Heat pump tumble dryers: Eco-friendly or not?
Posted by Alex Barrett on 20 October 2016 at 9:45 am
It is no secret that tumble dryers are not especially environmentally friendly. They use quite a lot of energy and are certainly less energy efficient than hanging your washing out to dry.
Several types of dryer claim to be more environmentally friendly. In particular heat pump tumble dryers recycle heat to cut the energy costs of running the device. But does this make them better for the environment. Clearly using an electrical appliance is never going to be as environmentally friendly as not using one. But how do these new dryers compare to the more conventional sort?
How does a tumble dryer work?
A tumble dryer works by heating up the contents, so that water in the clothes evaporates into the air. This wet air is then removed from the dryer to be replaced with more warm, dry air from the fan and heater. This process repeats until the clothes are completely dry. What makes a dryer more or less environmentally friendly largely comes down to how efficiently it uses this heat, and what it does with the waste air. Some dryers vent the wet air to the outside of the house. This prevents it from making the room very humid and potentially causing damp. However it does mean that heat is being produced, only to be dumped outside, when it could contribute towards space heating.
Condensing tumble dryers
Condensing tumble dryers offer a better solution. The warm, wet air from the drum is cooled, so that the water condenses out and is captured in a tank. This means that the heat can be released into the room through the machine, rather than being pumped out of the house. Heat pump tumble dryers claim to make this process more efficient. Rather than venting hot air to the room after the water has been extracted they use a heat pump to retain that heat, and use it to warm up the fresh air being introduced to the dryer.
Some heat will be lost in the recycling process, and of course the air still has to be warmed up initially, but nonetheless a lot less energy is needed to maintain a constant high temperature.
Heat pump tumble dryers - pros and cons
Heat pump tumble dryers work at a lower temperature than conventional ones, so they do use a lot less energy than a regular dryer does.
Manufacturers of heat pump tumble dryers claim that the reduction in energy use, and thus the cost of using the device is substantial. Energy savings are reported to be in the range of 40-60% [1, 2]. However the initial cost of the device is much higher so it is likely that you would have to run a tumble dryer very frequently to recover the cost of buying one.
A downside is that it can take longer to dry clothes. Beko, one manufacturer of these devices, claim that their machines take only five minutes longer than a regular dryer . However a review by UK White Goods claims that these devices take up to twice as long to run . They have raised concerns that the cooler temperature and additional running time mean that any energy saving will be cancelled out by the length of time for which it needs to be run.
They argue that these appliances will rarely be used in ideal circumstances. To get the short reported running times you will have to be very rigorous in keeping filters clean and well maintained. This is something which is easy for the manufacturers to do in their tests, but most users will not take as good care of their machines.
UK White Goods are also concerned about the additional cost of these devices in terms of embodied energy. They cost more to manufacture, and transport. Which they feel counteracts the green credentials of these devices. Do independent tests back up Beko’s estimates of the device’s energy savings?
A report by Which? Magazine states that “the most efficient model we’ve seen costs less than £25 a year to run. Compared to £77, the average running cost of a standard condenser dryer” . This is a pretty good saving, and is comparable to the claims Beko make for their machines. However given the high initial cost of these devices it might not be enough to pay for the cost of the appliance during its lifetime. The Energy Saving Trust do recommend them, although they do advise that everyone use a washing line whenever they can .
So are these devices a good investment despite their high cost? The answer is that it will depend on how much you use your tumble dryer.
If you only use your dryer occasionally, or for very light loads then it may not pay back. However if you do a lot of washing, or run dryers commercially then there is a much better chance that you will find this to be a good investment.
Image Credit: Beko, illustration of a heat pump tumble dryer.
More information about low energy appliances on YouGen.
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