Electric utilities in Connecticut
Every electric utility serving Connecticut in EIA data year 2025, with ownership type, grid operator, balancing authority, customers and the counties each one serves.
Retail electric utilities in Connecticut
Sorted by customers. See Connecticut on the map, and the state regulator, Public Utilities Regulatory Authority.
| Utility | EIA ID | Type | ISO or region | Balancing authority | Customers | Counties served |
|---|---|---|---|---|---|---|
| Connecticut Light & Power CoEversource (Connecticut Light & Power) | 4176 | Investor-owned | ISO-NE | ISNE | 1,251,052 | 8 Fairfield, Hartford, Litchfield, Middlesex, New Haven, New London, Tolland, Windham |
| United Illuminating CoUnited Illuminating (Avangrid) | 19497 | Investor-owned | ISO-NE | ISNE | 336,008 | 2 Fairfield, New Haven |
| Town of Wallingford - (CT) | 20038 | Municipal | ISO-NE | ISNE | 25,026 | 1 New Haven |
| City of Norwich - (CT) | 13831 | Municipal | ISO-NE | ISNE | 20,298 | 1 New London |
| Groton Dept of Utilities - (CT) | 7716 | Municipal | ISO-NE | ISNE | 13,766 | 1 New London |
| City of South Norwalk - (CT) | 17569 | Municipal | ISO-NE | ISNE | 6,778 | 1 Fairfield |
| Norwalk Third Taxing District | 13825 | Municipal | ISO-NE | ISNE | 3,858 | 1 Fairfield |
| Bozrah Light & Power Company | 2089 | Municipal | ISO-NE | ISNE | 2,763 | 1 New London |
| City of Jewett City - (CT) | 9734 | Municipal | ISO-NE | ISNE | 2,193 | 1 New London |
| Mohegan Tribal Utility Authority | 49826 | Public power district | ISO-NE | ISNE | 79 | 1 New London |
| Farmington River Power Company | 6207 | Investor-owned | ISO-NE | ISNE | 1 | 1 Hartford |
| Connecticut Mun Elec Engy Coop | 4180 | Joint action / municipal marketing | ISO-NE | — | — | 0 — |
Which utilities serve each county in Connecticut
| County | FIPS | ISO or region | Utilities | Utilities serving the county |
|---|---|---|---|---|
| Fairfield | 09001 | ISO-NE | 4 | United Illuminating Co, Connecticut Light & Power Co, City of South Norwalk - (CT), Norwalk Third Taxing District |
| Hartford | 09003 | ISO-NE | 2 | Connecticut Light & Power Co, Farmington River Power Company |
| Litchfield | 09005 | ISO-NE | 1 | Connecticut Light & Power Co |
| Middlesex | 09007 | ISO-NE | 1 | Connecticut Light & Power Co |
| New Haven | 09009 | ISO-NE | 3 | United Illuminating Co, Connecticut Light & Power Co, Town of Wallingford - (CT) |
| New London | 09011 | ISO-NE | 6 | Connecticut Light & Power Co, City of Norwich - (CT), Groton Dept of Utilities - (CT), Bozrah Light & Power Company, City of Jewett City - (CT), Mohegan Tribal Utility Authority |
| Tolland | 09013 | ISO-NE | 1 | Connecticut Light & Power Co |
| Windham | 09015 | ISO-NE | 1 | Connecticut Light & Power Co |
Retail power marketers and other entities in Connecticut
Competitive suppliers, wholesale marketers, transmission-only companies and behind-the-meter providers that report to EIA for Connecticut. They have no county service territory of their own.
