This study addresses the challenge of designing cost-effective and energy-efficient solar energy systems for large-scale, multi-functional building complexes, which typically exhibit high and diverse energy demands. Although integrating solar power with energy storage has shown promise, existing research rarely considers the full complexity of such building types or the trade-offs between cost and renewable energy use. To fill this gap, this study develops a novel assessment framework that quantitatively evaluates system performance across both energy and economic dimensions. The framework is applied to a real-world airport cargo terminal comprising ten functional zones, evaluating six system configurations with different photovoltaic areas and battery capacities. Two optimization objectives are considered: maximizing the share of energy supplied by solar generation and minimizing the levelized cost of electricity. The results show that two of the six configurations stand out as most representative: Case 3 adopts full rooftop and façade photovoltaics with an 87.94 MWh battery, enabling 60 % renewable energy penetration and the highest overall performance score of 4.6 (out of 6), though it requires 14.5 % higher investment; Case 5 uses only façade photovoltaics without storage, delivering the maximum cost saving of 10.4 % and the lowest energy cost of 0.49 CNY/kWh. The findings reveal a clear trade-off between maximizing renewable energy use and minimizing cost. This work contributes a novel, scalable framework for evaluating and optimizing solar energy systems in complex building environments, offering practical decision support for designers, policymakers, and investors seeking to promote sustainable urban energy transitions.