1 kg of water with an initial temperature of 25 ° C requires 2600 kJ or 0.73 kWh. Drying 1 kg of laundry with a residual moisture of 60% requires approx. 0.5 kWh. A heat recovery from the water vapor, e.g. B. in models with a heat pump , is technically more complex, but saves up to 50% electrical energy.

To dry 6 kg of laundry in one wash cycle in a simple tumble dryer, around 3 kWh of energy must be used. At an energy price of 0.30 € / kWh, drying 6 kg of damp laundry costs around 0.90 €.

Self-ignition of laundry

Vegetable oils or animal fats can catch fire due to spontaneous combustion if laundry is improperly cleaned and heated at temperatures above 70 ° Celsius . When using tumble dryers, there is an increased risk of these processes, which can quickly lead to a fire in the entire device.

Dryer types

Drum dryer

The laundry to be dried is in a horizontally rotating drum. As a result, the laundry is constantly circulated and a large effective surface of the laundry is achieved.

Warmed air flows along the drum rotation axis through the damp laundry towards the door. The dry, warm air is able to absorb the moisture from the laundry up to the saturation limit. After the moist air has passed a lint filter , it is - depending on the model - dried by condensation or blown outdoors.

In contrast to washing machines, dryers often do not have a transparent window in the front door. But there are also devices with a transparent loading hatch and even with interior lighting so that the laundry can be observed while it is drying.

Exhaust air dryer

An exhaust air dryer leads the moist air z. B. via an exhaust hose or a permanently installed line to the outside. In addition to the moisture, fine fluff is also removed. So that the back pressure is not increased unnecessarily, the exhaust air line has a diameter of 10 cm, the line length is usually less than 3 meters. A slight slope of around 2 ° towards the outlet is recommended so that condensation does not remain in the exhaust air line. If there are fireplaces (ovens, boilers, gas boilers) in the installation room or in adjoining rooms, the slight negative pressure that the tumble dryer generates in the room can prevent the fireplaces from drawing, so there is a risk of poisoning from exhaust gases. It must then be ensured (e.g. by a window that is open a gap) that supply air can flow in from the outside so that there is no negative pressure in the room. The dryer will also work better then. Little is known that even a slight negative pressure in buildings can suck in the radioactive gas radon from the ground, which leads to increased radiation exposure.

Capacitor box

Various external condenser boxes are available so that exhaust air dryers can also be operated in closed rooms. These are connected to the exhaust air hose and are intended to cool the air and collect the condensed water. However, this can only work efficiently with cooling if the device is not installed in a cool cellar. Some models use water or ice packs for this purpose , which must first be frozen in the refrigerator . This eliminates the need for energy-saving considerations to connect such boxes only to keep the heat from the exhaust air in the room in winter.

Condensation dryer

Removable condenser with lint from a condensation dryer.

In the case of condensation dryers, the air inside the dryer is in a largely closed circuit. The initially cool circulating air is heated, which reduces the relative humidity (warm air can absorb more moisture than cold air). This dry, warm air is blown through the damp laundry, which is circulated in a drum, and absorbs the moisture through evaporation. The condenser located under the drum has the task of removing the moisture from the air around the machine. To do this, the warm, humid air is cooled. A fan coupled to the drum motor conveys cool ambient air through the condenser and cools the warm, humid machine air flowing spatially separated through metal sheets through metallic heat conduction. The condenser falls below the dew point and the excess moisture condenses as liquid water, which initially collects in a downstream tub. The cooled circulating air is then warmed up again and the circuit is closed. The ambient air heated when flowing through the condenser is discharged into the surrounding space; it cannot be used for reheating because of the lower temperature level. These "air-cooled" dryers work better the cooler the room in which they are installed.

The condensed water is pumped by a cyclically working pump into a container, usually located next to the control panel, which must be emptied regularly. Optionally, a condensation dryer can also be connected to an existing waste water connection via a hose. For this purpose, a separable hose connection is usually provided on the rear of the device.

