Most (all?) washing machines are 120V. Electric dryers rarely are, because they need a lot more power. I had a small washer/dryer combo unit years ago that used

Most (all?) washing machines are 120V. Electric dryers rarely are, because they need a lot more power. I had a small washer/dryer combo unit years ago that used 120V, and it took about four hours to dry a load that was about half the size of a normal dryer’s capacity. Running both voltages into a house isn’t much of a burden. Residential electricity in the US is two-phase. A 120V circuit pulls from one phase, with the various circuits in your house divided between them to even out the load. A 240V circuit just connects to both phases.