I assume they mean washing the clothes in cold water instead of hot. changing the washer’s settings does cunningly mask that the wash will also be less effective.
Numbers: A top loading machine[3] uses about 150 liters (40 gallons) of water to fill. If you fill that with hot water that is water that has had 30°C (50°F)[1] added to it. That is about 20 megajoules (5kWhr). Heating a liter of water from room temperature to vaporization[2] takes 2.5 megajoules (700 watt hours). So… in very rough numbers you can vaporize 8 liters of room temperature water for the same energy it takes to fill a top loading washer once with hot water. I'd say my load of wash doesn't lose 16kg being dried, so I presume less than 8 liters are being vaporized.
[1] I'm pulling numbers out of google here, you didn't expect more than one significant digit, did you?
[2] Vaporization is more than 5 times the energy from 1°C to 99°C.
[3] Terribly inefficient way to wash clothes, but if an article is going to make dramatic statements, you have to figure they will pick the most extreme numbers.
Changing from washing in hot to washing in cold? That's all I can figure. If that is indeed the case one should wash in cold AND line dry their clothes.
"For example, participants estimated that line-drying clothes saves more energy than changing the washer’s settings (the reverse is true)"
Makes no sense to me. "Changing" doesn't mean anything. I'm sure the article is on to something, but that quote here is just too unclear.