The main drawbacks of using an extension cord with a refrigerator are the safety risk and reduced performance. The safety risk can be greatly reduced by using an appropriate cord -- never use a lightweight extension cord under 15 amperes or 1,825 watts. Even the best extension cord won't deliver 100 percent performance for your refrigerator, however. That reduced performance means the fridge has to work harder to maintain temperature, leading to increased energy consumption and higher electric bills.
Under no circumstances should you ever plug a refrigerator into an outlet or extension cord that is not grounded. You'll know when an outlet is grounded because it will have three holes instead of two. Because all 4.6-cubic foot refrigerators have three-pronged plugs, it's impossible to plug one into a two-hole outlet without removing the third prong. Do not remove the prong to force it, as it will cause a serious safety hazard, and do not adapt a two prong outlet into a grounded outlet with an extension cord, as these types of cords can't handle the voltage of a refrigerator.
Because a compact refrigerator is an indoor appliance, you may be tempted to use a typical indoor extension cord with it. In many cases, indoor extension cords are designed for use with low-voltage items such as lamps and phone chargers, and have as little as 7 amps. A refrigerator would need a heavy-duty cord, either a thick orange indoor/outdoor cord or a heavy 14- to 12-gauge cord designed to handle computer printers, air conditioners outdoor electronics.
The longer your extension cord, the more your compact refrigerator will have to work. Buy the shortest cord possible for your arrangement. Long outdoor cords designed for use with lawn care equipment are a better option than light- or medium-duty extension cords, but only for short-term temporary use. In addition to significantly reducing the effectiveness of the refrigerator, a long cord causes a safety hazard underfoot.