Operational Modeling and Performance Analysis of a Rooftop Photovoltaic System for Power Supply of Multi-Apartment Building Infrastructure

The increasing deployment of rooftop photovoltaic (PV) systems in multi-apartment buildings offers opportunities to improve energy resilience and reduce dependence on grid electricity, yet their real-world performance remains insufficiently documented. This study evaluates a rooftop PV system (32.3 kWp, 76 modules) with 92.16 kWh of lithium iron phosphate storage supplying the shared and critical infrastructure of a 16-story apartment building in Kyiv, Ukraine. Eleven months of metered operation, from October 2025 to August 2026, are compared month by month with a three-dimensional PV*SOL model of the same array. In the warm half of the year, the metered generation agrees with the simulation within −8.5%, which confirms the model inputs. From October to February, it falls to 43% of the simulated values, although measurements on clear days at the end of February show a peak output of about 15 kW, the same level as on clear summer days, so that the deviation is associated with the weather of the monitored season rather than with the configuration of the installation. Over the monitored period the plant generated 19.0 MWh, of which 34% was exported to the grid, and covered 38 to 48% of the 26.4 MWh demand of the monitored loads, compared with 27.5% obtained from a simulation without storage. The measured operation also documents a daily control strategy in which the battery is charged from the PV array during the day, discharged into the grid during the evening peak, and switched to a reserve mode with a minimum state of charge of 50 to 60% as soon as scheduled outages resume, which provides an explicit trade-off between revenue and resilience. The results show that the realized output of rooftop PV in such buildings is governed by the operating strategy and by the actual weather rather than by the rated capacity of the array alone.