Fine fluff is deposited in the condenser and limits its efficiency. Furthermore, such devices require a little more energy than exhaust air dryers (~ 10%); In contrast to this, however, the energy is not diverted into the open air, but given off as heat to the installation room. This is an advantage for installation in living rooms in winter, as it saves heating energy, whereas in summer it is more of a disadvantage.

Condensation dryers are independent of an outlet (wall opening or similar) for the exhaust air hose. They are more expensive to buy than an exhaust air dryer.

The measured energy demand is, for example, a Siemens S46.51 equipped with 6 T-shirts and 4 pants, cupboard dry at 2.4 kWh.

Conventional devices that are ready for the market currently only achieve energy efficiency class B. Different strict evaluation criteria apply to exhaust air dryers and condensation dryers; it happens that a condensation dryer, the energy-efficiency class B for the same amount of washing requires more power than an exhaust air dryer, the energy-efficiency class C .

Dryer with heat pump

There are condensation dryers that contain a heat pump . Their market share was 22 percent in 2011 (2010: 14 percent).

Tumble dryer with heat pump

As with the condenser dryer, the fan conveys dry, preheated process air in a closed circuit through the laundry drum and the damp laundry it contains. As with the condenser dryer, the advantage of a closed process air circuit is that the ambient air in the installation room (e.g. laundry room) is not humidified. The ambient air in the room only warms up slightly. Just like a condenser dryer, a tumble dryer with a heat pump does not require an exhaust air connection. As with other dryers, the water in the laundry evaporates from the air blown through the laundry and is absorbed by it. The air cools down by absorbing water and becomes humid. It then flows into the evaporator of the heat pump (cold side), where it is cooled significantly below the dew point . As a result, the water vapor condenses on the cold surface of the evaporator. In this way the air is partially dehumidified. The liquid water is drained and collected. In the evaporator, a heat flow is transferred to the refrigerant in the heat pump, which then evaporates. The cold, dehumidified process air then flows into the condenser of the heat pump (warm side), in which it is heated. In the condenser, the heat flow from the compressed refrigerant is transferred to the process air and the refrigerant is condensed. The heated, dry air is in turn fed into the laundry drum. ${\displaystyle {\dot {Q}}_{V}}$ ${\displaystyle {\dot {Q}}_{K}}$

Functional diagram of a tumble dryer with heat pump: 1 condenser, 2 expansion device, 3 evaporator, 4 compressor (compressor), 5 process air fan, 6 laundry drum with laundry

Heat pump unit of a tumble dryer

${\displaystyle {\dot {Q}}_{V}+P={\dot {Q}}_{K}}$

The main advantage is the energy saving. Electrical power is necessary for the operation of the heat pump's compressor, but the heat output generated is higher than this by the amount of the recovered condensation heat . Further power is required for the process air fan and for the drum drive, but this is comparatively low. ${\displaystyle P}$ ${\displaystyle {\dot {Q}}_{K}}$

Such energy-efficient devices with a development status from 2014 correspond to energy efficiency class A and better. The energy efficiency class A corresponds to an electrical energy requirement of 0.55 kWh / kg of dry laundry. Compared to conventional condenser dryers of energy efficiency class B, a tumble dryer with a heat pump saves more than 50% energy. A heat pump condenser dryer, for example, consumes around 0.22 kWh / kg of wet laundry. Due to legal regulations, since January 1, 2012, only A-class devices for drying laundry with mains operation may be sold in Switzerland. The term heat pump dryer has established itself among household appliance manufacturers .

Dryers with heat pumps are more expensive to purchase, but significantly cheaper in terms of total costs (including electricity). In its test, the Stiftung Warentest calculated total costs of a good 860 to 1,150 euros over 10 years of use, compared to around 1,030 to 1,430 euros for conventional dryers.

The drying time is usually longer than for devices with electric heating; a full drum is often cupboard dry only after more than two hours. The laundry temperature is often lower than 60 ° C, which is both gentle and non-sterilizing.

