Achieving Great Britain’s 2050 net-zero target requires coordinated integration of electricity, gas, and hydrogen systems. This paper presents a game-theoretic optimisation framework that evaluates competitive and cooperative investment and operational strategies within a bi-level structure combining long-term planning and short-term operational constraints. The competitive scenario is modelled through a Nash–Cournot equilibrium, while the cooperative scenario applies the Shapley value to ensure a fair allocation of costs and benefits among technologies.

Results show that both approaches enable decarbonisation, but cooperation delivers superior economic efficiency at the 2050 peak demand, achieving a 57% reduction in operational costs and complete decarbonisation, compared to residual emissions of 8161 tonnes under competition. Competitive strategies favour flexibility technologies such as Power-to-Gas (P2G) (11.7%) and Battery Energy Storage (BESS) (11.4%), whereas cooperative planning utilises lower flexibility (P2G 3.4%, BESS 4.5%) and greater nuclear baseload (20%–26%). Shapley value analysis quantifies each technology’s marginal contribution, identifying hydrogen technologies as major value drivers, while gas-to-hydrogen reforming with carbon capture and storage (G2G-CCS), biomass, and combined heat and power (CHP) require policy support. When market conditions are not favourable, electricity technologies require between £0.82 and 2.16 million in financial support.

The paper findings offer quantitative insights to guide policy development that incentivises collaboration and coordinated planning, supporting a resilient, fair, and economically efficient pathway to a net-zero energy system for Great Britain.