We numerically analyzed the effect of the placement of a top discharge outdoor unit installed near a wall on the heat pump performance. The design parameters considered in this study were the height of the wall close to the outdoor unit and the distance between the wall and the unit. We then investigated the performance of the outdoor unit for various placements. Based on the results of the numerical experiments, the optimum placement of the outdoor unit near the wall was established. The optimum placement of the outdoor unit showed the ratio (COP/COPref) of 1.01, whereas the worst case resulted in 0.91. (C) 2012 Elsevier B.V. All rights reserved.