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Washington Interconnection Standards

Date Last Updated8/13/2014
Policy TypeInterconnection Standard
Policy Administrator/Contact OfficeWashington Utilities and Transportation Commission (UTC)
Policy Initiation Date4/6/2006
Policy SummaryThe UTC adopted interconnection standards for distributed generation (DG) including CHP systems up to 20 MW in capacity. The standards provide for two separate levels of interconnection based on system capacity. The first level applies to systems up to 300 kW. The second level, which applies to systems >300 kW but up to 20 MW, is based on the Federal Energy Regulatory Commission's (FERC) interconnection standards. The UTC's standards apply to the state's investor-owned electric utilities -- but not to municipal utilities or electric cooperatives.

Interconnection of systems <300 kW must conform to all applicable codes and standards for safe and reliable operation, including the National Electric Code (NEC); National Electric Safety Code (NESC); the standards of the Institute of Electrical and Electronics Engineers (IEEE); the standards of the North American Electric Reliability Corporation (NERC); the standards of the Western Electricity Coordinating Council (WECC); American National Standards Institute (ANSI); Underwriters Laboratories (UL) standards; local, state and federal building codes, and any electrical company's written electric service requirement approved by the UTC.

With utility approval, interconnection to spot networks and area networks is permitted for systems <300 kW. A UL-approved safety disconnect switch is generally required. However, this requirement may be waived under certain circumstances. Utilities have the authority to review the need for a dedicated distribution transformer. If such equipment is necessary, the customer must pay for the costs. Systems eligible for net-metering do not require additional liability insurance. However, utilities are authorized to require additional insurance and indemnification for systems ineligible for net-metering (but up to 300 kW).

Utilities must have a designated point of contact for customers seeking to interconnect systems up to 300 kW, and must file with the UTC a standard form application and a model interconnection agreement. Application fees are limited to $100 for systems up to 25 kW, and $500 for systems >25 kW up to 300 kW. The UTC's rules include provisions for dispute resolution. For systems sized 300 kW to 20 MW, interconnection procedures are based on FERC standards. The FERC guidelines for systems up to 20 MW provide for three levels of interconnection. However, the first level -- the 10 kW inverter process -- does not apply in Washington, because these smaller systems are covered by the rules described above. The UTC could approve an alternative proposal if a utility demonstrates that the FERC's interconnection standards will impair service adequacy, reliability or safety, or will otherwise be incompatible with the utility's electric system.
CHP Eligibility RequirementsBoth fossil-fueled and renewably-fueled CHP systems are eligible for standardized interconnection.
Eligible Project Size (MW)Standardized interconnection applies to systems up to 20 MW.
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