At home, laundry is about removing grease, grass, and coffee stains without damaging the fabric of the clothing. Energy and water efficiency only matter in a secondary sense. Rinse water is plentiful, and the only water quality consideration is that it is sufficiently soft to avoid interference with the detergent and calcium build-up in the clothes.
We think the best bet is the modern keel/centerboard. Unlike centerboards of 20 years ago, the new ones are very efficient going to windward with the boards down and not all that bad with the boards partially raised or withdrawn into a stub keel.