Dryer with heat from the house heating

Here, dryers are supplied with the necessary warm air via a heat exchanger connected to the heating line of the central heating system. The current retrofit solution is an encapsulated radiator or heat exchanger that is connected to the airway of the dryer via corrugated pipes . Instead of the electrical heater built into the dryer, the hot water flow of the connected hot water heater is switched on and off. Whether this type of construction is more environmentally friendly or more energy efficient than direct electric heating depends on how environmentally friendly and economical the connected central heating is. Operation with solar heat is also possible and further reduces operating costs. A market launch as an integrated unit was planned for spring 2009, but Miele did not take place until mid-2013. The solution of this first market-ready system provides for the integration into a heating system with a storage tank in layers. Water is taken from the upper, warmer layers of the storage tank and passed through a heat exchanger in the process air flow, which heats the air. The water is fed back into the storage tank. After the air has flowed through the drum and dehumidified the laundry, a second heat exchanger is used as a condenser, similar to the process of a heat pump dryer, in order to be able to reuse the energy from the process air. This 2nd heat exchanger is cooled with water from the lower area of ​​the stratified storage tank, which is also fed back into the storage tank. If the temperature of the cooling water is too high, an additional desuperheating module, which is electronically linked to the control of the device, is switched on. This module, which is attached to a wall near the dryer, is in itself a third, large heat exchanger that releases the excess energy of the cooling water into the room air. The fact that there is a closed water cycle and as much heat as possible is recovered means that energy consumption is even lower than that of the most economical heat pump dryers. Due to the complicated technology and complex installation, however, both acquisition and installation costs are far above the price level of energy-efficient tumble dryers.

Gas heated dryer

In Europe, dryers that are heated with gas are relatively rare. The purchase prices are usually higher, but the energy efficiency is better than that of electrical devices. Gas providers occasionally subsidize their purchase. This version is more common in Anglo-American countries.

Washer dryer

Washer-dryer Softtronic WT 2670 from Miele

A washer-dryer is a combination of a dryer and a fully automatic washing machine in one device.

Because the laundry needs more space in the drum when drying than when washing, usually only half a load of laundry can be dried; you must therefore remove some of the laundry after the wash cycle and, if necessary, dry it later in a second drying cycle.

Devices are available that can dry a load of laundry in one go. Often, however, this only works with small fill quantities, which greatly increases electricity and water consumption. Due to their principle, these devices also need a very long time for a complete cycle, typically five to six hours with five kg of dry laundry. However, they are space-saving as only one device is required instead of two.

Washer-dryers are usually built without a fluff filter and use cold fresh water to condense the warm, humid circulating air; therefore they also consume water for drying. Compared to two individual devices, the operating costs are higher. However, since 2010 there have been washer-dryers on the market that manage without the increased water consumption during drying, but dry the laundry like heat pump dryers. The construction of the devices is more similar to the washing machine and is therefore also available as a front or top loader.

Drying cabinet

Drying cabinet

Open drying cabinet

Textile care system - laundry drying cabinet with heat pump

An alternative to the drum dryer is the drying cabinet with a built-in fan that works on the exhaust air dryer principle. Here the laundry is hung up in a chamber into which cold or warm air is blown. The drying cabinet is very economical in cold air mode, whereas warm air mode (with heating) uses significantly more electricity than comparable drum dryers. There are also drying cabinets that work according to the condensation dryer principle.

There are also drying cabinets that work according to the heat pump principle and thereby significantly reduce the energy consumption in hot air operation compared to purely electrical heating. The conditioning of the air, i.e. H. Heating and cooling are the same as for a dryer with a heat pump .

Depending on the design, such drying cabinets offer additional main functions for treating laundry such as freshening up with steam and photocatalysis (breaking down odor molecules), de-creasing, sanitizing and drying. Such multi-functional devices are also referred to as textile care systems.

