Rules by state

Solar and battery interconnection rules in Washington

Washington interconnection of generating facilities (WAC 480-108). Every threshold below was read out of the document linked at the bottom of this page, and the same rules answer the free screening check.

Who this binds: investor owned utilities. A utility outside that list sets its own terms, so confirm who serves the address first.

Check a Washington address free
How the size is measured

nameplate capacity: the manufacturer output capacity of the generating facility. For a system that uses an inverter to change DC energy supplied to an AC quantity, the nameplate capacity is the manufacturer AC output rating for the inverters, measured in kilowatts. The point of common coupling is the point of measurement.

Size bands and what each one obliges

Tier 1 Size 0 to 25 kW

Inverter based, single phase, 25 kW or less, at secondary voltage, requiring no construction beyond a meter change. No additional insurance is necessary below 100 kW. The application fee is no greater than $100.

  • Application fee no greater than $100
  • Single phase service
  • No utility construction beyond a meter change
  • No insurance
Tier 2 Size 25.001 to 500 kW

Up to 500 kW at or below 38 kV class and not a synchronous generator. The application fee is no greater than $500. No additional insurance is necessary below 100 kW; above that the rule states no amount.

  • Application fee no greater than $500
Tier 3 Size 500.001 to 20000 kW

Anything that does not qualify for the smaller tiers, up to 20 MW. The application fee is no greater than $1,000.

  • Application fee no greater than $1,000

The screens that decide it

Ask the utility this, before you sell it

  1. Is this service single phase or three phase? A three phase system of any size drops out of Tier 1 in Washington on configuration alone, regardless of how small it is.
  2. What is the cumulative net metering capacity on this utility against four percent of its 1996 peak demand? Net metering is first come first served until the earlier of 30 June 2029 or that cap, the denominator is a fixed historical number that does not grow, and the cap is per utility.
  3. Is this address served by a public utility district, municipal or cooperative? Those utilities owe net metering under the statute but none of the tiers, fees or timelines in this chapter apply to them.

Worth knowing before you quote

Washington states plainly that no additional insurance is necessary for a facility with a nameplate capacity under 100 kW, and states no amount above it. Where separate applications are submitted for each phase of a project, a separate application fee is required for each phase. The chapter was last substantively revised in 2013 and contains no definition of energy storage, export capacity, limited export, non export or power control system, so a battery paired quote in Washington is screened against a rule that does not contemplate the equipment. The 30 June 2029 net metering sunset is close enough that a pre sale tool will begin hitting it.

Utility programs we have read in Washington

Source

Washington Administrative Code Chapter 480-108, interconnection with electric generating facilities, and Revised Code of Washington Chapter 80.60 net metering

Read and recorded 2026-09-12. The interconnection chapter binds only electrical companies subject to Commission jurisdiction, which means Puget Sound Energy, Avista and Pacific Power. Seattle City Light, Tacoma Power, the public utility districts and every cooperative are outside it. The net metering statute is the opposite and reaches essentially every distributor including public utility districts, irrigation districts, port districts, cooperatives and municipal utilities.

What to do with this

Check a real address

The rules below are the general case. Run the free check to see which utility serves a specific address, which tier the system lands in, and what to ask.

Run the free check
Installers: keep the answer with the job

GridProjeX holds the project from here, with every value tied to the document it came from and the utility and permit tracks run to permission to operate.

How it works for installers
Utilities: see what applicants are told

The same published rules your applicants read here are the ones your queue sees. GridProjeX is the record both sides work from.

How it works for utilities

Also from CivyxIQ, if they fit what you already do: SolarProjeX for running the crews and the jobs, and Solar Home so the homeowner can follow their own project. Neither is needed to use the checker.