Reducing U.S. Residential Energy Use and CO₂ Emissions: How Much, How Soon, and at What Cost?

There is growing interest in reducing energy use and emissions of carbon dioxide from the residential sector by deploying cost-effectiveness energy efficiency measures. However, there is still large uncertainty about the magnitude of the reductions that could be achieved by pursuing different energy efficiency measures across the nation. Using detailed estimates of the current inventory and performance of major appliances in U.S. homes, we model the cost, energy, and CO₂ emissions reduction if they were replaced with alternatives that consume less energy or emit less CO₂. We explore trade-offs between reducing CO₂, reducing primary or final energy, or electricity consumption. We explore switching between electricity and direct fuel use, and among fuels. The trade-offs between different energy efficiency policy goals, as well as the environmental metrics used, are important but have been largely unexplored by previous energy modelers and policy-makers. We find that overnight replacement of the full stock of major residential appliances sets an upper bound of just over 710 × 10⁶ tonnes/year of CO₂ or a 56% reduction from baseline residential emissions. However, a policy designed instead to minimize primary energy consumption instead of CO₂ emissions will achieve a 48% reduction in annual carbon dioxide emissions from the nine largest energy consuming residential end-uses. Thus, we explore the uncertainty regarding the main assumptions and different policy goals in a detailed sensitivity analysis