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This research analyzed and compared economic feasibility of installation options of solar rooftop systems between being system owner and private power purchase agreement (Private PPA) by using Thammasat University, Rangsit Centre as a case study. The indicators used were levelized cost of electricity (LCOE) and net present value (NPV). In addition, the risk assessment of the project was performed by sensitivity analysis and scenario analysis considering the variables (1) system cost (2) the rate of increase in the electricity tariff and (3) the amount of electricity that can be produced from the solar rooftop. The results showed that under the base case assumption, the system owner option was more cost effective with lower LCOE and higher NPV than Private PPA option. The sensitivity analysis and scenario analysis results showed that the system owner option tended to be more attractive than the private PPA option under the situations of low system costs and high escalation rates of electricity tariff. On the other hand, under situations of high system costs and low escalation rates of electricity tariff, the private PPA will likely be more attractive than the system owner option. Moreover, if the amount of electricity produced from the solar rooftop reduces, the chance that the private PPA option will be more attractive. In addition, while the system owner option may have negative NPV in some situation, the advantage of the private PPA option is that the NPV will always be positive since there is no investment and expenses. The results of this study will be useful for decision makers to select the suitable installation option for themselves.
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