This publication is one of a series on energy-efficient best practices for modern laboratories; it was prepared for''Laboratories for the 21st Century,'' a joint program of the Environmental Protection Agency and the U.S. Department of Energy Federal Energy Management Program. It is intended for those who plan, design, and construct public and private-sector laboratory buildings. The aim is to use the most energy-efficient and reliable strategies--such as combined heat and power systems, photovoltaics, and fuel cells--to produce power on site and reduce a laboratory's use of utility-generated power, as well as the greenhouse gases associated with burning fossil fuels for power production. Examples are included.