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Interconnection Standards

Fed. Government
Local Government
State Government
Savings Category 
Fuel Cells
Fuel Cells using Renewable Fuels
Program Info
Program Type 
Public Utilities Regulatory Authority

In December 2007, the Connecticut Department of Public Utility Control (DPUC) now called the Public Utilities Regulatory Authority (PURA) approved new interconnection guidelines for distributed energy systems up to 20 megawatts (MW) in capacity. Connecticut's interconnection guidelines apply to the state's two investor-owned utilities -- Connecticut Light and Power Company (CL&P) and United Illuminating Company (UI) -- and are modeled on the Federal Energy Regulatory Commission's (FERC) interconnection standards for small generators.*

Connecticut's interconnection guidelines, like FERC's standards, include provisions for three levels of systems:

  • Certified, inverter-based systems no larger than 10 kilowatts (kW) in capacity (application fees: $100);
  • Certified systems no larger than 2 megawatts (MW) in capacity (application fees: $500); and
  • All other systems no larger than 20 MW in capacity. Note that the guidelines include "additional process steps" for generators greater than 5 MW (application fees: $1000, study fees will also apply).

Connecticut's guidelines include a standard interconnection agreement and application fees that vary by system type. However, Connecticut's guidelines are stricter than FERC's standards, differing from the federal standards in several significant ways:

  • Customers are required to install an external disconnect switch and an interconnection transformer.
  • Customers must indemnify their utility against "all causes of action," including personal injury or property damage to third parties.
  • Customers are required to maintain liability insurance in specified amounts based on the system's capacity.
  • In addition, the utilities were required to collaboratively submit to the PURA a status report on the research and development of area network interconnection standards. This report was completed in December 2009, and the PURA has reached a final decision ([ 03-01-15RE02]) on the docket. The PURA has determined that the utilities can interconnect inverter-based generators (up to 50 kW) on area networks.

The guidelines address requirements for study fees and include technical screens for each level of interconnection. Utilities and customers must follow general procedural timelines.

* [¤tpageid=1&ee=1&re=1 FERC's interconnection standards] are applicable to generator interconnections subject to FERC jurisdiction, whereas Connecticut's interconnection guidelines apply to state-jurisdiction interconnections, which typically occur at the distribution level. FERC standards were implemented by ISO-New England (ISO) in ISO Schedule 23, which is applicable to FERC-jurisdictional interconnections.