Abstract
The abandonment of conventional sources in favor of energy from renewable energy sources (RES) has a global dimension, and the dynamic increase in the share of energy from photovoltaic systems in the energy mix of many countries results from the possibility of obtaining it both on a small scale (micro-installations) and as part of economic investments (photovoltaic power plants). The study aimed to assess the economic efficiency of 22 photovoltaic farms located in northeastern Poland. The research covered 5 solar power plants with a capacity of up to 799 kWp (I), 13 between 800 and 1100 kWp (II), and 4 installations of 1.98 MWp (III). The evaluation was based on net present value (NPV), internal rate of return (IRR), payback period (PP), profitability index (PI), accounting rate of return (ARR). Additionally, a sensitivity analysis was carried out regarding the value of economic indicators. The analysis shows that all studied PV farms are economically justified investments (NPV > 0) regardless of the adopted scenario. Solar power plants of the largest analyzed capacity (group III) resulted in being the most profitable ones, but no linear relationship between the level of productivity and profitability was established. Due to the large variation in terrain shape in northeastern Poland, landscape value and social benefits, which are difficult to assess, the support system for investments regarding the construction of photovoltaic power plants proved to be the most effective in group I.