The value of hot water system in Thailand, rarely mentioned or quantified, is almost 3,000 million Baht per year. The heat pump is an option of hot water system. The development of heat pump in Thailand is officially started in 2002 according to the program of subsidy for heat pump but before that there was some slow development. Comparing to the cost of hot water production from instantaneous system, local manufactured heat pump is commercial viable even without the subsidy. The imported heat pump compared to local production can be sold to only high end user or high awareness of energy. The important factor of heat pump development is depended on the selling price, performance, and the customer behavior. The highest efficiency may not be the winner in Thai market as the drivers for higher efficiency or co-efficiency of performance of heat pump is not so strong compared to the price. Some of information in this paper cannot be supported by the real data because of the brand name of heat pump cannot be published.