Almost all keg refrigerators are designed for indoor use only. For the most efficient operation, refrigerators should be located in a cool place out of direct sunlight, away from heating ducts or registers, and away from heat producing appliances such as a range, oven or dishwasher.
Keep in mind that the warmer the surrounding ambient temperature, the harder the refrigeration compressor will work to maintain the 36-38° F internal temperature which is critical for most ale and lager type beers. Also, the surrounding temperature should never exceed 110° F (43° C) or drop below 10° F (-12° C).
Keg refrigerators not specifically designed for outdoor use will not perform well in the warmer outside temperatures. The compressor will be stressed working to maintain the 36-38° F internal temperature, this will lead to the compressor overheating and eventually burning out.
There are a few models of keg refrigerator that are specifically designed for outdoor use. However, these units are usually quite expensive because they are typically designed with a heavy duty compressor unit and higher rated insulation in order to withstand the warmer outdoor temperatures.
If you intend to use a keg refrigerator outdoors, be sure to purchase a unit specifically designed for outdoor use.