A cooling dominated Hybrid Ground Source Heat Pump System (HGSHPS) is utilized to cover the energy demands of an office building. The energy demands are computed by TRNSYS 16.1, considering two different scenarios, based on different glazing properties. A ground loop consisted of a rectangular field of 15 borehole heat exchangers is utilized to cover building loads. GLD 2009 sizing software calculates borehole length setting two different fixed temperatures for the heat carrier fluid entering heat pump, 30 degrees C and 33 degrees C. Assuming different cooling tower capacity, the desired flow rate is estimated for a cooling range of 5.7 degrees C (the difference between the water inlet and outlet temperature). A MATLAB code is created to calculate the required pressure drop per packing height of cooling tower for four packings in different operating conditions. (c) 2012 Elsevier Ltd. All rights reserved.