Permitting energy infrastructure in Connecticut is a relatively straight-forward process. Overseen by the Connecticut Siting Council (CSC), all energy infrastructure projects must obtain a Certificate of Environmental Compatibility and Public Need, and certain projects also require other relevant permits from the state’s Department of Energy and Environmental Protection. The CSC operates separately from the state’s public utility commission and generally issues or rejects permits between 180 days to one year after an application has been deemed complete. The permitting process ensures that a project complies with the state’s values and all local and state regulations, as well as federal regulations, where applicable.

The main body for energy infrastructure permitting in Connecticut is the Connecticut Siting Council (CSC). The Council is responsible for the siting of energy infrastructure as well as hazardous waste facilities. The Council provides environmental standards that are on par with or more stringent than federal standards and seeks to balance needs and costs. The Council, established in 1972 and formed into its current entity in 1981, is made up of nine members. Five members are appointed by the Governor, one by the Speaker of the House, one by the President Pro-temporre of the Senate, and the last is the Department of Energy and Environmental Protection (DEEP) Commissioner. Two members appointed by the governor must have ecology experience and only one member can have affiliation with a utility or government utility regulatory agency. Unlike siting councils in other states, the CSC does not sit under the state’s public utility commission, the Public Utilities Regulatory Authority (PURA), since all the commissioners are appointed by various elected officials, rather than hired. As a result, there can be knowledge gaps in utility and energy regulation on the Council, leading to clustering of energy infrastructure in certain geographies or seemingly arbitrary approvals or denials of applications. The CSC also has dedicated permanent staff who review applications.

All energy generation and transmission projects must obtain approval through the CSC in the form of a Certificate of Environmental Compatibility and Public Need (Certificate). This Certificate allows the construction to proceed and operations and maintenance activities to continue during the lifespan of the project. The process to obtain a Certificate varies slightly depending on the project type, mostly in terms of duration.

Transmission: Transmission projects, including offshore wind transmission, must go through a pre-application process before they can submit an application. The first stage of this process is municipal consultation, which entails former consultations of all host municipalities and adjoining municipalities at least 90 days before an application is submitted. Filed applications must pay a filing fee, which is dependent on the estimated construction costs, but does not exceed $25,250.00. Applicants must also submit a fee of $40,000 - $80,000 for municipal participation. Within 30 days of the submission of an application, developers must apply to any relevant municipal zoning and inland wetland agencies. Those authorizations or denials can be appealed within 30 days. Also within 30 days, the Council must determine if an application is complete, and may reject an application if it is deemed incomplete. At least one public hearing must be held. The Council must issue a permit or reject the application within 12 months of the application being filed. There is also an option for a petition for a declaratory ruling. This process allows a project to move forward without receiving a Certificate of Environmental Compatibility and Public Need, although significant data and argument is needed to ensure the project will not cause harm.

Electric Generation and Battery Storage: Similar to transmission projects, electric generation (including fossil and renewable projects) and battery storage projects must go through a pre-application process before they can submit an application. The municipal consultation process has the same requirements, although it is shorter - it has to be started at least 60 days prior to the application submission. Filed applications must pay a filing fee, which is dependent on the estimated construction costs, but does not exceed $25,250.00. Applicants must also submit a fee of $40,000 - $80,000 for municipal participation. Within 30 days of the submission of an application, developers must apply to any relevant municipal zoning and inland wetland agencies. Those authorizations or denials can be appealed within 30 days. Also within 30 days, the Council must determine if an application is complete, and may reject an application if it is deemed incomplete. At least one public hearing must be held. The Council must issue a permit or reject the application within 180 days of the application being filed. As with Transmission projects,here is also an option for a petition for a declaratory ruling.

There is no explicit permitting process for new nuclear generation in Connecticut. Since the last reactor was built in the early 1970s, there is no modern precedent for a new reactor in the state. If Connecticut moves forward with their plans to build new advanced nuclear power, they must decide whether to create new permitting regulations or add nuclear power into the existing electric generation permit.

