| TECO HOLDINGS, INC.Tampa, FL · Active | Tampa, FL | Corporation | Feb 23, 2024 | Active |
| TECO GAS OPERATIONS, INC.Tampa, FL · Active | Tampa, FL | Corporation | Dec 15, 2022 | Active |
| BLOCK ENERGY SERVICE COMPANY, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Jun 8, 2021 | Inactive |
| BLOCK ENERGY PROJECT COMPANY, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Sep 17, 2020 | Inactive |
| SECI MITLAND CORPORATIONTampa, FL · Active | Tampa, FL | Corporation | Nov 8, 2019 | Active |
| TECO CLEAN ADVANTAGE CORPORATIONTampa, FL · Active | Tampa, FL | Corporation | Feb 14, 2012 | Active |
| SEACOAST GAS TRANSMISSION, LLCTampa, FL · Active | Tampa, FL | LLC | Jun 4, 2008 | Active |
| TECO GEMSTONE, INC.Tampa, FL · Active | Tampa, FL | Corporation | Nov 26, 2007 | Active |
| TECO COALBED METHANE FLORIDA, INC.Tampa, FL · Active | Tampa, FL | Corporation | Dec 23, 2002 | Active |
| TECO PARTNERS, INC.Tampa, FL · Active | Tampa, FL | Corporation | Sep 1, 2000 | Active |
| TAMPA ELECTRIC COMPANYTampa, FL · Active | Tampa, FL | Corporation | Apr 18, 1949 | Active |
| PEOPLES GAS SYSTEM (FLORIDA), INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Mar 29, 1956 | Inactive |
| TECO PROPERTIES CORPORATIONTampa, FL · Active | Tampa, FL | Corporation | Jul 26, 1966 | Active |
| TECO ENERGY, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Jan 16, 1981 | Inactive |
| TECO INVESTMENTS, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | May 4, 1987 | Inactive |
| TECO FINANCE, INC.Tampa, FL · Active | Tampa, FL | Corporation | May 4, 1987 | Active |
| TECO WHOLESALE GENERATION, INC.Tampa, FL · Active | Tampa, FL | Corporation | May 26, 1987 | Active |
| TECO DIVERSIFIED, INC.Tampa, FL · Active | Tampa, FL | Corporation | Oct 15, 1987 | Active |
| TECO PIPELINE HOLDING COMPANY, LLCTampa, FL · Inactive | Tampa, FL | LLC | May 20, 2008 | Inactive |
| TECO GUATEMALA, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | May 4, 2004 | Inactive |
| TECO SERVICES, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Oct 18, 2013 | Inactive |
| PEOPLES GAS SYSTEM, INC.Tampa, FL · Active | Tampa, FL | Corporation | May 24, 2021 | Active |
| TECO OIL & GAS, INC.Tampa, FL · Active | Tampa, FL | Corporation | Apr 7, 1995 | Active |
| DIAL-A-VIEW OF TAMPA BAY, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Jul 6, 1995 | Inactive |
| WARREN CONSULTING SERVICES, INC.Clearwater, FL · Inactive | Clearwater, FL | Corporation | Sep 21, 1995 | Inactive |
| WARREN MANAGEMENT COMPANY, INC.Clearwater, FL · Inactive | Clearwater, FL | Corporation | Sep 21, 1995 | Inactive |
| VENEZUELA USA TRADE COMPANYLocation not reported, FL · Inactive | Location not reported, FL | Corporation | Feb 6, 1996 | Inactive |
| ADGALS SOUTHEAST, INC.Celebration, FL · Inactive | Celebration, FL | Corporation | Feb 23, 1996 | Inactive |
| TECO ENERGYSOURCE, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Apr 15, 1996 | Inactive |
| B&B ACQUISITION CORP.Fernandina Beach, FL · Inactive | Fernandina Beach, FL | Corporation | Apr 30, 1997 | Inactive |
| WESTSTAR ACQUISTION CORP.Fernandina Beach, FL · Inactive | Fernandina Beach, FL | Corporation | Apr 30, 1997 | Inactive |
| ELECTRIC VEHICLE POWER, INC.Tampa, FL · Inactive | Tampa, FL | Corporation | Nov 5, 1997 | Inactive |