The goal of the conducted research was to assess the economic profitability of investment in a photovoltaic power plant located in south-east Poland, taking into consideration the whole invested capital, regardless of its origin. To determine such profitability, the NPV (Net Present Value) was used as well as the DPBT (Dynamic [Discounted] Pay Back Time). Empirical data was obtained from Energia Dolina Zielawy Sp. z o.o., with its registered office in Wisznice, which owns a photo-voltaic farm with 1.4 MW power, located in Bordziłówka (commune of Rossosz, province of Lublin). In accordance with the adopted assumptions described in the methodology section, the net present value of the investment in both variants was above zero, thus being economically efficient. The discounted period of payback time DBPT for the version with a subsidy was 9 years, whereas the option without subsidy extended that period to 13 years, and in the case of not taking the PMSPE into account – 18 years, still significantly shorter than the assumed 25-year period of use.