Energy-efficiency laws and policies have great ability to improve economic wellbeing and human health, while reducing the adverse effects of energy use on climate and the environment generally. New Zealand, like many countries, has a legal framework for energyefficiency measures, including a specialist agency, a process for strategic planning and the making of regulations. This framework has certain strengths, but shows deficiencies in its use of strategies. Its use of regulation for labelling and minimum energy performance standards is similar to that of a number of other countries. In this article, New Zealand law on energyefficiency is compared with that of California and Germany. Insights from social sciences and behavioural economics have considerable promise in the design of energy-efficiency measures. However, a clear legal framework is necessary to put energy efficiency at the heart of energy policy, and to pursue it with conventional legal regulatory measures.