FIGURE S.1 Total U.S. energy use by sector, 2008 (in quadrillion Btu, or quads). For each sector, “total energy use” is direct (primary) fuel use plus purchased electricity plus apportioned electricity-system losses. Economy-wide, total U.S. primary energy use in 2008 was 99.4 quads. Totals may not equal sum of components due to independent rounding.

Source: EIA 2009a, as updated by EIA, 2009b.

continues to develop, the panel was also asked to look beyond 2035 in assessing the technological potential for increasing U.S. energy efficiency.

Although the terms “energy efficiency” and “energy conservation” are often used interchangeably, they refer to different concepts. Improving energy efficiency involves accomplishing an objective—such as heating a room to a certain temperature—while using less energy. Energy conservation can involve changing one’s behavior so as to use less energy—e.g., driving a smaller car, or lowering the thermostat in winter. The panel’s work focused on technology and energy efficiency, rather than energy conservation.

As a result of its broad look at energy use in other nations (Chapter 1); a detailed examination of the buildings (Chapter 2), transportation (Chapter 3), and industrial (Chapter 4) sectors and of numerous studies of energy use and poten-