In environments where climate policy has partial coverage or unequal participation, carbon dioxide (CO2) emissions or economic activity may shift to locations and sectors where emissions are unregulated. This is referred to as leakage. Leakage can offset or augment emissions reductions associated with a policy, which has important environmental and economic implications. Although leakage has been studied at national levels, analysis of leakage for subnational policies is limited, despite greater market integration and many existing state and regional environmental regulations in the U.S. This study explores leakage potential, net emissions changes, and other social implications in the U.S. energy system with regionally differentiated pricing of power sector CO2 emissions. We undertake an economic analysis using the US-REGEN model, where power sector CO2 emissions are priced in individual U.S. regions with a range of social cost of carbon (SCC) values. Policy makers are considering SCC estimates for valuing potential societal damages from CO2 emissions. In this study, we evaluate the emissions implications within the SCC pricing region, within the power sector outside the SCC region, and outside the power sector (i.e., in the rest of the energy system), and estimate other potential societal effects, such as to electricity prices, power sector investments, and overall consumption. Our results indicate that CO2 leakage is possible within and outside the electric sector that would affect CO2 reduction benefits, ranging from negative 70% to over 80% in our scenarios, with primarily positive leakage outcomes. Electricity price changes and broader economic effects are also observed within and across regions. Constraining power imports into the SCC pricing region likely reduces leakage, but could also result in lower overall emissions reductions, as well as larger price increases. Leakage rates, net emissions outcomes, electricity price changes, fuel market effects, and macroeconomic costs vary by region of the country, time, policy stringency, policy design (e.g., leakage mitigation provisions), policy environment in neighboring regions, and price responsiveness of demand.