Harnessing the flexibility of power-to-heat operation in building and district heating to support electricity systems: A review

This review focuses on the literature concerning the flexible operation of power-to-heat (P2H) systems, particularly heat pumps, which are used to support the electricity system. It examines how thermal storage and the thermal inertia of buildings enable P2H technologies to act as flexibility resources in both district heating and distributed heating contexts. A systematic literature selection process is employed to analyse topic coverage and applied methods across the existing research. The review surveys modelling and simulation approaches, tools and control strategies for P2H flexibility. It also examines relevant regulatory and market frameworks and identifies lessons from advanced case studies and operational systems. The review concludes by identifying methodological gaps and priority research areas for realising the potential of P2H as a major contributor to system flexibility in low-carbon energy systems. We find that, while many studies have demonstrated flexibility potential of P2H assets in small-scale or simulation-based settings, significant gaps remain in terms of scalable and deployable control strategies, large-scale field validation, and the consideration of cross-sectoral synergies in system design and planning.