<p>The growing worldwide demand for energy underscores the critical shift required toward sustainable systems. Solar power stands out among renewables as a dependable and abundant resource capable of curbing greenhouse gas emissions and strengthening energy security. Situated within the planet’s sunbelt, Iran exhibits considerable solar potential across its varied climates. This research introduces an integrated assessment framework, merging GIS-based solar mapping, PV system simulation via Pvsol, and the TOPSIS multi-criteria method to prioritize solar deployment on essential public infrastructure. The approach was tested at four hospitals in distinct Iranian climatic zones: temperate (Mazandaran), cold (Ardabil), hot and dry (Yazd), and hot and humid (Hormozgan). Following GIS suitability analysis, detailed system designs were simulated in Pvsol and then evaluated using TOPSIS according to energy output, capacity, performance ratio, and carbon reduction. Collectively, the proposed installations provide 2.2 MW of capacity, yielding roughly 4.67 GWh yearly and averting over 2.16 million kg of annual CO₂ emissions. Despite lower irradiance, the Ardabil site ranked highest overall due to an 89% performance ratio. The remaining hospitals achieved solar energy shares of 47% (Hormozgan), 43% (Yazd), and 29% (Mazandaran). These outcomes indicate that prioritization should extend beyond solar radiation to include integrated techno-environmental factors. The GIS–Pvsol–TOPSIS model thus offers a replicable tool for guiding sustainable energy investment in healthcare and other public infrastructure globally.</p> Graphical abstract <p></p>