Transitioning to low carbon tourism demands that heritage places balance decarbonization with conservation responsibilities, visitor experiences, institutional coordination and rising demand. This study focuses on green energy transition in UNESCO World Heritage tourism in Tamil Nadu with the integrated Governance – Retrofit – Demand (GRD) framework. The framework explores retrofit feasibility, institutional governance and demand-side behaviour as factors influencing visitor support and considers awareness as a direct and moderating factor. A descriptive analysis, reliability test, correlation, regression, site comparison and PLS SEM are applied using a respondent level data set of 330 respondents in Mahabalipuram, Great Living Chola Temples, Nilgiri Mountain Railway and Western Ghats. Constructs had high internal consistency from 0.914 to 0.930 (Cronbach, 1951). Overall support was significantly predicted by retrofit feasibility (β = 0.355, p < 0.001), institutional governance (β = 0.293, p < 0.001), and demand-side behaviour (β = 0.318, p < 0.001), explaining 47.8% of the variance. PLS-SEM further confirmed significant effects of RF→OS (β = 0.251, p < 0.001), IG→OS (β = 0.285, p < 0.001), and DB→OS (β = 0.321, p < 0.001). Awareness had no significant direct effect (β = 0.069, p = 0.086) but did significantly moderate the relationship between RF and OS (β = 0.157, p = 0.002). The results indicate that the integrated heritage-energy governance approach is required in Tamil Nadu, encompassing technical retrofitting, institutional coordination, demand management and effective visitor communication