Energy law and energy policy, to which Adrian Bradbrook has contributed so much, are significant for several reasons. The first reason, very relevant to the concern of this chapter, is to meet human needs. In New Zealand dwelling-houses are often colder than international standards stipulate, and that causes health problems, especially for the young, the old and other vulnerable members of the population. The second main reason is the significant adverse effect on the environment of the production of energy and its use. The third reason is climate change; energy production is the main source of greenhouse gas emissions.

While energy law and policy can focus on change in the way that energy is supplied, such as by increasing renewable energy supplies, the demand side requires much more attention; in fact, the demand side, including energy efficiency, is where the big gains are to be made. In climate change terms, this important truth has been demonstrated by comprehensive studies by the International Energy Agency in its annual World Energy Outlook. It estimates that if governments worldwide put in place policies to stabilise atmospheric concentrations of carbon dioxide at 450 parts per million, then 57 per cent of the change would come from energy efficiency measures. Another study shows that the most cost-effective technologies to reduce greenhouse gas emissions are efficiency measures; in fact, many efficiency measures have a negative cost.