Natural Gas: On top of the Certificate process described above, natural gas facilities are required to have a number of air-specific permits and compliance agreements administered by DEEP. These include a Combined Heat and Power Notification; Continuous Emissions Monitoring permit; Emissions Inventory agreement; Emissions Reduction and Trading agreement; Fuel Use and Hours of Operation agreement; Nitrogen Oxides Reduction and Control permit; and Stack and CEMS Performance Testing agreement.

Once a certificate is approved, which can take between six and twelve months, energy projects must submit a Development and Management Plan. This plan includes reporting requirements, both to the public and the Council. The Council has 60 days to approve, amend, or deny the plan once submitted.

Despite a strict adherence to the schedule as written, the CSC is not without controversy. There have been recent cases where Connecticut Siting Council approvals have been overturned by the State’s Superior Court. The most recent example was a transmission line project in Fairfield, where the Judge ruled that the CSC did not provide enough public notice and did not follow proper procedure when a change to the project was not publicly disclosed.

The remainder of state-level environmental permits are administered through the Connecticut Department of Energy and Environmental Protection (DEEP). There are three types of environmental permits that DEEP administers: Individual permits, general permits, and permit by rule.

Individual permits are for projects that are not covered by the general permits or permit by rule and may significantly impact air, water, or land. Individual permits require a pre-application meeting with DEEP and an environmental justice plan prior to the application submission. After the application is submitted, public hearings and comments commence while both a general and technical review is taking place. Once the review is completed and the public comment period is over, a draft permit will be issued. Public comments will be reviewed once again, and once incorporated, a permit will be issued. Individual permits include New Source Review Permit; Title V and Title IV permits; Aquifer Protection Area Permit; Coastal Activities Certificate of Permission; Flood Management Certification; Inland Wetlands and Watercourses (with 401 Water Quality Certification and Section 404); Section 401 Water Quality Certificate; and Water Diversion Non-Consumptive. These permits have different processing timelines, but are generally between three and 12 months.

General permits and permits by rule are for projects that will have minor impacts on air, water, or land. This process is quicker than the process for individual permits. Some projects may require pre-authorization and certification from a professional engineer, but do not require public hearings. Combined heat and power generators and distributed generators qualify for permit by rule. General permits include Contaminated Soil and/or Sediment Management permit; Stormwater and Dewatering Wastewaters from Construction Activities permit; Stormwater Associated with Industrial Activities permit; and Coastal Maintenance permit. Most of these permits take around three months to process, however a few take around six months to process.

Several projects have gone through the CSC process over the past two years, most of which were solar. Some projects have started the process but ended up withdrawing, either due to public pushback or an inability to get a permit. Examples of projects that have been approved or withdrawn include:

• Greenskies Clean Energy, LLC: Greenskies Clean Energy is a 4.99 MW solar farm located in Stonington, Connecticut. The initial application was submitted in September 2024. The application was approved in February 2025 after one set of comments was resolved. The project is currently under construction.

• Gravel Pit Solar: Gravel Pit Solar is a 120 MW solar farm located in East Windsor, Connecticut. The initial application was filed in July 2020. An initial permit was issued in March 2021 after significant public pushback. In April 2025, the developer submitted an application to expand the project by up to 30 MW. That application was approved March 2026, after several public hearings. The project is currently under construction.

• Windham Energy Center, LLC: Windham Energy Center is a 325 MW Battery Energy Storage Project in Killingly, Connecticut. The initial application was filed in October of 2024. The application was deemed incomplete in November 2024. Over the next three months, the developer requested additional time to complete the application. In June 2025, the developer submitted a Notice to Withdraw, effectively cancelling the project, citing changing conditions.

To address developer concerns around permitting timelines, DEEP released their ​“20 by 26” initiative in 2025. This initiative seeks to implement 20 specific improvements across the entire agency that increase the ​“predictability, efficiency, and transparency of DEEP’s processes. Specific initiatives include achieving a 90% on-time completion rate for permits, enhancing public records transparency, and speeding up permitting for decarbonization. To aid in these efforts, DEEP released a permitting timeline dashboard to make the process more transparent. As of Q1 2026, there have been significant reductions in permitting backlogs, particularly for 12 month air permits. For renewable energy projects, DEEP created a Community Renewable Energy Siting Tool (CREST), which improves public transparency by showing both where potential projects are being sited with grid interconnection maps.