378-26

Optimal Sizing of Photovoltaic System and Battery Storage in Self-Consumption Applications under Contemporary Regulatory Conditions

S. Seme(1,2), J. Počivalnik(1), D. Kuhar(1), B. Stergar(1), E. Simonič(1), K. Sredenšek(1,2)

1. Faculty of Energy Technology, University of Maribor, Krško, Slovenia

2. Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia

2026-06-27

Photovoltaic systems integrated with battery storage are increasingly implemented within self-consumption schemes. Nevertheless, system sizing is frequently based on installed capacity limits rather than on a comprehensive techno-economic assessment of long-term performance. This paper investigates the optimal sizing of photovoltaic and battery storage systems for a small industrial consumer operating under current regulatory conditions in Slovenia, where battery storage integration is mandatory due to low-voltage network constraints. Several combinations of photovoltaic system power and battery storage system capacity are evaluated using key economic indicators, including payback period and cumulative profit over a twenty-year operating period. Investment costs are derived from representative market-based component prices, and the national self-consumption billing framework is incorporated into the assessment. The results show that increasing battery storage capacity improves long-term profitability for small photovoltaic installations, while for larger systems, higher storage capacities reduce cumulative profit due to increased investment costs. The findings confirm that minimizing payback period does not necessarily correspond to maximizing long-term profit and emphasize the importance of balanced system sizing.

Key words: photovoltaic system, battery storage system, payback period, optimal sizing, electrical energy production

[1] I. E. A. P. P. S. Programme, Active Power Management of Photovoltaic Systems - State of the Art and Technical Solutions, 2024.

[2] A. Pena-Bello, R. Junod, C. Ballif, and N. Wyrsch, “Balancing DSO interests and PV system economics with alternative tariffs,” Energy Policy, vol. 183, Dec, 2023.

[3] A. Kesküla, K. Grjaznov, T. Sepp, and A. Allik, “Optimal Sizing of Residential PV and Battery Systems Under Grid Export Constraints: An Estonian Case Study,” Energies, vol. 18, no. 16, Aug 19, 2025.

[4] H. K. Ren, M. McCulloch, and D. Wallom, “Optimal sizing of solar photovoltaic and lithium battery storage to reduce grid electricity reliance in buildings,” Conference of ECEEE 2022 Summer Study on energy efficiency, 2023.

[5] R. Nematirad, A. Pahwa, B. Natarajan, and H. Wu, “Optimal sizing of photovoltaic-battery system for peak demand reduction using statistical models,” Frontiers in Energy Research, vol. 11, Dec 7, 2023.

[6] A. Gonçalves, G. Cavalcanti, M. Feitosa, R. Dias, A. Pereira, E. Jatobá, J. de Melo, M. Marinho, A. Converti, and L. Gómez-Malagón, “Optimal Sizing of a Photovoltaic/Battery Energy Storage System to Supply Electric Substation Auxiliary Systems under Contingency,” Energies, vol. 16, no. 13, Jul, 2023.

[7] P. N. D. Premadasa, C. M. M. R. S. Silva, D. P. Chandima, and J. P. Karunadasa, “Optimal Sizing of Solar Photovoltaics and Battery Storage for Domestic Prosumers Using Genetic Algorithm,” Moratuwa Engineering Research Conference (MERCon), 2023.

[8] T. Iwayemi, “PV/Battery System Sizing,” International Journal of Scientific Research and Modern Technology, vol. 3, pp. 101–122, 06/28, 2024.

[9] C. Rus-Casas, C. Gilabert-Torres, and J. Fernández-Carrasco, “Optimizing Energy Management and Sizing of Photovoltaic Batteries for a Household in Granada, Spain: A Novel Approach Considering Time Resolution,” Batteries-Basel, vol. 10, no. 10, Oct, 2024.

[10] B. Li, M. Li, S. Yan, Y. Zhang, B. Shi, and J. Ye, “An optimal energy storage system sizing determination for improving the utilization and forecasting accuracy of photovoltaic (PV) power stations,” Frontiers in Energy Research, vol. 10, Jan 18, 2023.

[11] Act on the Methodology for Charging Network Fees for Electricity Operators (Official Gazette of the Republic of Slovenia, No. 146/2022), 2022.

[12] K. Sredensek, J. Pocivalnik, D. Kuhar, E. Simonic, and S. Seme, “Transformation of the Network Tariff Model in Slovenia: Impact on Prosumers and Other Network Users,” Energies, vol. 19, no. 2, Jan 22, 2026.

[13] M. Aghaei, A. Fairbrother, A. Gok, S. Ahmad, S. Kazim, K. Lobato, G. Oreski, A. Reinders, J. Schmitz, M. Theelen, P. Yilmaz, and J. Kettle, “Review of degradation and failure phenomena in photovoltaic modules,” Renewable & Sustainable Energy Reviews, vol. 159, May, 2022.

[14] J. Ko, K. Kim, J. Sohn, H. Jang, H. Lee, D. Kim, and Y. Kang, “Review on Separation Processes of End-of-Life Silicon Photovoltaic Modules,” Energies, vol. 16, no. 11, May 25, 2023.

[15] N. Collath, B. Tepe, S. Englberger, A. Jossen, and H. Hesse, “Aging aware operation of lithium-ion battery energy storage systems: A review,” Journal of Energy Storage, vol. 55, Nov 25, 2022.

[16] Climate and Energy (Slovenia), Contribution for Energy Efficiency, Energetika Portal, 2025.