Ameresco, Inc. is a provider of energy efficiency solutions for facilities throughout North America. Its services include upgrades to a facility's energy infrastructure and the construction and operation of small-scale renewable energy plants. Its principal service is the development, design, engineering and installation of projects that reduce the energy and operations and maintenance (O&M) costs of its customers' facilities. These projects include a variety of measures customized for the facility and designed to improve the efficiency of major building systems, such as heating, ventilation, air conditioning and lighting systems. It also serves certain customers by developing and building small-scale renewable energy plants located at or close to a customer's site. It has four segments: U.S. federal, central U.S. region, other U.S. regions and Canada. In December 2011, it acquired the xChange Point and energy projects businesses, of Energy and Power Solutions, Inc.