How to choose between an electric, natural gas, or heat pump clothes dryer?

Question

I will soon be moving into a new home with a very old electric clothes dryer. I expect that before too long it will fail and need replacing. I would like to replace this with a more efficient model. I am considering natural gas, conventional electric (tumble dryer), or heat pump electric.

Which type of dryer will be the most sustainable? I am wondering if others have faced this decision, and how they made their choice.

This answer considers a similar question for home and water heating, but doesn't seem to apply in the case of a clothes dryer. In fact, I thought my question was fairly straightforward, but that answer indicates there may be some issues with heat pump systems.

For context, I live in Wisconsin, where the energy mix for electricity generation is about 30% natural gas, 50% coal, 10% nuclear, and 10% renewable (hydro, wind, and solar).

Answer 1

You need neither a tumble dryer nor a drying cabinet. I haven't used either for years, and we are a two person household in a 36m² studio apartment in England (so winters are rather humid).

By far the most sustainable way to dry clothes is by drying on a line or a clothes horse. Tumble dryers use a lot of energy and damage your clothes. Drying cabinets use a lot of energy. Line drying uses the least energy and does not damage your clothes.

You can either line dry indoors or outdoors.

If you line dry indoors in winter, there is some excess energy usage (unless you are fortunate enough to live in a passive house) because some of your space heating will be end up as latent heat instead.

You can line dry outdoors any time of year (unless it's one of those dreich winter days). See line drying in winter, here or here.

If you have the luxury of a home with more than one room, there is no problem in line drying at all. Just put your clothes horse in a room you are not presently in and make sure the room is well ventilated.

If you have even more luxury of access to a garden or balcony, you can of course dry your clothes there when it's not raining or dreich (crisp -20°C sunny winter days as you get in Wisconsin are totally fine).

Answer 2

I faced the same question with our new home recently. Ultimately I went with a conventional electric dryer.

Whilst the trend in the last couple of decades has been to ridicule/dismiss conventional electric dryers because they are "inefficient", I believe that mentality is simplistic and outdated. The argument only really holds true if your dryer is solely connected to the grid, and grid electricity is expensive and fossil-fuel based. In many cases, not all of those apply. In some cases, none apply — rendering 'efficiency' completely irrelevant.

Since we generally only wash clothes once a week, and have a two-person household, the amount of dryer cycles is relatively low — maybe two per week on average. If the weather permits, we use the outdoor clothes line. If it doesn't, then we use the dryer. About two-thirds of the year we use the outdoor clothes line, so the dryer is only used about a third of the year.

When we consume electricity to dry clothes, the energy comes from a renewable source. We have a decent-sized PV array, and over the long run we generate (far) more power than we use. The inverter is grid-tied so surplus power generation helps 'green the grid' for everyone.

If we time dryer cycles right (e.g. look outside, upwind, and ensure that we have ~30 minutes of blue sky ahead of us) then not only is all the power free, but it doesn't even draw down (wear out) batteries.

Having a conventional electric dryer also means that we benefit from reducing humidity in the house during winter as humid internal air ends up being vented outside.

Conventional dryers are far simpler to manufacture and thus much, much cheaper in this part of the world (compared to the heat pump variety). The money saved is enough to purchase two ~300W solar panels — the output of which generate power bill savings sufficient to replace a conventional electric dryer every two years.

Finally, because they are an old and simple technology, conventional electric dryers seem to last forever. Very little to go wrong. Longer warranties.

So, we went with a conventional electric dryer because, in our situation:

• They are free to operate.
• They are very reliable.
• They are simple to build.
• They are much, much cheaper to purchase.
• The initial savings lets our PV array grow larger, so effectively not only does the first dryer pay for itself in two years, but we effectively get free replacements forever.
• It improves our air quality during winter.

In essence, if you (one day will) have a decent solar setup, then conventional electric dryers require the least amount of resources to construct, are free to acquire, free to operate, last a long time, are free to replace, and can help control humidity.

In our situation, the actual efficiency of the units is completely irrelevant. A 1700W draw for ~30 minutes, twice a week for maybe a third of the year, means absolutely nothing.

PS: The intial savings (made by purchasing a conventional electric dryer instead of a heat pump dryer locally) would pay for ~2640 cycles. That's about 1320 weeks or 77 years at our current rate of use. I don't know how things are in the rest of the world, but in Australia the only people buying heat pump dryers are those that can't do math.

PPS: I have nothing to say about gas dryers. They aren't 'a thing' here. In half a century I've never come across one. I've never known anyone who has owned one. I have never seen one advertised for sale.