In the present research, a methodology is proposed to optimize the solar collector area and ground heat exchanger length for achieving higher COP of Solar Assisted Ground Source Heat Pump (SAGSHP) system using Taguchi method and utility concept. Four operating parameters for solar collector and four parameters for ground heat exchanger have been selected with mixed level variation using an L-18 (2(1), 3(7)) orthogonal array. The key parameters such as solar collector area, ground heat exchanger length and COP of the SAGSHP system are optimized to predict the best levels of operating parameters for maximum COP of SAGSHP system. Lower the better concept has been used for the solar collector area and ground heat exchanger length whereas higher the better concept has been employed for the COP of SAGSHP system and the results have been analyzed for the optimum conditions using signal-to-noise (SN) ratio and ANOVA method. Computations were carried out for 18 experimental trial runs by considering 2 ton heating load in winter season. The optimum COP for SAGSHP was estimated to be 4.23 from the utility concept, which is 8.74% higher than the optimum COP predicted by Taguchi optimization. Optimization of solar collector area and ground heat exchanger length by the utility concept has shown only about 2.3% reduction in area and 1.6% reduction in length respectively compared to those values optimized by the Taguchi method. (C) 2014 Elsevier B.V. All rights reserved.