In Poland, the development of photovoltaic (PV) installations is an important element in the development of the Renewable Energy Sources (RES) sector and supports the prosumer power industry. The purpose of the article is to present a case study of the PROSUMENT program. It analyzes the data available to date on the development of the PV market in Poland. Apart from the costs of installing the PV systems, the article analyzes the profitability of investment for different micro-power installation capacities. A calculation for micro-power installations subsidized under the PROSUMENT program for various PV capacities is presented, along with the actual amount of the subsidy. The adopted calculation methodology is a comparative verification analysis of the investment cost estimate for a for the two studied PV facilities, i.e., Micro-power installation 1 and Micro-power installation 2. The building’s annual energy demand was adopted at the same level for both examples, with fixed active energy and distribution fees. The study includes a cost estimate for installing the PV systems and the profitability of the investments for various micro-power installation capacities. The analysis of the subsidy under the PROSUMENT program demonstrated that, in the analyzed period of 2016−2020, the best results were achieved by investments with a capacity of 10 kWp. In terms of the net subsidy value, the best results ranged between 27.20 and 19.10% of the total investment costs. Development of the Polish prosumer power market requires building public awareness of prosumer power production as an opportunity for the growth of the Polish economy.