King County, WA Solar Energy: Panel Permits (2026)

Solar photovoltaic (PV) installations in unincorporated King County require a permit under KCC Title 16 (Building Code) and electrical permits under the Washington State Electrical Code. King County offers streamlined online permitting for residential rooftop solar through MyBuildingPermit.com, Washington's shared online permit system. Typical residential rooftop systems under 25 kilowatts qualify for express review and can be permitted within days. Required submittals include: site plan showing array location, structural verification (either a prescriptive path for standard framing or engineered calculations for larger arrays), electrical single-line diagram showing panels, inverters, disconnects, and point of interconnection, and utility interconnection agreement. Ground-mounted solar arrays require building permits and must meet setback and critical area rules. Puget Sound Energy, Seattle City Light, and Snohomish PUD (depending on service area) handle interconnection and net metering. Washington's net metering statute (RCW 80.60) requires utilities with more than 25,000 customers to offer net metering up to 100 kW residential and 500 kW commercial. Excess generation is credited to the customer's bill. Washington has solar-friendly incentives including the Renewable Energy Production Incentive (sunset 2020, legacy participants continue), federal Investment Tax Credit (30 percent through 2032), and sales tax exemption for solar equipment under 100 kW (RCW 82.08.962). HOA covenants cannot prohibit solar installations (RCW 64.38.055 and RCW 64.90.510). Critical area and shoreline restrictions apply to ground-mounted systems. Tree removal for solar access may trigger clearing permits.