Solar Panel Calculator for Washington (WA)

Q: How many solar panels do I need in Washington?

With 3.4 peak sun hours per day and 400W panels, a typical Washington home using 8070 kWh/month needs approximately 248 panels (99.20 kW system). This accounts for an 80% system efficiency derate factor per industry standards.

Q: How much does solar cost in Washington?

The average solar installation cost in Washington is approximately $2.95 per watt before incentives. A 99.20 kW system costs about $292,640 before the 30% federal ITC, bringing the net cost to approximately $204,848.

Q: What is the solar payback period in Washington?

Based on electricity rates of $0.114/kWh and 3.4 peak sun hours, a typical solar system in Washington pays for itself in approximately 18.2 years. Over 25 years, estimated net savings is $75,836.

Q: Does Washington have net metering?

Washington net metering status: Yes. Contact your local utility for the most current export rates and program details.

Q: What solar incentives are available in Washington?

Solar incentives in Washington include: Federal ITC (30%), sales tax exemption. Always verify current incentive availability with your installer and the DSIRE database.

Q: What wire size do I need for solar panels in Washington?

Solar panel wiring must comply with NEC Article 690. Common sizes include 10 AWG for panel-to-combiner runs (up to 30A), 6 AWG for main DC runs, and appropriately sized AC wiring from inverter to panel. Use our Wire Size Calculator for exact sizing.

Calculate how many solar panels you need in Washington, estimated costs after the 30% federal tax credit, payback period, and 25-year savings. Based on 3.4 peak sun hours/day and $0.114/kWh average electricity rate.

Peak Sun Hours

3.4 hrs/day

Avg Rate

$0.114/kWh

Net Metering

Yes

Solar Rank

#41/51

☀️ Washington Solar Panel Calculator

Monthly Electricity Usage8,070 kWh

Panel Wattage400W

Desired Offset100%

Your Washington Solar System

Panels Needed

248

System Size

99.20 kW

Annual Production

98,486 kWh

Gross Cost

$292,640

Federal ITC (30%)

-$87,792

Net Cost

$204,848

Annual Savings

$11,227/yr

Payback Period

18.2 years

25-Year Savings

$75,836

CO₂ Offset

13.8 tons/yr

Trees Equivalent

230/yr

⚠️ 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	$13,216	$724	18.3 yrs
750 kWh	23	9.2	$18,998	$1,041	18.2 yrs
1,000 kWh	31	12.4	$25,606	$1,403	18.3 yrs
1,250 kWh	39	15.6	$32,214	$1,766	18.2 yrs
1,500 kWh	46	18.4	$37,996	$2,082	18.2 yrs
2,000 kWh	62	24.8	$51,212	$2,807	18.2 yrs
2,500 kWh	77	30.8	$63,602	$3,486	18.2 yrs

Based on 3.4 peak sun hours/day, $0.114/kWh, $2.95/W install cost, 80% derate. 30% federal ITC applied.

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 gross, or $16,520 after the 30% federal ITC. 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

How many solar panels do I need in Washington?

How much does solar cost in Washington?

What is the solar payback period in Washington?

Does Washington have net metering?

What solar incentives are available in Washington?

What wire size do I need for solar panels in Washington?

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