The single most important fact about marine refrigeration is that it will enhance your time on board through the convenience of cold drinks and fresh food. However, the amount of time required to provide this luxury is not to be overlooked. If you spend a lot of time at the dock where shore power is readily available, if you have an onboard generator that you use frequently, or if you live aboard, your best choice is a 110vAC unit. They're relatively inexpensive, dependable, easy to install, and should give you years of trouble-free service.

Most boaters don't live at the dock and use 12vDC units to provide the same dependable refrigeration as they have in their homes. The simple installation of only two major components—compressor and evaporator—make these units very popular. The compressor cycles on and off as the box warms and cools - 30 minutes running time out of every hour is the norm. While these units draw little current when running, the total amperage draw over a 24-hour period can be more than the boat's electrical system is prepared to handle. A close evaluation of your boat's battery size and recharge capability is in order when installing a 12vDC refrigeration system.

Most 12vDC units come with an air-cooled condenser, although a water-cooled condenser is preferable, especially in warmer climates. Water cooling is more efficient, so you get greater cooling capacity with a smaller unit, and they can be installed almost anywhere. Air-cooled condensers must be mounted where they can be ventilated to dissipate the high heat removed from the ice box.

For 12vDC running at dockside, simply plug in your battery charger and replace the battery power you're using. But away from the dock, your primary consideration is how often and how long you must run your engine to have ice and cold food. Having a dedicated battery bank for your refrigeration unit is a good idea, but remember that you still have to run your engine to replace the battery drain.

You can increase your options with an AC/DC icemaker. The dual-voltage units switch from AC to DC automatically when the AC power source is shut off.

Thermoelectric refrigeration is also 12vDC, but uses no refrigerant and has no moving parts except a heat-dissipating fan. These quiet units can last a lifetime, and installation is simple. But they're not for every boat. They're less efficient than other types, requiring about 100 amps daily to cool a 2-cu. ft. box. They will cool the box to 40-50° below ambient temperature, which is inadequate for the tropics and possibly not worth the power drain. Small portable units use only half the power of full-size units. They're a smaller, lighter, and convenient alternative to hauling that heavy, bulky cooler of ice on every outing.

If you plan to convert your existing ice box to a refrigerator and/or freezer unit using a conversion kit, it is absolutely critical that you pay special attention to the box's insulation. Heat loss through leakage can be cut in half by increasing the insulation from two to six inches.

Engine-driven systems with holding plates are the most powerful system for those wanting deep freezes and lots of ice. The compressor runs only once or twice a day, for short periods of time. However, the initial cost is double or triple the cost of a 12vDC unit, and is more complicated so there's a greater potential for problems.

Look for marine-grade construction materials. Most holding plates are made of stainless steel; electropolished stainless steel is more corrosion-resistant and more attractive. Water-cooled condensers exposed to seawater should be made of a noncorrosive material such as cupronickel. Marine-grade materials add to the initial cost of the unit, but if you're going to make this kind of investment, buy a dependable unit that will last. Check the manufacturer's warranty - longer is better.