Problems in the operating and calculation of payback of photovoltaic systems in buildings

The objects of the research are the solar photovoltaic systems (PV) that generate a significant amount of the electrical consumption in the building. This paper describes the parameters that affect the payback period of photovoltaic systems. Analysis of the first year of use of specific photovoltaic system (Building of a warehouse in Pärnu) is presented. The paper contains a analysis of the actual payback of photovoltaic systems under different scenarios of changes in electrical tariffs in the future. If calculating based on positive scenario (significant increase of tariffs) return of investment for specific PV in Pärnu is 9,5 years. If the increase in tariffs is minimal (negative scenario), the return of investment will two years later.