Interconnection Standards (Washington)

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Last modified on February 12, 2015.

Rules Regulations Policies Program

Place Washington

Name Interconnection Standards
Incentive Type Interconnection
Applicable Sector Agricultural, Commercial, Fed. Government, Industrial, Institutional, Local Government, Nonprofit, Residential, Schools, State Government
Eligible Technologies Anaerobic Digestion, Biomass, CHP/Cogeneration, Fuel Cells, Geothermal Electric, Hydroelectric, Landfill Gas, Microturbines, Municipal Solid Waste, Other Distributed Generation Technologies, Photovoltaics, Small Hydroelectric, Small Wind, Solar Thermal Electric, Tidal Energy, Wave Energy, Wind
Active Incentive Yes

Implementing Sector State/Territory
Energy Category Renewable Energy Incentive Programs

Applicable Utilities Investor-owned utilities

External Disconnect Switch Generally required for systems up to 300 kW; not addressed for larger systems

Insurance Requirements "Additional" liability insurance generally not required for net-metered systems. For other systems, requirements vary by system application and/or size; levels established by UTC.

Net Metering Required No

Standard Agreement Yes

System Capacity Limit 20 MW

Date added to DSIRE 2002-07-16
Last DSIRE Review 2012-11-06

References DSIRE[1]


In September 2007, the Washington Utilities and Transportation Commission (UTC) adopted interconnection standards for distributed generation (DG) systems up to 20 megawatts (MW) in capacity. The revised standards provide for two separate levels of interconnection based on system capacity. The first level applies to systems up to 300 kilowatts (kW). The second level, which applies to systems sized between 300 kW and 20 MW, embraces 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.

All interconnections of systems up to 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 up to 300 kW. A UL-approved safety disconnect switch is generally required. However, this requirement may be waived if a customer (1) demonstrates, to the satisfaction of utility, that a system will perform physical disconnection of the generating equipment supply internally, and (2) agrees that service may be disconnected entirely if the system must be physically disconnected for any reason. 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 not greater than 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 greater than 25 kW but not greater than 300 kW. The UTC's rules include provisions for dispute resolution.

For systems sized 300 kW to 20 MW, utilities must offer service equivalent in all procedural and technical respects to the interconnection service the utility offers under the small generator interconnection provisions of its open access transmission tariff (OATT) as approved by the FERC. The FERC's standards 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.

* In general, the FERC's interconnection standards for DG systems up to 20 MW apply to facilities that connect at the transmission level. State-level interconnection standards generally govern interconnection at the distribution level.

Incentive Contact

Contact Name Steve Johnson
Department Washington Utilities and Transportation Commission

Address 1300 South Evergreen Park Drive, S.W.
Address 2 P.O. Box 47250
Place Olympia, Washington
Zip/Postal Code 98504-7250
Phone (360) 664-1346


Authorities (Please contact the if there are any file problems.)

Authority 1: Chapter 480-108 WAC
Date Effective 2006-04-06
Date Enacted 3/6/2006 (subsequently amended)

  • Incentive and policy data are reviewed and approved by the N.C. Solar Center's DSIRE project staff.[1]


  1. 1.0 1.1  "Database of State Incentives for Renewables and Efficiency (DSIRE)"