Integration of renewable sources in buildings: A review of energy savings, feasibility, and challenges

With rising energy demands and intensifying commitments to cut greenhouse-gas emissions, integrating renewable energy into buildings has become a cornerstone of sustainable development. Yet, existing studies are fragmented across technologies, climates, and building types. This systematic review synthesizes 92 peer-reviewed articles, screened from an initial pool of 177, to identify patterns, challenges, and opportunities in building-integrated renewable energy. The central finding is the decisive trend toward hybrid system configurations, present in over 80 % of reviewed studies, which consistently outperform single-technology approaches in efficiency, resilience, and sustainability. Comparative analysis shows that optimal mixes are highly context-specific, varying by climate, building typology, and policy environment. The review also identifies persistent research gaps: inconsistent application of life-cycle assessment and techno-economic indicators, limited empirical data for commercial and high-rise buildings, and insufficient attention to policy mechanisms that drive adoption. By linking hybrid system performance to climate and building typologies, this review provides an integrative synthesis that moves beyond technology catalogues and establishes a clear thesis: hybrid, context-sensitive systems represent the most robust pathway for building decarbonization. Addressing these gaps will require methodological rigor in performance evaluation and stronger integration of policy and economic perspectives into technical research. The synthesis establishes a conceptual roadmap for advancing hybrid renewable systems in buildings and identifies research priorities to support the transition toward net-zero energy buildings.