The 39' sailboat has only one unit (16K). In the Hot, Hot, Houston weather, it fights the summer all day long. Barely keeping the boat down to about 72.
On the Mainship, there is 2 and most people with the Aft Cabin have 2 Units. Usually a 16K for the Main Salon and the aft Cabin (master suite) and a smaller one for the Galley and the V-Berth area.
Cruising the Eastern U.S. Inland Waterways and Gulf Coast. Presently on the ICW in Louisiana and heading Back to Texas.