depends what you buy, when they first came out they were tiny and you can still buy smaller 2.8cuft ones. they say 4.5cuft is big enough for a family of 4.
now that more companies are making them you can get a Ge profile 5.5cuft or stay with any range of sizes under that.
My buddy said you also change your laundry habits when you have one as you set the delay start and throw a load in before bed and have it timed to finish when you are ready to fold clothes, and his was quite smaller as it was over 10 years ago when he bought it, but even then he said you do smaller loads more often. he actually liked it better as it was less to fold so he would spend 5 min before bed setting it up and loading, then 5 min in the morning folding. he liked it better than sitting around for a day doing laundry once a week.
or you buy the GE profile, spend a little more (pretty close to the price of buying a fancy stacked conventional setup, but its a fancy one)
THIS is the GE Canada website, so don't feint when you see the price, but there is a 2.8cuft and the 5.5 they make. so you can space save and do twice as many loads but with less actual work, or you can get the bigger one and get all the bells and whistles like a smart detergent dispenser that hold enough soap and softener for 32 loads and so on.
the other bonus is they are 120V 15 amp circuits so easy to locate them, and as a bonus your not putting another hole through your rv that you have to maintain