Ameresco Inc. is an energy service company. Ameresco is the largest independent energy services company in North America. It has participated in energy projects in the government, healthcare, public, and education sectors. Ameresco claims experience in demand-side management, energy savings performance contracts, cogeneration facilities, renewable energy sources, energy procurement, risk management, billing services and power plant development, financing, construction and operations.

The corporate office of Ameresco is based in Framingham, Massachusetts. They also have offices throughout the US and Canada.

Ameresco was founded by George Sakellaris, industry pioneer and founder of two previous successful energy services companies.

These major acquisitions have fueled Ameresco's aggressive growth strategy:

Citizens Conservation Services, established in 1981, is the nation's preeminent energy services company (ESCO) serving private and public multifamily properties. Since the group was first capitalized in 1995, current Citizens staff have implemented contracts with project capital of over $64 million—more than any other North American ESCO in this sector. Citizens' personnel have improved 30,000 households under performance-based energy and water services contracts, from California to New York.

DukeSolutions, the former energy management subsidiary of Duke Energy, was established in 1997 to serve end-user needs in a deregulating energy marketplace. DukeSolutions was one of the industry leaders in providing ownership, operation and maintenance of utility systems in North America—one of the few energy services providers with a significant customer base of Fortune 500 industrials and commercials. DukeSolutions' acquisitions included two long established firms:

Ameresco and its component companies have successfully completed energy solutions projects for approximately 300 customers involving over 9,000 facilities and resulting in substantial energy and operating cost savings.

Enertech, a former ESCO subsidiary of LG & E Energy, was founded in 1995. With customers that include industrial, commercial, educational and healthcare facilities, Enertech has become a leader in the educational and healthcare market, focusing its services primarily in the mid to southeast region and provides comprehensive service to upgrades and building modernization.

E·Three, formerly a Sierra Pacific Resources company, was founded in 1997 and is an energy consulting and services company with offices in Nevada and California serving the Western States. E·Three also did business as E·Three Custom Energy Solutions in Las Vegas, and independent Energy Consulting, Inc. in California.

Select Energy Services, Inc. (SESI). Founded in 1982, SESI was a fully integrated energy-services company and in energy-efficiency engineering. SESI provided comprehensive energy engineering, efficiency, design, installation, and maintenance services, as well as water improvement systems, to a wide range of government and private-sector clients. SESI developed projects valued at more than a total of $1.0 billion.

Southwest Photovoltaic (SWPV) was founded in 1986 and was one of the original Authorized Distributors in North America for Solarex Corporation, a wholly owned subsidiary of Amoco Corporation. Solarex had developed many cost saving manufacturing innovations centered on its patented SEMIX polycrystalline cell delivering the first significant cost savings for volume manufactured PV modules in North America. SWPV was then able to take the Solarex product line of PV modules and develop many new customers and innovative off grid applications within the industrial and rural electrification emerging markets within North America.

Then, in 1996 Amoco Corp. was merged into British Petroleum (BP) thus creating one of the largest PV module manufacturing and technology companies in the world. SWPV thus became a BP Solar Distributor and in 2002 was named a Premier Distributor for BP Solar. In 2006, SWPV was named the largest volume distributor for BP Solar in North America.

Southwest Photovoltaic is now known as Ameresco Solar.

Global Energy was a leading renewable energy distribution corporation. They offered the design and supply of renewable energy products. They offered turnkey system sizing and integration of balance of systems.

Global Energy is now known as PV Energy Solutions.

The company sponsors student teams from Stanford University and Newburgh Free Academy (High School) that design, build and race solar powered cars as part of the Dell-Winston School Solar Car Challenge.

According to [1], Ameresco has joined the American College & University Presidents Climate Commitment (ACUPCC) as a sponsor in an effort to bring their sustainable, clean energy services to campuses across America.

Ameresco is also involved with the new Discovery Communications television series Battleground Earth starring Ludacris and Tommy Lee which airs on Planet Green.