assumptions, the committee judges that they are sufficiently robust to be useful for rough comparisons.

• The report does not provide an evaluation of the full range of options for reducing energy use. Such reductions are generally understood to be obtainable in two ways: (1) deploying technologies to improve the efficiency of energy production and use and (2) conserving energy through behavioral or lifestyle changes (e.g., taking public transportation to work rather than driving).¹⁷ The focus of this report is on the assessment of technologies that address the first factor—improving the efficiency of energy use. It addresses energy conservation only insofar as conservation is affected by the deployment of more energy-efficient technologies. To be sure, conservation is an important option for reducing energy use, but its detailed consideration is well beyond the technological scope of this study. A study on energy conservation would require, for example, an in-depth understanding of how social, economic, and policy factors affect energy consumption.

• The report does not provide forecasts of future prices of primary energy inputs (e.g., for petroleum and coal) or the effects of possible future policies and regulations concerning CO₂ emissions on such prices. Such prices, however, will influence the relative competitiveness of the energy-supply and end-use technologies discussed in this report, and they will affect technology choices and paces of development, especially in the private sector.

This chapter has briefly discussed the current characteristics of the U.S. energy system, the challenges to improving the system’s sustainability and security, the role of technology, and the committee’s strategy for addressing its study charge (Box 1.1). The next two chapters complete Part 1 of this report by providing sum-