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Connecticut (US-CT)

Market Type: Hybrid (Limited Retail Choice)
SSS Relevance: ⭐⭐⭐ High
Grid Carbon Intensity: ~244 gCO₂/kWh

SSS Factors: significant nuclear capacity, hydroelectric resources

1. Overview​

Connecticut operates a partially deregulated electricity market within the ISO New England (ISO-NE) regional grid. The physical infrastructure (poles and wires) is owned and maintained by two investor-owned utilities, Eversource and United Illuminating (UI), which are regulated by the Public Utilities Regulatory Authority (PURA) 1. While consumers cannot choose their delivery utility, they can select their electricity generation supplier. Consumers are placed on a "Standard Service" plan by default but may switch to third-party competitive suppliers 1.

As of early 2026, Connecticut's electricity rates are among the highest in the U.S., trailing only Hawaii and California 2. High costs are largely driven by the state's heavy reliance on natural gas, which fuels approximately 58% to 61% of electricity generation 3. Nuclear power (specifically the Millstone Power Station) provides another 34% to 40% of the state's power, contributing to a low-carbon share of approximately 42% 3. The state's grid carbon intensity was measured at approximately 293 gCO2eq/kWh in early 2026 4.

Despite a robust regulatory framework, there is a significant gap between in-state renewable generation and consumption mandates. In-state renewable generation (solar, wind, hydro, biomass) accounts for only about 2.7% of electricity generated within the state. However, including "behind-the-meter" residential solar, solar energy provides approximately 4.85% of total electricity 5. Under state law, electric suppliers must meet escalating Renewable Portfolio Standard (RPS) targets, reaching 48% renewable energy by 2030 and a 100% zero-carbon electric supply by 2040 4. To meet these goals, the state is actively soliciting up to 2,000 MW of offshore wind capacity by 2030 4.

2. Market Structure​

Connecticut utilizes a deregulated electricity market where generation is separated from delivery. This structure allows residential and business customers to engage in retail choice, selecting third-party suppliers for energy supply while local utilities continue to manage delivery, maintenance, and billing. If customers do not choose a supplier, they automatically receive "Standard Service" from their utility, which purchases power on the open market and passes the cost to customers without a markup 6.

The state's transmission system and wholesale electricity markets are managed by the Independent System Operator – New England (ISO-NE). ISO-NE serves as the regional transmission organization (RTO) for six states, including Connecticut, managing over 9,000 miles of transmission lines and coordinating with more than 350 power plants 7. While ISO-NE handles the regional grid and wholesale market, the Connecticut Public Utilities Regulatory Authority (PURA) and the Department of Energy and Environmental Protection (DEEP) regulate retail electricity service and implement state-level policies 8.

Electric utilities in Connecticut are primarily divided into investor-owned utilities (IOUs) and municipal utilities. The two major IOUs are Eversource Energy and United Illuminating (UI), which serve the majority of the state's residents and are regulated by PURA 9. Municipal utilities, such as Groton Utilities and the Town of Wallingford Electric Division, are non-profit entities governed locally. Many of these municipalities participate in the Connecticut Municipal Electric Energy Cooperative (CMEEC), a joint action agency formed in 1976 to pool resources for purchasing wholesale power at lower costs 8.

Recent market dynamics have shown significant shifts in savings opportunities. In 2023, customers who switched to competitive suppliers totaled over $100 million in savings, contrasting with historical trends where many customers on third-party plans overpaid 10. To address high rates driven by reliance on natural gas and transmission costs, the state approved $150 million in borrowing in August 2025 to provide immediate rate relief, estimated at roughly $10 per month 10.

3. Clean Energy Policy​

Connecticut has established legally binding mandates to decarbonize its electricity sector and economy, primarily driven by the Renewable Portfolio Standard (RPS) and the Global Warming Solutions Act (GWSA).

Renewable Portfolio Standard (RPS) The RPS requires electric suppliers and distribution companies to source a specific percentage of their retail load from renewable energy sources. The standard is divided into three classes with distinct targets for 2030 11:

  • Class I (40%): Includes solar, wind, fuel cells, geothermal, and sustainable biomass.
  • Class II (4%): Includes trash-to-energy, older biomass, and certain hydropower.
  • Class III (4%): Focuses on energy efficiency and combined heat and power (CHP) systems.

Suppliers comply by procuring Renewable Energy Certificates (RECs), where one REC equals one megawatt-hour (MWh) of generation. Failure to meet requirements results in Alternative Compliance Payments (ACP), which are currently set at 4 cents per kWh for Class I 12 11.

Long-Term Climate Goals Connecticut law mandates a transition to 100% zero-carbon electricity by 2040 (Public Act 22-5) and economy-wide net-zero greenhouse gas emissions by 2050 13 14. Interim targets include reducing GHG emissions to 45% below 2001 levels by 2030 and 65% below 2001 levels by 2040 13.

Recent Legislation & Strategy Recent legislation (Public Acts 22-5 and 25-125) has expanded programs for solar energy storage, shared clean energy facilities, and electric vehicle infrastructure 13. To support grid reliability amid increasing demand from electrification, the state has set energy storage targets of 580 MW by 2030 and 1,000 MW by 2040 15.

⚠️ Current Progress: As of early 2026, state reports indicate that Connecticut is "not on track" to meet its 2030 and 2050 emissions targets, with projections showing only a 34% reduction in emissions by 2030 against the 45% goal 11.

