We performed a comparative study of electrical and thermal properties of ZnO- and SnO2-based varistor. The electrical properties of commercial ZnO-based varistor are equivalent to that found in SnO2-based varistor system. In spite of this, the SnO2 showed a thermal conductivity higher than commercial samples of ZnO-based varistor, which allied with its simpler microstructure and lower dopant concentration is a remarkable result that point out to the use of this system to compete commercially with ZnO-based varistor devices.