This Article, excerpted from Michael B. Gerrard & John C. Dernbach, eds., Legal Pathways to Deep Decarbonization in the United States (forthcoming in 2018 from ELI), asks why household behavior matters for deep decarbonization, and how laws, policies, and programs that target behavior change can be employed to facilitate decarbonization. The pathways set forth in the Deep Decarbonization Pilot Project (DDPP) all presume widespread public acceptance of new policies, as well as changes in household actions that directly affect carbon emissions, mainly via consumer adoption of technologies that have lower greenhouse gas footprints. The best available research indicates that achieving the rates of adoption included in the DDPP pathways is indeed feasible; however, this will require more than policies that require change or make adoption financially attractive. The most realistic analysis of the potential for change must consider the technical potential for change, the behavioral plasticity, and the policy plasticity, or the feasibility of adopting and implementing the most commonly recommended interventions.