I have been looking at engles at the boat show but had a friend give raving reviews of the coleman for its low power draw. My understanding is that in just cooling mode in 85 degree temps it will draw less than one amp.
at full freeze 0F in 104 degree temps it will draw about 4 amps. The engle type compressor turns on and off... the coleman runs continuously unless it gets below the target temp. Anyway... base line seems to be that you need to start at about 20 to 30 amps per day draw at 12 volts to keep the drinks cold and up to 100 amps per day to deepfreeze stuff to 0F.
however coleman no longer makes these. if your lucky you can call one of the coleman outlet stores and find one still on the shelves for 299.00 clearance. To buy the same model from the manufacture global cooling will cost 600 or 700 dollars.
I just ordered store display from an outlet in alabama for 250 +20 in shipping. It's the right price if you can find one and the right size for a small boat like I have.