In addition to developing alternative sources of energy, energy supplies can be extended by the conservation (the planned management) of currently available resources. Three types of possible energy conservation practices may be described. The first type is curtailment, that is, doing without—for example, closing factories to reduce the amount of power consumed or cutting back on travel to reduce the amount of gasoline burned. The second type is overhaul, that is, changing the way people live and the way goods and services are produced—for example, slowing further suburbanization of society, using less energy-intensive materials in production processes, and decreasing the amount of energy consumed by certain products (such as automobiles). The third type involves the more efficient use of energy, that is, adjusting to higher energy costs—for example, investing in cars that go farther per unit of fuel, capturing waste heat in factories and reusing it, and insulating houses. This third option requires less drastic changes in lifestyle, so governments and societies most commonly adopt it over the other two options.

By 1980 many people had come to recognize that increased energy efficiency could help the world energy balance in the short and middle term, and that productive conservation should be considered as no less an energy alternative than the energy sources themselves. Substantial energy savings began to occur in the United States in the 1970s, when, for example, the federal government imposed a nationwide automobile efficiency standard and offered tax deductions for insulating houses and installing solar energy panels. Substantial additional energy savings from conservation measures appear possible without dramatically affecting the way people live.