Corsair 31 trimaran. We spend 5 months full time live aboards in FLA keys. For past 6 years we used ice. Took a Coleman extreme cooler and glued 3 extra inches of pink styro foam to bottom and sides, nothing on lid as no more room. We would go 8 days on two 10 p0und bags of ice when temps inside boat averaged 75 degrees. I put a drain outlet on it to let out the melted ice twice a day. That enabled me to measure how many ounces of ice melted. Ussually it was 3 pounds a day. But if it was 85 degrees then more like 4 pounds a day and never more than 5.
This winter I abandoned the ice and bought an el cheapo alpi cool. Cooler box. Compressor style cooler half the weight of an engel and only 250 bucks. Again I glued on pink foam to add insulation. So far after one month it's work ok on a 80 amp agm battery and two 100 watt solar panels. Battery is topped off by noon on sunny and partly sunny days. battery has stayed at least 12.6 volts no load come morning time. Drops to 12.4 volts under 3 amp frig load. Still don't know about cloudy days. Fingers crossed on the alpi cool. It's quiet , light and cheap. But the manual is Chinese so have no idea how to change settings yet other than temp. Will tell you a couple years from now if it's reliable