Solar Panel Calculator for Washington (WA)
Calculate how many solar panels you need in Washington, installed cost, payback period, and 25-year savings — updated for 2026 (the 30% federal tax credit expired December 31, 2025). Based on 3.4 peak sun hours/day and $0.114/kWh average electricity rate.
☀️ Washington Solar Panel Calculator
Your Washington Solar System
⚠️ Estimates only. Actual costs and production vary. Consult a licensed solar installer. NEC Article 690 compliance required.
Solar System Sizes by Usage in Washington
| Monthly kWh | Panels | System kW | Net Cost | Savings/yr | Payback |
|---|---|---|---|---|---|
| 500 kWh | 16 | 6.4 | $18,880 | $724 | 26.1 yrs |
| 750 kWh | 23 | 9.2 | $27,140 | $1,041 | 26.1 yrs |
| 1,000 kWh | 31 | 12.4 | $36,580 | $1,403 | 26.1 yrs |
| 1,250 kWh | 39 | 15.6 | $46,020 | $1,766 | 26.1 yrs |
| 1,500 kWh | 46 | 18.4 | $54,280 | $2,082 | 26.1 yrs |
| 2,000 kWh | 62 | 24.8 | $73,160 | $2,807 | 26.1 yrs |
| 2,500 kWh | 77 | 30.8 | $90,860 | $3,486 | 26.1 yrs |
Based on 3.4 peak sun hours/day, $0.114/kWh, $2.95/W install cost, 80% derate. No federal credit applied (25D expired Dec 31, 2025).
Complete Guide to Solar Panels in Washington (2026)
Washington receives an average of 3.4 peak sun hours per day, where high electricity rates can offset moderate sun hours. With average residential electricity rates of $0.114/kWh, solar offers long-term savings potential.
Solar Installation Costs in Washington
The average cost to install solar panels in Washington is $2.95 per watt before incentives. For a typical 8 kW system, that translates to approximately $23,600 installed. The 30% federal ITC expired for systems installed after December 31, 2025, so state and utility programs are now the main cost reducers. Available incentives: Federal ITC (30%), sales tax exemption.
Net Metering in Washington
Washington net metering status: Yes. Washington offers a sales tax exemption on solar equipment and strong net metering.
NEC Requirements for Solar in Washington
All solar installations must comply with NEC Article 690, Solar PV Systems. Key requirements:
NEC 690.8, Circuit Sizing: PV conductors must carry at least 125% of maximum circuit current. For a 10A string, conductors must be rated for 12.5A minimum.
NEC 690.12, Rapid Shutdown: Module-level shutdown must reduce voltage to 80V or less within 30 seconds. Critical for firefighter safety.
NEC 690.31, Wiring Methods: USE-2 or PV Wire within the array; approved wiring methods (EMT, rigid conduit, MC cable) for building penetrations.
NEC 310.15, Ampacity Derating: Conductors in conduit must be derated per Table 310.15(B)(3)(a). Account for seasonal temperature variations when sizing conductors. Use our Wire Size Calculator and Derating Calculator for proper sizing.
Solar Wire Sizing for Washington
Panel strings to combiner box: Typically 10 AWG USE-2 or PV Wire for runs up to 100 feet. Use our Solar Wire Size Calculator to verify.
DC main run to inverter: Usually 6 AWG or 4 AWG THWN-2 in conduit. Keep DC voltage drop under 1.5% with our Voltage Drop Calculator.
AC from inverter to panel: A 7.6kW inverter on 240V draws ~32A, requiring a 40A breaker and 8 AWG copper minimum. Verify with our Breaker Size Calculator.
Environmental Impact
A 99.20 kW system in Washington offsets approximately 13.8 metric tons of CO₂ per year, equivalent to planting 230 trees annually. Washington grid carbon intensity: 0.14 lbs CO₂/kWh.
Disclaimer: Estimates only. Actual costs and production vary by roof orientation, shading, installer, and equipment. Consult a licensed solar installer in Washington. NEC Article 690 compliance required for all installations.
Frequently Asked Questions
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Get Free Solar Quotes →Top 10 Solar States Comparison
| Rank | State | Sun Hours | Rate | Cost/Watt |
|---|---|---|---|---|
| #1 | California | 5.8 | $0.267 | $2.82 |
| #2 | Hawaii | 5.2 | $0.387 | $3.35 |
| #2 | Texas | 5.3 | $0.134 | $2.6 |
| #3 | Arizona | 6.5 | $0.134 | $2.55 |
| #4 | Florida | 5.5 | $0.145 | $2.6 |
| #5 | Nevada | 6.2 | $0.127 | $2.55 |
| #6 | Massachusetts | 3.8 | $0.268 | $3.2 |
| #7 | New Jersey | 4.2 | $0.175 | $2.9 |
| #8 | New Mexico | 6.2 | $0.137 | $2.75 |
| #9 | Colorado | 5.5 | $0.148 | $2.9 |
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Solar Calculator by State
See also: Electricity Cost in Washington