Techno-economic optimization of PV-battery systems in five Australian states

This paper presents a comprehensive techno-economic optimization model to examine how optimal configurations of residential PV-battery systems have evolved across five Australian states over a twelve-year period (2013/14 to 2024/25), driven by changes in policy, electricity tariffs, and technology costs. As the global leader in rooftop solar adoption, Australia offers a valuable case for understanding the long-term dynamics of distributed energy systems. Unlike previous studies that focus on a single metric or static analysis, this research provides three key contributions: (a) a multi-indicator framework that evaluates financial and technical performance using metrics such as Net Present Value, Selfe-Consumption and Selfe-Sufficiency ratios, Cost of Electricity, and Curtailed-Supply Fraction; (b) a long-term temporal analysis that compares optimal system configurations and performance indicators across twelve consecutive years; and (c) a geographically diverse case study across Queensland, New South Wales, South Australia, Victoria, and Tasmania to capture regional variation. Results show that PV systems consistently delivered substantial financial benefits across most states, with average IRRs of ∼20 % and household electricity costs reduced by around 35 %. The highest savings were observed in Queensland, where PV-battery systems cut household electricity costs by up to 72 % in 2023. In the early years, optimal PV sizes ranged from 4 to 6 kW but expanded to 15–16 kW in recent years due to declining technology costs. Battery adoption, which became financially viable only from 2023 onward, increased household self-sufficiency to an average of 60 % and up to 76 % in South Australia, although self-consumption fell to 30–40 % in some oversized systems. Tasmania was an outlier, where PV adoption was not financially attractive until after 2015, and batteries remained non-viable throughout the study period. Highlights • PV systems consistently delivered strong economic returns across five Australian states over 12 years, except Tasmania during early years. • Average Internal Rate of Return (IRR) reached approximately 20 % in high-adoption states. • Household electricity costs reduced by an average of 35 %, with peak savings up to 72 % in Queensland (2023–24). • Optimal PV system sizes increased from 4 to 6 kW (2013–2018) to 15–16 kW in recent years, driven by declining PV prices and battery viability. • Battery integration became financially viable from 2023, increasing household energy self-sufficiency to as high as 76 %.