Installations of solar photovoltaic systems are growing as a promising renewable alternative to generate electricity. This paper aims to compare the power generation potential of a photovoltaic solar plant installed in a Vale do Paranhana-Brazil company with the power supplied by the utility. By demonstrating the composition of the electricity tariff currently used by the company, it was possible to perform a subsequent calculation of return on investments. The plant sizing calculation possibly did not take into account the company's consumption data. This factor influences the financial performance expected by investors.