Heat Pump Dryers

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The Japanese have had microwave clothes dryers for some time. These use microwaves to heat the wet clothes rather than hot air and by doing so they save approximately 35% in energy consumption. They switch to resistive heating for about the last 10% of the cycle to prevent problems with metal objects. For reasons I am not familiar with these are not available in the United States.

Heat pump dryers are now available in the United States, and these save approximately 65% of the energy consumed by an ordinary dryer. Dryers generally represent around 6% of a households energy consumption, and if you have teenage kids even more. In addition to directly consuming 6% of a households energy budget, dryers also contribute to energy required for heating and/or air conditioning because the air they exhaust to the outside hot came from the inside, and that air will be replaced by cold or hot air from the outside requiring additional energy for heating or cooling the house.

Heat pump dryers cost about $300 more than a conventional resistive heating dryer. Over a ten year lifespan, they will save approximately $1000 in electricity costs assuming the average cost of 8ยข/KWh and average household laundry. The savings will be even greater where the rates are higher or if your household has a higher than average amount of laundry. This is before you factor in heating and air conditioning savings which are even greater.

A heat pump dryer is also more convenient to install, requiring only a drain like a washer and no external vent. In addition a heat pump dryer requires only a standard 120 volt outlet, not the larger 240 volt 30 or 40 amp circuit of a resistive heating dryer.

Instead of heating air, blowing it over clothes, and then exhausting the hot air outdoors and taking fresh air from indoors, a heat pump dryer heats air, passes it over clothes, dehumidifies the air, and passes it over clothes again and again. No air is exhausted outdoors, and liquid water from the dehumidified air is simply drained. Heat energy is not wasted.

Not including the savings in heating and cooling, if everyone switched to heat pump clothes dryers it would save 445 billion KWh of electricity every year, 35 billion dollars in electricity costs each year nation wide. Because our trade deficit, and economic woes, are in large part the result of the energy we import, this would be a very good thing for our domestic economy. Surplus electricity could be used by electric vehicles, or we could burn less natural gas for power generation and instead liquify it and use it to power our vehicles instead of imported oil.

It would reduce the average load on the power grid by 50 megawatts, about 1/10th the output of a medium sized nuclear reactor, but it would reduce the peak load by more than this because most people don’t do clothes at 4AM.

Anything we can do to save energy consumption will allow a larger portion of our energy needs to be satisfied by renewable and environmentally benign sources and less carbon dioxide will be generated as a result.

Don’t get me wrong, I actually like warm weather. It’s the species dying off, cities underwater, desertification of farmland and forest, things that really bothers me. Unfortunately they seem to be an intrinsic part of global warming. A great deal of global warming would be happening without our contribution. We should not accelerate or intensify it further by altering our atmosphere.

Even better than a dryer when weather permits is a clothes line. 100% renewable (solar) powered, no electricity consumption.

Heat Pump dryers are available in Japan and Europe from multiple vendors but like microwave dryers they are not widely available in the United States. One company that does produce a number of heat-pump consumer appliances is Nyle Special Products, and I’ve included a link on the side bar. If anyone knows of other suppliers that make household heat pump dryers available in the United States, please contact me and I will add them.

Category: Future

2 comments on “Heat Pump Dryers

  1. Bosch makes a Heat pump clothes dryer They are called condensing dryers. Their Axxis Series is of this type.

    These dryers sell for about $1,000 or more. They will also save about $1,000 in operating cost over a 10 year period as compared to an electric dryer. Will use about half the electricity of an electric dryer

    Now the bad part. They are much more complicated and have many temperature sensors, humidity sensors, condensate pumps, compressor, refrigerant. Must be much more carefull with filter cleaning, etc. Because these are someonwhat rare; most service personel including ones recomended by Bosch have no idea how to troubleshoot or repair them. You might need to call an HVACR guy to help in troubleshooting problems with these. The Bosch repair guys will charge 200 to 300 to look at it and make small repairs, (of what he thinks is wrong with it).

    Bottom line is you will spend more money on repairs than what energy savings you will get out of it.

    The only advantage to buying one of these “vent free” dryers is if you live in an apartment where there is no place to vent a conventional dryer.

  2. The Bosch WTE86300US Axxis Series dryer is an inefficient old-style condensing dryer without a heat pump. Energy-efficient heat pump clothes dryers are not available in the U.S. due to low energy prices and lack of consumer interest.

    See

    http://en.wikipedia.org/wiki/Clothes_dryer

    for an explanation of the difference between condensing dryers and heat pump dryers.

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