Many US states rely on energy efficiency goals as a strategy to reduce CO 2 e emissions and air pollution, to minimize investments in new power plants, and to create jobs. For those energy efficiency interventions that are cost-effective, i.e., saving money and reducing energy, consumers may increase their use of energy services, or re-spend cost savings on other carbonand energy-intensive goods and services. In this paper, we simulate the magnitude of these 'rebound effects' in each of the 50 states in terms of CO 2 e emissions, focusing on residential electric end-uses under plausible assumptions. We find that a 10% reduction in annual electricity use by a household results in an emissions' reduction penalty ranging from 0.1 ton CO 2 e in California to 0.3 ton CO 2 e in Alabama (from potential emissions reductions of 0.3 ton CO 2 e and 1.6 ton CO 2 e, respectively, in the no rebound case). Rebound effects, percentage-wise, range from 6% in West Virginia (which has a high-carbon electricity and low electricity prices), to as high as 40% in California (which has low-carbon electricity and high electricity prices). The magnitude of rebound effects percentage-wise depends on the carbon intensity of the grid: in states with low emissions factors and higher electricity prices, such as California, the rebound effects are much larger percentage-wise than in states like Pennsylvania. Conversely, the states with larger per cent rebound effects are the ones where the implications in terms of absolute emissions changes are the smallest.