Two different options for the autonomous power supply of rural or/and remote buildings are examined in this study. The first one involves a PV - diesel based power system, while the second one integrates RES and hydrogen technologies for the development of a self - sustained power system. The main objective is the replacement of the diesel generator and a comparison between these two options for autonomous power supply. Model simulations of the two power systems before and after the replacement, an optimization of the component sizes and a techno - economic analysis have been performed for the purpose of this study. A sensitivity analysis taking into account future cost scenarios for hydrogen technologies is also presented. The results clearly show that the Cost of Energy Produced (COE) from the PV - hydrogen technologies power system is extremely higher than the PV - diesel power system. However, the adopted PV - hydrogen technologies power system reduces to zero the Green - House Gas (GHG) emissions. Moreover, the sensitivity analysis indicates that COE for the latter system can be further reduced by approximately 50% compared to its initial value. This could be achieved by reducing critical COE's parameters, such as PEM electrolyser and fuel cell capital costs. Hence, a possible reduction on the capital costs of hydrogen energy equipment in combination with emissions reduction mentioned above could make hydrogen - based power systems more competitive. (c) 2010 Elsevier Ltd. All rights reserved.