Washington State has adopted NEC 2023 as an early adopter, making it one of the more advanced states from a code compliance perspective. The solar market is dominated by Puget Sound Energy and Seattle City Light in the western half, with public utility districts (PUDs) serving most of eastern Washington.
Washington State Solar Snapshot
NEC Edition: 2023 (early adopter) | Primary Utilities: Puget Sound Energy (PSE), Seattle City Light (SCL), multiple PUDs | Net Metering: Mandatory for all utilities under RCW 80.60 | State Incentive: Sales tax exemption on solar | Federal ITC: 30% residential / up to 50% commercial
SurgePV’s solar design suite helps automate compliance documentation.
NEC 2023 in Washington State
Washington adopted NEC 2023 as an early adopter state. Key differences from NEC 2020 that affect WA solar design:
NEC 2023 Changes Relevant to Washington Solar
| Section | NEC 2020 | NEC 2023 (Washington) |
|---|---|---|
| 690.12 Rapid shutdown | 30V/30-sec within array boundary | PVHCS alternative path added |
| Grounding electrode | DC GE for grounded systems >250V | Reorganized, clearer language |
| 706 Energy storage | Article 706 | Updated battery provisions |
| DC arc fault | AFCI for some circuits | Expanded scope |
PVHCS — The New NEC 2023 Alternative
NEC 2023 introduced the Photovoltaic Hazard Control System (PVHCS) as an alternative compliance path for rapid shutdown. A PVHCS can use means other than the specific 30V/30-second measurement to address the firefighter safety concern that 690.12 is designed for.
In practice for Washington installations:
- Most AHJs still accept the standard MLPE/RSD approach from NEC 2020
- PVHCS interpretation varies — confirm with the specific AHJ before specifying a non-standard approach
- Seattle City Light has issued guidance on PVHCS — check SCL’s current technical bulletins
Washington Net Metering — RCW 80.60
Washington’s net metering law is broader than most states — it applies to all utility types:
| Utility Type | Net Metering Required? |
|---|---|
| Investor-owned utilities (PSE) | Yes |
| Municipal utilities (SCL) | Yes |
| Public Utility Districts (PUDs) | Yes |
| Electric cooperatives | Yes |
| Parameter | Details |
|---|---|
| Eligible size | Residential: up to 100 kW; Commercial: up to 1 MW |
| Credit rate | Full retail rate |
| Annual true-up | April 30 — unused credits forfeited (not paid out) |
| Meter | Bidirectional (utility-provided) |
Annual excess: Washington’s net metering credits reset to zero on April 30. Unlike some states that pay out annual excess at an avoided cost rate, Washington forfeits unused credits. Right-sizing the system to not significantly overproduce is more important in Washington than in states with annual excess compensation.
Puget Sound Energy Interconnection
PSE serves the greater Puget Sound region (Bellevue, Kirkland, Redmond, Bothell, Tacoma, Bellingham, Olympia):
| System Size | Process | Timeline |
|---|---|---|
| Under 30 kW residential | Fast Track | 15–30 business days |
| 30 kW–2 MW | Level 1 study | 45–90 days |
| Over 2 MW | Level 2 study | 6–18 months |
PSE documents required:
- One-line electrical diagram
- Site plan with module layout
- Equipment specifications (inverter, modules)
- Washington UTC Rule 10 compliance certification
Seattle City Light Interconnection
Seattle City Light is a municipal utility with its own interconnection process, separate from PSE and state UTC regulations:
| Aspect | Details |
|---|---|
| Application | Submitted to SDCI (Seattle Department of Construction & Inspections) |
| Equipment list | Must use SCL Approved Equipment List |
| Permit integration | Permit and interconnection reviewed together at city level |
| Inspection | Required before SCL activates net metering |
Seattle City Light Approved Equipment List: SCL maintains an approved inverter and equipment list. Verify that all specified equipment is on the current SCL list before finalizing the system design — using unapproved equipment can delay interconnection significantly.
PUD Territory in Washington
Eastern Washington (east of the Cascades) is largely served by Public Utility Districts: Snohomish County PUD, Clark County PUD, Chelan County PUD, Grant County PUD, and others. Each PUD has its own interconnection application, net metering policy, and AHJ requirements. The process differs significantly from PSE and SCL — always contact the specific PUD before starting a project in PUD territory.
Washington Solar Incentives
Sales Tax Exemption
Washington’s B&O tax exemption for solar is one of the cleanest state incentives:
- Sales tax exemption on solar equipment and installation labor
- WA state sales tax is 6.5% (plus local — typically 8–10.5% total)
- Exemption applies to equipment purchase and installation services
- Available through the supplier/installer at time of sale (no application needed)
- This exemption has been renewed multiple times; verify current status at the time of installation
No State Income Tax
Washington has no state income tax, so there is no state solar tax credit.
Federal ITC
| System Type | Base Credit | With Bonuses |
|---|---|---|
| Residential (Section 25D) | 30% | Not applicable |
| Commercial (Section 48E) | 30% | Up to 50% |
Commercial projects in designated energy communities (former Centralia coal plant area in Lewis County may qualify) can add the +10% energy community bonus.
Seattle Building Permit Process
Seattle (SDCI) integrates building permits and solar interconnection review:
- Submit application through the SDCI permit portal
- Structural and electrical review (combined or separate based on system size)
- For residential solar under 15 kW: SolarAPP+ may be accepted — confirm with SDCI
- Plan review: 5–20 business days (varies with SDCI workload)
- Over-the-counter review available for simple residential systems at some Seattle offices
- After permit issuance: complete installation
- Schedule inspections through SDCI
- After inspection approval: submit to SCL for net meter activation
Seattle Environmental Review
Seattle historically designated structures may require additional review before installing visible solar arrays. Check with SDCI and the Seattle Landmarks Preservation Board if the project is on a designated historic structure or in a historic district. This can add weeks to the approval timeline and may restrict panel placement to non-visible roof surfaces.
Design to NEC 2023 for Washington State Projects
SurgePV selects NEC 2023 automatically for Washington State projects and generates permit packages formatted for PSE and Seattle City Light interconnection requirements.
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Frequently Asked Questions
What NEC edition does Washington State use?
NEC 2023 — Washington is an early adopter. Key difference from NEC 2020: PVHCS (Photovoltaic Hazard Control System) is now an alternative compliance path for rapid shutdown. Always confirm with the local AHJ whether they have locally adopted NEC 2023 or still use NEC 2020.
How does Washington net metering work?
RCW 80.60 mandates net metering for all utility types — investor-owned, municipal, PUDs, and cooperatives. Credits accumulate at the full retail rate throughout the year. On April 30, unused credits are forfeited (not paid out). Right-size the system to avoid large annual credit forfeiture.
What solar sales tax exemption does Washington offer?
Washington provides a sales tax exemption on solar equipment and installation labor. WA state sales tax (6.5% + local charges, typically 8–10.5% total) is waived at the point of sale for qualifying solar purchases. No application required — exemption is taken by the seller at time of sale.
