The economic models that prescribe Pigovian taxation as the first-best means of reducing energy-related externalities are typically based on the neoclassical model of rational consumer choice. Yet, consumer behavior in markets for energy-using durables is generally thought to be far from efficient, giving rise to the concept of the �energy-efficiency gap.� This paper presents a welfare analysis of energy policies that is based on a behavioral model of temptation and self-control, introduced by Gul and Pesendorfer [23] and [24]. We find that, in the presence of temptation, (i) Pigovian taxes alone do not yield a first-best outcome, (ii) when viewed as substitutes, energy efficiency standards can dominate Pigovian taxes, and (iii) a policy combining standards with a Pigovian tax can yield higher social welfare than a Pigovian tax alone, implying that the two instruments should be viewed as complements rather than substitutes.