| Entity | EIA ID | Type | ISO or region | Customers |
|---|---|---|---|---|
| Ambit Energy Holdings, LLC | 56212 | Retail power marketer | ISO-NE | 51,146 |
| Constellation NewEnergy, Inc | 13374 | Retail power marketer | ISO-NE | 50,492 |
| Direct Energy Services | 54820 | Retail power marketer | ISO-NE | 41,228 |
| Public Power LLC (CT) | 58119 | Retail power marketer | ISO-NE | 38,026 |
| North American Power and Gas, LLC | 58667 | Retail power marketer | ISO-NE | 36,333 |
| Think Energy, LLC | 65310 | Retail power marketer | ISO-NE | 30,472 |
| Town Square Energy | 59059 | Retail power marketer | ISO-NE | 28,483 |
| Clearview Electric Inc. | 58974 | Retail power marketer | ISO-NE | 26,076 |
| Discount Power Inc - (CT) | 59993 | Retail power marketer | ISO-NE | 21,537 |
| Spark Energy, LP | 17710 | Retail power marketer | ISO-NE | 15,290 |
| Verde Energy USA | 59620 | Retail power marketer | ISO-NE | 15,203 |
| SolarCity Corporation | 57313 | Behind-the-meter provider | ISO-NE | 9,321 |
| Direct Energy Business | 18193 | Retail power marketer | ISO-NE | 9,121 |
| XOOM Energy Connecticut, LLC | 57487 | Retail power marketer | ISO-NE | 6,380 |
| Reliant Energy Northeast LLC | 57037 | Retail power marketer | ISO-NE | 6,237 |
| Viridian Energy LLC | 58161 | Retail power marketer | ISO-NE | 5,779 |
| Energy Services Providers, Inc | 55874 | Retail power marketer | ISO-NE | 4,647 |
| Sunrun Inc. | 59647 | Behind-the-meter provider | ISO-NE | 4,296 |
| Choice Energy, LLC d/b/a 4 Choice Energy | 59055 | Retail power marketer | ISO-NE | 2,840 |
| Energy Plus Holdings LLC | 56265 | Retail power marketer | ISO-NE | 2,782 |
| Major Energy Electric Services | 56504 | Retail power marketer | ISO-NE | 2,271 |
| Sunnova | 59579 | Behind-the-meter provider | ISO-NE | 1,986 |
| Palmetto Solar, LLC | 66026 | Behind-the-meter provider | ISO-NE | 1,864 |
| EverBright, LLC | 66036 | Behind-the-meter provider | ISO-NE | 1,352 |
| First Point Power, LLC | 59793 | Retail power marketer | ISO-NE | 842 |
| SunPower Capital, LLC | 59580 | Behind-the-meter provider | ISO-NE | 741 |
| Greenbacker Renewable Energy Corporation | 60025 | Behind-the-meter provider | ISO-NE | 599 |
| NextEra Energy Services, LLC | 7279 | Retail power marketer | ISO-NE | 592 |
| ENGIE Resources LLC | 19107 | Retail power marketer | ISO-NE | 433 |
| BP Energy Retail LLC | 64314 | Retail power marketer | ISO-NE | 229 |
| SmartestEnergy US LLC | 63356 | Retail power marketer | ISO-NE | 219 |
| Spruce Finance | 59943 | Behind-the-meter provider | ISO-NE | 166 |
| Eligo Energy, LLC | 59054 | Retail power marketer | ISO-NE | 155 |
| Atlantic Energy LLC | 60583 | Retail power marketer | ISO-NE | 89 |
| Champion Energy Services | 54862 | Retail power marketer | ISO-NE | 62 |
| Texas Retail Energy, LLC | 50046 | Retail power marketer | ISO-NE | 53 |
| Calpine Energy Solutions, LLC | 16840 | Retail power marketer | ISO-NE | 42 |
| Grid Power Direct, LLC | 64222 | Retail power marketer | ISO-NE | 10 |
| TerraForm US Energy Services, LLC | 60981 | Behind-the-meter provider | ISO-NE | 7 |
| Greenskies Renewable Energy, LLC | 61823 | Behind-the-meter provider | ISO-NE | 2 |
| Constellation Solar Holding, LLC | 59086 | Behind-the-meter provider | ISO-NE | 1 |
| DCR Transmission, LLC | 66923 | Transmission-only | CAISO | — |
| HQ Energy Services (US), Inc | 21249 | Wholesale marketer | ISO-NE | — |
About this data
Which utilities exist comes from the U.S. Energy Information Administration’s Form EIA-861 and EIA-861S, data year 2025 (final release, October 7, 2026), read directly from eia.gov. County service territories, balancing authority codes and customer counts come from EIA-861 for 2018, the latest year compiled at county level for this directory; utilities that started reporting after 2018 carry their 2025 values. County boundaries are U.S. Census cartographic boundaries (us-atlas 3.0, Albers USA projection).
Customer counts are per utility within Connecticut. A county’s grid operator is the one serving most of its customers, estimated by spreading each utility’s customers evenly over its counties. Download every state in one file from the U.S. Electric Utility Directory.
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