| PRICE GREGORY INTERNATIONAL, INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | Jun 21, 1985 | Withdrawn |
| J.C.R. CONSTRUCTION CO., INC.Location not reported, CT · Active | Location not reported, CT | Corporation | May 23, 1996 | Active |
| CROCE ELECTRIC COMPANY, INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | May 16, 2000 | Withdrawn |
| THE RYAN COMPANY INC. OF MASSACHUSETTSLocation not reported, CT · Active | Location not reported, CT | Corporation | May 19, 2000 | Active |
| PAR ELECTRICAL CONTRACTORS, INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | Nov 8, 2001 | Withdrawn |
| WILSON CONSTRUCTION CO.Location not reported, CT · Active | Location not reported, CT | Corporation | Sep 8, 2003 | Active |
| MEARS GROUP, INC.Location not reported, CT · Active | Location not reported, CT | Corporation | May 16, 2006 | Active |
| NORTH AMERICAN INDUSTRIAL SERVICES, INC.Location not reported, CT · Active | Location not reported, CT | Corporation | Nov 28, 2006 | Active |
| WINCO, INC.Location not reported, CT · Active | Location not reported, CT | Corporation | Apr 10, 2007 | Active |
| REALTIME UTILITY ENGINEERS, INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | Jul 3, 2007 | Withdrawn |
| DASHIELL CORPORATIONLocation not reported, CT · Active | Location not reported, CT | Corporation | Feb 8, 2010 | Active |
| QUANTA ELECTRIC POWER CONSTRUCTION MANAGEMENT, INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | Jul 28, 2011 | Withdrawn |
| CUPERTINO ELECTRIC, INC.Location not reported, CT · Active | Location not reported, CT | Corporation | Jul 2, 2013 | Active |
| POTELCO, INC.Location not reported, CT · Active | Location not reported, CT | Corporation | Apr 16, 2014 | Active |
| CRUX SUBSURFACE, INC.Location not reported, CT · Active | Location not reported, CT | Corporation | Jan 21, 2015 | Active |
| QUANTA POWER GENERATION, INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | Jun 10, 2015 | Withdrawn |
| CANACRE (U.S.A.) INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | Mar 17, 2016 | Withdrawn |
| QUANTA UTILITY ENGINEERING SERVICES, INC.Location not reported, CT · Withdrawn | Location not reported, CT | Corporation | Jan 12, 2018 | Withdrawn |
| THE HALLEN CONSTRUCTION CO., INC.Location not reported, CT · Active | Location not reported, CT | Corporation | Aug 22, 2019 | Active |
| Sherman + Reilly Inc.Location not reported, CT · Active | Location not reported, CT | Corporation | Feb 15, 2023 | Active |
| D.H. Blattner & Sons, LLCLocation not reported, CT · Active | Location not reported, CT | LLC | Jun 18, 2026 | Active |
| APEX POWER SOLUTIONS, LLCLocation not reported, CT · Active | Location not reported, CT | LLC | Jun 19, 2026 | Active |
| QSI, Inc.Location not reported, CT · Active | Location not reported, CT | Corporation | Oct 6, 2026 | Active |