Indoor air tumble dryer

Indoor air tumble dryer

Built-in Secomat in a wet room

The room air dryer is used to dry laundry in communal laundry rooms , especially in Switzerland . In Switzerland, the air dryer is often known as "Secomat", although it is just a brand name. When mounted on the wall, the device blows a stream of dry air into the laundry hanging on the linen. The drying device works on the principle of the heat pump . It sucks in the moist air and the moisture it contains condenses on the cold surface of the heat pump's evaporator. The heat energy dissipated in the condenser of the heat pump is used to reheat the cooled and dehumidified air, which is then returned to the drying room. This warm air then absorbs water from the laundry again due to evaporation. The condensate that forms in the evaporator is collected or discharged directly into the sewer system. The room air tumble dryer switches off automatically as soon as the humidity sensor signals that the humidity of the air corresponds to the desired level. Since neither mechanical forces nor high temperatures of the drying air act on the laundry, all textiles can be dried. Sports equipment such as hockey equipment or tents can also be dried in this way. A positive side effect is the simultaneous dehumidification of the building fabric. Modern room air tumble dryers therefore have an electronic control. This allows different operating modes to use the room air dryer (for example in a new building) as a room air dehumidifier. This means that mold formation in the drying room can be prevented or prevented.

As, contrary to other drying methods, the laundry is not dried with heat, room air tumble dryers are extremely energy efficient. In order to be able to compare the various providers, we developed our own test methods. The association for the promotion of room air tumble dryers VRWT marks the most energy-efficient devices with the label "Qualidryer" on behalf of the Federal Office for Energy in Switzerland. In Switzerland, the purchase of a room air dryer is even rewarded with direct payments from various energy suppliers.

Alternatives to the tumble dryer

In households with a garden or balcony, linen can often be dried outdoors (especially under a canopy in changeable weather), which can save energy. The laundry dries quickly in direct sunlight and / or in wind. The UV rays contained in sunlight disinfect the laundry (if there are any microorganisms on the laundry after washing) and bleach it (this is desirable for white laundry; it may be undesirable for colored laundry). Line drying is considered to be more gentle on clothes compared to drum dryers, as fiber ends "break off" in the dryer.

Line drying in a loft / attic uses the relatively warm and dry air that is often present there. However, since many attics that were previously used to dry clothes have now been converted into residential purposes, this option is now missing in many houses. Another possibility is to dry the lines in a special drying room (for example a former laundry room) with a powerful electric fan that diverts the moist air into the open. Assuming that a suitable room is available, the investment and operating costs are low.

However, the line drying is not always possible: In poorly ventilated attics (for example, if a. Thermal insulation of the roof is available) or often in just such laundering cellars laundry dries in the autumn and winter after several days or weeks; rooms and masonry may be damaged by the moisture. It is also not advisable to hang up laundry in heated living spaces if these have low air exchange rates; the moisture must then be removed by increased, very extensive ventilation, which u. U. even more heating energy is lost than an electric dryer would consume. It is true that an exhaust air dryer blows room air and the heating energy it contains into the open air if it is installed in a heated room; but at least it does not moisten the installation room. In the case of already high air exchange rates, hanging up the laundry can save energy, as you may save yourself a humidifier . If in doubt, the humidity can be checked with a hygrometer .

Some particularly tightly woven or thick items of laundry (e.g. extra thick towels or shower rugs) can only be completely dry outdoors under particularly favorable conditions.

The demonstrably erroneous idea that houses have breathing walls goes back to a measurement error in the 19th century. Only negligibly small amounts of moisture can diffuse into the open air through an external wall. At most, leaky window frames can be air-permeable.

Household practice and service

Not all textiles can be dried in the drum dryer. Synthetics, wool and silk can be damaged; vegetable fibers can shrink. Knitwear in particular (especially underwear) tend to shrink. Drum dryers offer at least one normal program and one gentle program (with reduced temperature), furthermore at least one time control, nowadays usually also a control with moisture sensor, which ends the program when the set degree of dryness is reached (e.g. insufficiently damp, ironing damp, cupboard dry, extra dry). If overdrying, knitted fabrics in particular can shrink more and the laundry tends to wrinkle.

