The 1800XTSx Wine Cooling Unit by CellarPro is rated for external use in environments that range from 40°F to 95°F and is designed for Wine Cellars up to 400 Cu. Ft. If you are installing this unit in an environment that gets down to 20°F, we suggest adding a Compressor Heater modification to your cooling unit. The Compressor Heater attaches to the compressor and provides reliable peak heating during critical cold periods. This Wine Cooling Unit provides Outstanding Performance, Adjustable Humidity Control, and Maximum Cooling Power. Cooling Unit is designed to be installed through an external wall and vents in the rear. Added to this cooling unit is an outdoor hood, a condensate drain line, coated condenser coils, and the option of a power cord modification.