The water-intake temperature is a key factor affecting the system energy efficiency of an open-loop surface water source heat pump system (SWHPS). In addition to the conventional single-pipe water-intake design, we proposed two new design options that can improve SWHP efficiency. The numerical model that pertains to a SWHPS is presented and parameters such as the fluid-intake temperature and energy-saving rate of the heat pump system are analyzed and compared with experimental measurements. Our results demonstrate that on the basis of energy-saving rate, reducing the velocity of the water delivery has no significant influence while intake via multiple ports delivers superior efficiency. In conclusion, the water-intake design impacts on the SWHPS energy-saving rate because of its efficiency in drawing lower temperature water from a water retention body during summer. The method presented in this paper can provide a reference for a more detailed improvement on the energy performance of an open-loop SWHPS. (C) 2012 Elsevier B.V. All rights reserved.