In recent years, photovoltaics gained a very large space in the international arena and have become the world s third largest source of renewable energy, second only to hydropower and wind energy. In Brazil, despite all the favorable natural features in terms of solar availability and production of high quality silicon s possibilities, photovoltaics has an incipient participation in the energy matrix. The Agency National of Electric Energy (ANEEL), through the Resolution 482, sought to establish the general conditions and reduce existing regulatory barriers aimed at the expansion of this type of generation through the introduction of electric power compensation system (net metering). This study investigates the best time to invest in a project to establish a grid-connected photovoltaic system, from the perspective of the investor, applying the Theory of Real Options (TOR). The analysis was based on estimated cash flow throughout the life of the generating system and the project value was calculated considering that the investor could deploy it immediately or have the option of waiting for a more appropriate time. Traditional methods of investment appraisal as the Net Present Value (NPV), Internal Rate of Return (IRR) and payback were used and real option theory (TOR) as well. From the analysis done in this study, it was concluded that, given the specific conditions of the proposed project, the best option would be held immediately the grid-connected photovoltaic system.