Energy performance-based hookup fees, such as the current “gas-guzzler” tax for automobiles, have been suggested as a promising policy option for promoting energy efficiency in new vehicles, appliances, and buildings. Conceptually, these impact fees force manufacturers to consider the long-term energy implications of the products they produce. The article finds that implementation is not straightforward, particularly with respect to buildings. The absence of an unambiguous measure of a building's relative efficiency, such as the miles-per-gallon (mpg) rating for cars, and the inability to control fee avoidance by fuel switching, impede building hookup fee development. Performance-based impact fees for sewage, water supply, and stormwa-ter are workable, largely because their current fee structures are simpler.