Older literature recommends buying underwear that is to be machine dried one size larger than normal. However, it is safer to only buy laundry that has been expressly declared suitable for tumble drying ( care label ).

In some cases, considerable amounts of lint collect in the lint filter, which in the long term can significantly reduce the efficiency of the device. The lint filter is usually emptied by hand after each use. Washer-dryers usually even have a "rinse off lint" program. However, only 10% of the lint is caused by machine drying; the remaining 90% is already rubbed off by wearing and washing.

The more thoroughly the laundry was spun, the faster and more energy-saving the subsequent drying process. Additional spinning uses significantly less energy than achieving the same degree of drying in the dryer.

Laundry from the dryer is very soft and fluffy even without fabric softener, and some textiles even do not need to be ironed. Pet owners particularly appreciate the fact that exhaust air dryers remove pet hair quite well.

In contrast to drum dryers, room air tumble dryers and drying cabinets are suitable for all textiles, including those that are actually not allowed to be machine dried.

Dryer balls

• 

  Tennis ball in the tumble dryer

• 

  Dryer balls, shape similar to hedgehog ball

When drying down in down jackets or down sleeping bags , we recommend adding several tennis balls to the tumble dryer.

Balls with knobs are available in stores, which, when added to the laundry in pairs, are intended to accelerate the drying process. According to the provider, the moving balls loosen the laundry so that the air has more contact surface. In addition, the laundry should be made even softer by the balls.

Power consumption

The total power consumption (washing machine plus tumble dryer) can be reduced by selecting a high spin speed (e.g. 1400 revolutions per minute). The spin efficiency class of washing machines with 1400 / min. is only 'B' (residual moisture 45 to <54 percent). Washing machines with 1600 / min. only have a little less residual moisture; those with less than 45% residual moisture have spin efficiency class A. A higher speed above all causes more creases; the marginal utility is marginal.

Tumble dryers have been criticized for their often high power consumption, which many people could avoid by conventional drying (see: Alternatives to tumble dryers ).

Energy labels are mandatory in the EU. They provide information about power consumption and energy efficiency and bring about a certain degree of market transparency . Up to May 29, 2013 there were energy efficiency classes A to G; since that date there has been a new EU energy label showing additional energy efficiency classes. The best category is now A +++, the lowest energy efficiency class corresponds to class D. From November 2013, all new appliances in retail must at least meet the requirements of energy efficiency class C, from November 2015 those of energy efficiency class B. Class A +++ dryers consume around 70 percent less electricity than a class B device. The higher purchase price for a more efficient class of device pays off after a certain number of operating hours.

In 2007, the US government's energy information agency calculated that tumble dryers account for six percent of the electricity consumed by American households. Tumble dryers are more common in the US than in Europe; In some areas of the United States, drying laundry outdoors is considered a sign of poverty or antisociality . In some neighborhoods or cities in the United States it was or is even prohibited.

Equipment quota

The Federal Statistical Office shows an equipment quota of 38.6 percent for private households in Germany for 2009. On January 1, 2011, 39.7 percent of households had at least one tumble dryer. In 2019 the rate rose to 42.6%. In 2010, sales of tumble dryers in Germany amounted to 495 million euros.

See also

• Care symbol for drying

literature

• Jens Uetrecht: Successfully repairing large electrical appliances yourself. How to repair washing machines, tumble dryers, dishwashers, electric stoves, extractor hoods, refrigerators, microwave ovens. In: Do it yourself. Volume 16. Franzis, Feldkirchen 1997, ISBN 3-7723-4082-2 .
• Günter E. Wegner: Electrical household appliances: technology and service. 3rd, revised and expanded edition. Hüthig & Pflaum, Munich / Heidelberg 2008, ISBN 978-3-8101-0254-6 .

