Perusal of my bill, OTOH, reveals that I am paying a (ludicrous) set fee for power, water, and garbage. Metered use only kicks in if I exceed the quota. Which I don't, even with a heater plugged in all winter. The message is clear: I need to consume more! Cold drinks and air conditioning, coming up!
I have some used Adler-Barbour cold machine parts sitting on the work bench that I have been meaning to install for a couple of years. The hold-up is that they have different-sized quick-disconnect fittings on them! I'm assuming that I'll be able to put them together using my automotive AC tools and Mad Science skilz. It turns out that those fittings are so expensive and/or unobtainable that it would have been cheaper and faster to shop around for other units that already had the right sized fittings and throw these away. But my blindered-mule phase was kicking in.
Adequate ventilation in the sail locker is a concern - may have to add some.
Some battery management devices (e.g. Victron stuff IIRC) has a feature to cut off the output if system voltage gets too low, preventing the fridge from killing your batteries.
Like Christian, I prefer to maintain cold drinks on board all the time. In the marina, the boat is my Man Cave. And it's my radio shack. And my paddling base. And my bicycling destination. And my downtown condo. At the factory state of insulation, I need to add ice two or three times a week, depending on the weather.
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Speaking of Mad Science, here's something completely different.
https://www.youtube.com/watch?v=twW36wFmm9U https://www.youtube.com/watch?v=R7YrCtDGI-E
These guys installed a product called a "keco cooler" which I see is no longer available but... It combined a Peltier cooler (which everyone knows is inadequate on its own for real chilled drinks in the summer) with a raw water heat exchanger. It was really over-priced, but people who tried them say that they worked. Although they didn't make ice. At least not on purpose.
Here's the thing - all the components of that cooler can be had cheaply from imported parts listed on Amazon and Ebay. The grand total is probably less than $100. Even if your Mad Science is a little rusty, there are plenty of step-by-step instructions on-line from people who use similar devices in brewing or other applications. The only tricky bit is keeping everything on 12VDC. The total power draw won't be any less than a traditional compressor system, but it looks like a fun and inexpensive project. That
might end up with useful refrigeration. One that I invested a couple of hours researching one weekend, but didn't take any farther. Yet. I'm guessing that the weak link would be keeping the raw water circulation going day and night.