My new dryer is a heat pump. Uses less than half the energy my previous one did. It does take longer to dry clothes, but it's much gentler on the clothes so it's a perfect trade off for me. I'd love to do a heat pump like this for the house but there is so much oil pipeline around me and there's no way a truck with a pile driver can reach my back yard.
We do it. It’s not yet economically worth it but I’ve seen installs. I can’t find it but I saw one that was designed to let a massive shower run continuously with very little heat loss - the water coming out the end of the drain was as cold as the inlet water from the main.
What efficiency are these? Brainstormed this a bit and feels like shower cabins (pretty popular over NE Europe) should have such system as standalone... As in - it collects waste, collects heat and stores it for next shower. Dunno how much energy a typical refrigerant can store tho. Also great fit for Japanese-style smart baths (press a button and water of desired temperature fills and stays warm), tho they seem rare outside Japan.
There are systems that replace the shower drain with something like a heat exchanger, the water is warmed with the drain water right away, no need to store the heat. For example https://www.oeko-energie.de/shop1/de/eco-shower-duschrinne.h... (in German, but the image is simple to understand.)
I think they can recover up to 60-70% of the heat in the drain water. Not bad for totally passive. The installs I have seen are on the main drain for the whole house and located right next to the hot water heater. For it to really work you need a hot water tank, but I have seen some small tanks combined with tankless.
"My new dryer is a heat pump. Uses less than half the energy my previous one did. It does take longer to dry clothes ..."
I used a very modern heat pump dryer in Switzerland all summer and "... longer to dry clothes ..." is an understatement.
A normal, mixed load of clothing took a full 2.5 hours to fully dry.
It reminds me of CF lightbulbs: a failure to solve the real, big problems (efficient and clean generation of electricity) leads to widely distributed pain for end-users (dryers taking hours or terrible, dim, purple lighting).
Far more interesting than hyper optimized electrical loads would be abundant clean energy sources. I would rather have solar panels and free electricity than have utility power and weird, complicated clothes dryers.
... and yes, my analogy is imperfect because the lighting issue was elegantly solved with LEDs. That's unlikely to be the case with clothes dryers, however ...
