A $100/month electricity bill in Washington represents roughly 926 kWh per month at the state average rate of 10.8¢/kWh (EIA). With 4.0 peak sun hours per day, most Washington homeowners need a 9.3 kW solar system — about 24 panels at 400W — to offset that usage. After the 30% federal ITC, net installed cost runs about $19,500, with 18.7-year simple payback and $24,300+ in estimated 25-year savings.
How Many Solar Panels for a $100 Electric Bill in Washington?
Washington electricity rates and sun hours change the math versus the US average. The sizing formula:
System size (kW) = Annual kWh ÷ (Peak sun hours × 365 × 0.82)
For a $100/month bill in Washington:
Annual usage: ~11,111 kWh/year
Peak sun hours: 4.0 h/day (Washington)
System size:9.3 kW DC (~24 × 400W panels)
Metric
Washington
US average
Rate
10.8¢/kWh
16.3¢/kWh
Sun hours
4.0 h/day
4.5 h/day
System size
9.3 kW
5.5 kW
Panels (400W)
24
14
Washington requires a larger system than the national average for the same dollar bill because higher consumption at lower rates. Use our solar system size calculator with your ZIP code for a roof-specific result.
Find your exact solar savings
Enter your ZIP code for a personalized estimate using your state's electricity rate and sun hours.
💰 System Cost
What Does Solar Cost for a $100/Month Bill in Washington After the ITC?
At $3.00/W installed (SEIA 2026 US average), a 9.3 kW system in Washington costs about $27,800 before incentives.
The 30% Residential Clean Energy Credit (ITC) under IRC Section 25D saves roughly $8,340, bringing net cost to $19,500. The credit applies to purchased systems placed in service through 2032; consult a CPA for your tax situation.
Cost line
Amount
Gross installed (9.3 kW)
$27,800
Federal ITC (30%)
−$8,340
Net cost after ITC
$19,500
📈 Payback Period
How Long Is Solar Payback on a $100 Bill in Washington?
Simple payback divides net system cost by first-year bill savings. In Washington, a 9.3 kW system saving ~$1,044/year against a $100/month bill pays back in about 18.7 years after the ITC.
At 3% annual rate escalation (EIA historical average), 25-year utility spend totals ~$43,800 vs $19,500 net solar cost — an estimated $24,300+ lifetime advantage. Model your timeline in our solar payback calculator.
Solar vs utility company · 25-year comparison
Total cost of staying on the grid vs owning solar for a $300/month bill (national average assumptions).
Washington Solar Incentives for a $100/Month Electric Bill
Washington State exempts solar energy systems from the state sales tax, saving homeowners the 6.5% state sales tax on equipment purchases. Puget Sound Energy and other utilities offer net metering at the full retail rate. Washington’s low electricity rates from hydropower reduce savings potential, but the sales tax exemption provides immediate upfront savings.
Check DSIRE and our Washington solar page for current rebates, net metering rules, and utility-specific programs before signing an install contract.
⚡ System Size
Washington vs US Average: $100/Month Bill Comparison
At Washington's average rate of 10.8¢/kWh and 4.0 peak sun hours, a $100/month bill (~11,111 kWh/year) typically requires a 9.3 kW system — about 24 panels at 400W each. Use our solar system size calculator with your ZIP for a roof-specific estimate.
A 9.3 kW system in Washington costs roughly $27,800 installed before incentives. The 30% federal ITC reduces net cost to about $19,500. Washington State exempts solar energy systems from the state sales tax, saving homeowners the 6.5% state sales tax on equipment purchases. Puget Sound Energy and other utilities offer net metering at the full retail r...
At $19,500 net cost and ~$1,044/year in bill savings, simple payback in Washington is about 18.7 years. High-rate states pay back faster; low-rate states may take longer even with strong sun.
Most Washington homeowners with a $100/month bill see positive 25-year returns — estimated $24,300+ vs staying on utility power with 3% annual rate escalation. See the [Washington solar data page](/states/wa/) for local NEM and incentive details.
The US average needs a 5.5 kW system at 11.0-year payback. Washington needs 9.3 kW with 18.7-year payback — driven by Washington's 10.8¢/kWh rate and 4.0 daily sun hours.