Back in my AC installation days we had two voltage choices to make when ordering AC units. 208V or 220V. As a general rule 208v came from underground service and 220 came from overhead service lines. There was a buck or boost transformer available if you had a 220 unit and only 208 power available and I think vice or versa. There is an RV supplier that sells this type of transformer for boosting power in a low power RV hookup. Mr. Gary D will have to bail me out on these revelations. I'm not sure what voltage our AC units will operate down to without damage.
Harry
Shirley & Harry / 2000 Liberty / 2008 GMC Envoy Denali