Benefit Mechanism and Enhancement Strategy of High‐Proportion Building Photovoltaic Systems Under Carbon Reduction Constraints

Photovoltaics (PV) are a key pathway towards carbon neutrality in the building sector. However, under high‐proportion PV applications, intensified source–load mismatch and declining export value cause divergence between overall system benefits and PV utilisation benefits, whereas the related mechanisms remain unclear. This study establishes a benefit evaluation framework considering carbon reduction constraints, equivalent grid absorption costs and multi‐stakeholder benefit differences, revealing the contradiction between ‘overall benefit optimisation’ and ‘PV utilisation optimisation’. Based on a retrofit office building in Beijing, three technology‐oriented pathways, including thermal performance enhancement (I), heating and cooling electrification (II) and sole PV capacity expansion (III), were comparatively analyzed under a unified zero‐carbon constraint. Results show that the system comprehensive benefit rate follows III > I > II (13.3%/12.2%/10.4%), indicating that PV provides more direct economic returns than demand‐side energy‐saving measures under the current pricing mechanism. In contrast, the PV utilisation benefit rate follows II > I > III (16.8%/13.7%/13.3%), demonstrating that stronger source–load coordination improves the economic value of PV electricity. Further analysis indicates that benefit enhancement depends on the dual‐driven mechanism of ‘effective generation–effective utilisation’. Finally, a zero‐carbon building demonstration project was implemented, providing support for the benefit evaluation and optimisation of high‐proportion building PV systems.