Integrating demand flexibility into the planning and operation of residential PV–battery systems

Purpose This study examines how integrating demand-side flexibility into the planning stage of residential photovoltaic (PV)–battery systems influences optimal system sizing and operational performance. Design/methodology/approach A combined planning–operation optimisation framework is developed in which household electricity demand is decomposed into fixed and flexible components. The model simultaneously determines optimal PV capacity, battery size, and the scheduling of flexible loads. Twelve demand-flexibility scenarios are analysed based on different allowable load-shifting windows to evaluate how flexible demand affects system sizing and energy management. Findings Results show that incorporating flexibility systematically shifts demand toward solar generation periods, improving PV self-consumption and reducing reliance on battery storage. Battery capacity decreases by up to 33%, while PV capacity increases modestly by approximately 2.7%. Compared with a two-stage benchmark model, the proposed approach reduces total system cost by an average of 7%, with improvements reaching up to 9% at higher flexibility levels. Research limitations/implications The model assumes deterministic demand and PV generation over a 20-year horizon. Future research should incorporate stochastic modelling and extend the analysis to diverse climatic and socio-economic contexts. Social implications The results provide actionable insights for homeowners and energy planners by showing that incorporating demand flexibility can reduce storage requirements and improve investment efficiency. Originality/value Unlike conventional approaches that treat demand flexibility only at the operational stage, this study integrates flexibility directly into system planning. The findings demonstrate that co-optimising system sizing and demand scheduling yields more cost-efficient and technically effective PV–battery configurations.