The research concerning ocean energy exploitation in North China is undoubtedly of significant importance to the development of the national ocean energy. The use of seawater heat pump (SWHP) systems is a better choice than air-source heat pump (ASHP) systems. The latter systems have a lower efficiency because of the formation of frost on the surface of its airside heat exchanger when the ambient air temperature is low. This paper reports research investigating the system efficiency of SWHP systems in areas of severe cold during winter. Experiments are conducted to compare the thermal performance of the beach well infiltration intake systems (BWIS) and the helical coil heat exchanger (HCHE) for SWHP systems in the Bohai Sea, Tianjin, North China. Heat transfer rate, COP (coefficient of performance) values, exergy efficiencies and exergy destruction rates of the SWHP systems with BWIS and HCHE are presented and compared with the ASHP systems. The study results indicate that the BWIS for SWHP systems has the highest thermal performance during the whole heating season in areas of severe cold during winter. That performance is observed because icing on the outer surfaces of the tubes of the HCHE and frost formation on the surface of the heat exchanger of the ASHP have great effects on the heat transfer performance. The Heating seasonal performance factor (HSPF) is used to express the performance of heat pump systems over the entire heating season. Economic analyses of the BWIS and HCHE are performed according to local economics to compare the application of the HCHE and BWIS, and the results indicate that the HCHE has a better economic value. (C) 2014 Published by Elsevier Ltd.