||The number of apartment houses is recently increasing and various heating methods are adopted for the indoor heating in the apartment house in Korea. Ondol which is the radiation floor heating system is the most popular heating system among the various methods. The users and engineers have a fixed idea about the construction and operation method of Ondol caused from an experience of use of the Goodle(a Korean traditional heating system). So many users and engineers use the Ondol system which has high heat capacity and heavy weight. Therefore many problems are occurred because of heavy weight of Ondol such as energy waste due to high heat capacity, increasing of construction cost and difficulty of remodeling and maintenance. This is a preliminary study for the development of the prefab Electric Ondol system using PTC thermistor function. The aims of this study are reducing energy waste due to excessive thermal storage of Ondol, the development of an Ondol system that is easy to maintain and to reduce the weight of Ondol structure. As the results, electric energy consumption per hour of electric ondol system was 1.32∼1.48kwh per hour, 1.62∼1.77kwh per hour in traditional ondol system. Total electric energy consumption for 6 hours was 8.34kw in electric ondol system and 10.21kw in in traditional ondol system. After all, 18.4% of energy saving could be achieved. This result was caused by PTC thermistor function.