Originally Posted by djmarchand
Conventional marine A/C systems like Cruiseaire are not very efficient. The EER is about 9. SEER may be higher, perhaps 12. But modern inverter driven minisplit A/C systems achieve a SEER of 18 or better.
The DC system that started this thread seems to be about twice as efficient as a Cruiseaire and it might be even better at night when load factors drop. A small 3-5,000 BTU/hr system just to keep one cabin cool at night might work with that efficiency. It would need a big battery bank, probably 400 AH and a big solar array, about 600 watts to make it work.
Unfortunately, once you decide to use an AC at anchor, a generator is a requirement. You can offset daily running time of a 6 kWt generator by about 30 minutes by having a 600 Wt solar panel array.
Without a generator and only for nighttime use of a smallest highly efficient AC unit, such as the subject one, plus other typical on board appliances, one would need about 2 kWt solar array and ideally about 20 kWt*h battery bank for efficient charging. (20 kWt*h = 17 group 31 batteries, by the way.)