The petroleum refining industry in the United States is the largest in the world, providing inputs to virtually any economic sector, including the transport sector and the chemical industry. The industry operates 146 refineries (as of January 2004) around the country, employing over 65,000 employees. The refining industry produces a mix of products with a total value exceeding $151 billion. Refineries spend typically 50% of cash operating costs (i.e., excluding capital costs and depreciation) on energy, making energy a major cost factor and also an important opportunity for cost reduction. Energy use is also a major source of emissions in the refinery industry making energy efficiency improvement an attractive opportunity to reduce emissions and operating costs. Voluntary government programs aim to assist industry to improve competitiveness through increased energy efficiency and reduced environmental impact. ENERGY STAR®, a voluntary program managed by the U.S. Environmental Protection Agency, stresses the need for strong and strategic corporate energy management programs. ENERGY STAR® provides energy management tools and strategies for successful corporate energy management programs. This Energy Guide describes research conducted to support ENERGY STAR® and its work with the petroleum refining industry. This research provides information on potential energy efficiency opportunities for petroleum refineries. This Energy Guide introduces energy efficiency opportunities available for petroleum refineries. It begins with descriptions of the trends, structure, and production of the refining industry and the energy used in the refining and conversion processes. Specific energy savings for each energy efficiency measure based on case studies of plants and references to technical literature are provided. If available, typical payback periods are also listed. The Energy Guide draws upon the experiences with energy efficiency measures of petroleum refineries worldwide. The findings suggest that given available resources and technology, there are opportunities to reduce energy consumption cost-effectively in the petroleum refining industry while maintaining the quality of the products manufactured. Further research on the economics of the measures, as well as the applicability of these to individual refineries, is needed to assess the feasibility of implementation of selected technologies at individual plants.