The U.S. Environmental Protection Agency finalized emissions limits for new and existing fossil fuel-fired power plants under Sections 111(b) and 111(d) of the Clean Air Act in May 2024. The complex incentive structure of the rules along with key market, technology, policy, and other uncertainties suggest that several alternate technology strategies may offer approaches for compliance. This analysis uses EPRI’s U.S. Regional Economy, Greenhouse Gas, and Energy Model (US-REGEN) model to evaluate U.S. power sector impacts under EPA’s finalized 111 rules, while exploring a range of sensitivities that include higher natural gas prices, possible future compliance for existing natural gas power plants, changing technology costs, higher electricity demand, and policy landscape uncertainty including deep decarbonization targets for the electric sector. Model results suggest that future rules for existing gas plants may have the potential to accelerate emissions reductions, although these impacts may be more limited at higher gas prices. While impacts on coal capacity with and without carbon capture remain consistent across the scenarios analyzed, the deployment of gas with carbon capture is limited except in scenarios with low costs or near-term deep decarbonization targets.