4. Utility Landscape​

Connecticut's electric utility market is dominated by two investor-owned utilities (IOUs) that serve over 90% of the state's customers [1]. These companies are responsible for transmission and distribution infrastructure within a deregulated energy market where consumers can choose alternative retail suppliers for generation.

Investor-Owned Utilities (IOUs) The state's primary electric distribution companies are:

  • Eversource Energy: Formerly known as Connecticut Light and Power, it is the state's largest utility serving over 1.2 million customers [2].
  • United Illuminating (UI): A subsidiary of Avangrid, primarily serving the greater New Haven and Bridgeport areas [2].

Both electric IOUs are regulated by the Connecticut Public Utilities Regulatory Authority (PURA) [2].

Municipal Utilities and Cooperatives Several municipalities operate their own non-profit electric utilities, which are typically exempt from deregulation and often offer lower rates than major IOUs. Most of these utilities belong to the Connecticut Municipal Electric Energy Cooperative (CMEEC), a joint-action agency established in 1976 [3]. CMEEC is owned by six member utilities and provides wholesale power to approximately 70,000 customers [3].

Key municipal utilities include:

  • Norwich Public Utilities: Serves the city of Norwich [1].
  • Groton Utilities: Serves Groton and surrounding areas [1].
  • Wallingford Electric Division: Notable for residential rates often 30–40% lower than the major utilities [1].
  • South Norwalk Electric and Water (SNEW): Serves the Second Taxing District of Norwalk [1].
  • Jewett City Department of Public Utilities: A member-owner of CMEEC [3].
  • Bozrah Light & Power: A member-owner of CMEEC [3].
  • East Norwalk Electric Department: Serves the Third Taxing District and is a member-owner of CMEEC [3].

CMEEC manages power supply contracts and transmission assets through its subsidiary, TRANSCO, utilizing a portfolio that includes nuclear, hydroelectric, and fossil-fuel sources [3].

Alternative Retail Suppliers In the deregulated market, large competitive suppliers allow consumers to switch generation service while keeping Eversource or UI for delivery. Major suppliers include:

  • Constellation Energy: Serves over 150,000 customers in Connecticut [1].
  • Direct Energy: A major North American retailer [1].

5. SSS-Eligible Resources​

ResourceTypeCapacity (MW)SSS EligibleNotes
Millstone PowerNuclear870✅ YesOperating nuclear
Rocky RiverNuclear29✅ YesOperating nuclear

⚠️ Generation output is subject to environmental factors, such as drought conditions which can reduce regional daily output by up to 50% [ctriver.org +8].

6. EAC/REC Registry Infrastructure​

Connecticut utilizes the NEPOOL Generation Information System (NEPOOL-GIS) as its primary electronic registry for tracking Energy Attribute Certificates (EACs), commonly referred to as Renewable Energy Certificates (RECs) [1][2][3]. This regional platform issues a unique serial number for every megawatt-hour (MWh) of electricity generated to prevent double-counting and verify environmental attributes [1][2].

Regulatory Oversight and Classification​

The Public Utilities Regulatory Authority (PURA) oversees the state's Renewable Portfolio Standard (RPS) program, ensuring compliance with mandatory renewable energy requirements, including a target of a 38% minimum by 2025 [2]. To qualify for Connecticut's RPS, facilities must be certified by PURA into one of three specific classes [2][3]:

  • Class I: Solar, wind, fuel cells, and certain run-of-river hydroelectric or biomass facilities [2][3].
  • Class II: Trash-to-energy (municipal solid waste) facilities [2][3].
  • Class III: Combined heat and power (CHP) systems and energy efficiency projects [2][3].

Program Integration​

The NEPOOL-GIS infrastructure supports state-run incentive programs such as Residential Renewable Energy Solutions (RRES) and Non-Residential Renewable Energy Solutions (NRES). Under these programs, administered by utilities like Eversource and United Illuminating, participants typically transfer REC ownership to the utility in exchange for fixed-rate payments [2][3].

⚠️ Note on Inter-Registry Transfers: While NEPOOL-GIS is the state's primary system, search results indicate that broader market trading may involve imports or exports from other major North American registries (WREGIS, M-RETS, PJM-GATS), provided specific state eligibility rules are met [1]. The specific protocols for transferring RECs into Connecticut from these external systems are not detailed in the provided results.

7. Grid Emissions​

Generation Mix​

Scope 2 Reporting​

  • SB 253 requires Scope 2 reporting for companies >$1B revenue

Source: EPA eGRID, EIA, state regulatory filings

References​

Sources & Last Updated​

Research Date: 2026-03-10
Data Sources: EIA, EPA eGRID, state regulatory filings, SerpAPI research aggregation

This page was generated using automated research and may contain inaccuracies. Verify critical data with primary sources.

Footnotes​

  1. United Illuminating ↩ ↩2

  2. CT Mirror ↩

  3. Climate Policy Dashboard ↩ ↩2

  4. CT.GOV-Connecticut's Official State Website (.gov) ↩ ↩2 ↩3

  5. Solar Energy Industries Association ↩

  6. Energy Choice Services ↩

  7. Federal Energy Regulatory Commission (.gov) ↩

  8. C G A - Connecticut General Assembly (.gov) ↩ ↩2

  9. Energy and Policy Institute ↩

  10. Nealon Insulation ↩ ↩2

  11. CT.GOV-Connecticut's Official State Website ↩ ↩2 ↩3

  12. National Conference of State Legislatures ↩

  13. C G A - Connecticut General Assembly ↩ ↩2 ↩3

  14. CT Energy Future ↩

  15. RPA | Regional Plan Association ↩