sentences:  This prevented the growth experienced in the late 1970s from continuing.The industry grew slowly through the 1970s and 1980s, spurred by specialist firms such as Hospital Efficiency Corporation (HEC Inc.), established in 1982 to focus on the energy intensive medical sector.HEC Inc., later renamed Select Energy Services, was acquired in 1990 by Northeast Utilities, and sold in 2006 to Ameresco.