@Yuko38 I agree with @Colleen253 . The only reason I can think of that local hosts would choose to put 1 washer/dryers in a single unit is that they have high housekeeping costs. Professional cleaners charge by the hour, and running loads of laundry in succession keeps them there longer, so the absentee hosts figure that they can save money by cutting the changeover time and having enough appliances to do all the laundry at once. Of course there are downsides. For one, those cut corners might also mean a rushed cleaning job. And also, unless the houses were custom-built around this very unconventional home laundry arrangement, there are going to be some bulky appliances awkwardly taking space that could be better filled by features that are more useful and enjoyable to guests or residents.
To answer your question, I guess your calculations are going to have to be based on whether you outsource your housekeeping. It might be useful to have an industrial-grade washer at your disposal if you're running a base cleaning station for multiple units, but if you're offering washer/dryer as an amenity to your guests, you're better off with a normal residential one. A group of up to 8 can generate a lot of laundry, but no more than you make available to them - rather than supplying 80 towels, you can provide a reasonable amount and assume that the longer-staying guests will do a bit of washing during their stay as needed. And that's another consideration: some of your guests will want to use the washer/dryer for their own stuff, but their needs would not justify a more energy-intensive, bulky industrial unit. At the end of the day, you're just running a normal house, not the Motel 6, so I don't see much point in installing different appliances from what the average Mormon family would put in their own houses.
