Thermoelectric cooling technology operates on the principle of the so-called Peltier effect. In this effect, electric current passes through a special element composed of two different materials, causing one side of the element to cool down and the other to heat up. In car coolers, the cold side is placed inside the box and extracts heat from the stored food and beverages. The heat is then dissipated from the hot outer side into the surroundings, most often with the help of a small fan. The system does not contain a compressor or refrigerants, making it lightweight, quiet, and shock-resistant. The cooling performance is dependent on the ambient temperature, usually capable of lowering the internal temperature by 15 to 20 °C below the ambient temperature. By reversing the polarity of the current, the function can be inverted, and the interior space can be heated instead.