The article compares the energy savings over an already inefficient dryer. The article mentions that an existing dryer takes 50min (average). Such dryers are not what anyone should buy, they waste too much energy. Over time it's cheaper to buy a heat pump dryer. Those easily take 2.5 hours to dry. They're significantly cheaper over an e.g. 5-10 year period than buying a cheaper and way more inefficient dryer.

The links to more detail with: > The goal of this project is to develop a clothes dryer prototype, using ultrasonic transducers, with an EF above 10 lb/kWh.

But also: > DOE’s Building Technologies Office is seeking new clothes dryer technologies that can increase the energy factor (EF) from 3.7 to 5.43 lb/kWh

However, a quick Google shows that the 3.7 is not a heat pump dryer, see e.g. https://www.intechopen.com/books/current-drying-processes/th.... The figure for an existing dryer should be 7.6 lb/kWh. Meaning, the solution is (currently) not good enough.

The link in the article and my link shows that the intend is to go way over 10 lb/kWh. The link I found showed it could be around 20 or even 44 lb/kWh (seems to depend on the frequency used). This while being way quicker than anything else, especially heat pump dryers.

Or microwaves?

(Better not leave anything metallic in there though...)