Can photovoltaic retrofit redefine heritage value? Practical and theoretical evidence from meta-analysis and multi-criteria evaluation of 133 international case studies over 35 years

This paper investigates the role of photovoltaic (PV) systems in accelerating the energy transition of built heritage through the comparative analysis of 133 international case studies realized between 1991 and 2026. Covering a wide range of climatic zones, regulatory frameworks, building functions, and heritage protection levels, the study adopts a mixed-method research framework that integrates archival analysis, policy review, technological assessment, quantitative energy evaluation, and critical architectural interpretation. The case studies enable the identification of performance patterns, temporal trends, and critical innovation thresholds, offering an evidence-based understanding of how aesthetic, technical, and energy performance goals negotiated in practice the trade-offs between decarbonization policies, technological feasibility, cultural values, product innovation, and social acceptance of PV adoption in historical environments. From a regulatory perspective, 47% of the analyzed buildings are formally listed, while others are subject to indirect heritage constraints, demonstrating that PV integration is not confined to weakly protected contexts. Case studies span from the 14th to the 20th century, and PV adoption is most frequent in residential, religious, office, and rural buildings, while cultural, educational, and institutional uses confirm the growing penetration of PV systems into public and highly symbolic building types. Crystalline silicon cells dominate due to reliability and availability, while glass-glass, frameless, and chromatically treated panels emerge after 2018 as enablers of higher architectural and energy integration. The PV fraction covering annual primary energy consumption ranges from approximately 10% to 149%, with a mean value of 60.7% and a median of 58.5%. More than 42% of the cases achieve coverage above 50%, while 21% reach full or surplus energy balance (≥100%). The temporal analysis identifies three evolutionary phases: experimental applications (1991-2001), visually subordinate and concealed solutions driven by conservative guidelines and early EU directives (2002-2017), and context-sensitive architectural integration (2018-2026) aligned with higher energy targets and technological maturation. Building on these findings, a data-driven design taxonomy was structured around emerging retrofit paradigms ( concealment, mimicry, transparency, and expression ) as guidance to inform future policy strategies, technological development, decision-making and design practices. This approach challenges and reinterprets the traditional principles of “ authenticity ” and “ reversibility ” from architectural conservation, adapting them to the language and design logic of PV retrofit. • Dataset of 133 international cases on photovoltaic retrofit of heritage buildings. • Cross-disciplinary framework balancing heritage, technological and energy measures. • Photovoltaic design taxonomy derived from real-world implementations.