The economic and environmental benefits of efficiency are typically assessed assuming that all consumers use appliances in the same way. There are, however, significant differences in consumer usage patterns, as well as geographical variability in prices and environmental impacts of electricity. To explore the importance of heterogeneity, we first develop distributions of consumer-by-consumer economic benefits from purchasing an efficient versus standard appliance for televisions, clothes washers, and dryers in the U.S. We find large variability, e.g. for washers and dryers, 9% and 7.5% of the U.S. population do not save money over the lifetime of an efficient device, while 11% and 17% save more than twice that of an average consumer. Providing personalized savings information can thus inform and better motivate those consumers who would save more. Abatement costs for carbon and electricity use are similarly heterogenous as consumer economic benefits, indicating that adoption by heavy users is in the public as well as private interest. The cost of abating carbon via a utility appliance rebate program varies greatly by consumer. To scope the emission benefits of targeted adoption, we find that adoption by heavy users saves around 3 times more carbon than an average user for 10% participation in an efficiency program.