Web links

Commons : Clothes dryer  - collection of images, videos, and audio files

Wiktionary: clothes dryer  - explanations of meanings, word origins, synonyms, translations

• Tumble dryer test by Stiftung Warentest , test 1/2012 (subject to a charge)
• Dewatering and drying laundry at hauswirtschaft.info, accessed on April 13, 2014

Individual evidence

1. ↑ SuperSlang.de www.superslang.de , accessed on September 29, 2013.
2. ↑ Source: Development of the first tumble dryer with a glass window
3. ↑ Self-ignition of laundry - fats and oils are to blame , Vorarlberg Fire Prevention Office, accessed on August 8, 2018
4. ↑ Self-ignition of laundry , Hetzel laundry machines, accessed on August 8, 2018
5. ↑ Federal Office for Radiation Protection [1] (PDF; 1.3 MB) www.bfs.de, accessed on April 9, 2017
6. ↑ ^{a b} Dryer test by Stiftung Warentest , test 1/2012 and test.de , accessed on January 3, 2015
7. ↑ Waschtest.net Comparison of Different dryer technologies. Retrieved September 20, 2016 . 
8. ↑ Energy Ordinance (EnV). Retrieved March 11, 2015 . 
9. ↑ Product selection dryer. Retrieved March 11, 2015 . 
10. ↑ Heat pump dryer. (No longer available online.) Archived from the original on August 15, 2014 ; accessed on March 11, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
11. ↑ Fast, gentle & economical - the new Adora heat pump dryers. Retrieved March 11, 2015 . 
12. ↑ Dryers with heat pumps are more economical and better. In: Stiftung Warentest . Retrieved October 7, 2013 . 
13. ↑ [2]
14. ↑ Dirk Asendorpf: Trendy technology: hot air . In: Die ZEIT . No. 38 , September 10, 2009, pp. 40 ( zeit.de ). www.zeit.de, accessed on January 3, 2015
15. ↑ “Refresh-Butler” textile care system. Retrieved March 11, 2015 . 
16. ↑ V-ZUG AG: Flyer textile care system "Refresh Butler" . 2013.
17. ↑ www.vrwt.ch, Association for the Promotion of Indoor Air Tumble Dryers .
18. ↑ www.topten.ch, Funding programs for energy suppliers www.topten.ch, accessed on January 3, 2015
19. ↑ ^{a b} Tips for drying , test.de , accessed on September 30, 2014
20. ↑ What must never be put in the dryer. In: T-Online. February 28, 2014, accessed February 17, 2018 . 
21. ↑ Put tennis balls in the dryer with the down coat. In: FOCUS Online. January 22, 2013, accessed April 9, 2016 . 
22. ^ IKW: Questions and answers about washing and drying. In: www.ikw.org (Association of Toiletries and Detergents ). Retrieved April 9, 2016 . 
23. ↑ Washing the sleeping bag: This must be taken into account when taking care of it. In: Bergzeit Magazin. January 20, 2015, accessed April 9, 2016 . 
24. ↑ According to a test by the 'Verein für Konsumenteninformation' published in ' KONSUMENT 1/2012' December 30, 2011 [3] 1,400 spinning tours per minute are sufficient.
25. ↑ dena.de: New energy label for tumble dryers ( memento of the original from August 25, 2013 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. www.dena.de, accessed on January 3, 2015 
26. ↑ www.stromeffektiven.de: Top devices database ( memento of the original from June 30, 2013 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. www.dena.de, accessed on January 3, 2015 
27. ↑ ^{a b} Nikolaus Piper: Now the neighbors are doing their laundry. A grotesque argument has broken out in the United States about whether you can hang your clothes out to dry in the garden . In: Süddeutsche Zeitung . October 1, 2007 ( sueddeutsche.de [accessed October 1, 2007]).
28. ↑ Statistical Yearbook 2012, p. 174.
29. ↑ https://de.statista.com/statistik/daten/studie/516868/umfrage/private-haushalte-in-deutschland-mit-waeschetrock/#:~:text=Rund%2042%2C6%20Prozent%20der,im % 20year% 202019% 20a% 20W% C3% A4 dryer
30. ↑ Statistica.com: Household Appliances . Retrieved February 9, 2013.