the investment yields a negative NPV and that the payback period is long (between 8.3 and 10.2 years). Kahn and Iqbal [58] consider potential remedies to the problems of stand-alone decentralised energy systems which sometimes make them nonviable options – such as low capacity factors and excess battery costs. The authors suggest that stand-alone systems could be used as a hybrid with other sources of energy carrier (both renewable and non-renewable) so as to increase their cost effectiveness. They use HOMER software to find the optimal combination of energy technologies in Newfoundland. The results suggest that some hybrid systems (such as a wind–diesel–battery hybrid system) are commercially feasible, but that other systems (such as an environmental friendly hydrogen-based hybrid system) are too costly to be commercially viable