Illinois vs Washington Solar Comparison
Illinois gets more sun (4.0 hrs/day) while Illinois has the faster payback (9 years).Illinois offers higher 20-year savings at $32,600.
Illinois
4.0 hrs
9yr payback
$32,600
20yr savings
Washington
3.5 hrs
12.5yr payback
$22,800
20yr savings
Side-by-Side Comparison
| Metric | Illinois | Washington |
|---|---|---|
| Peak Sun Hours | 4.0 hrs | 3.5 hrs |
| Cost per Watt | $3.15 | $3.10 |
| 6kW System Cost | $18,900 | $18,600 |
| Federal Tax Credit | 30% | 30% |
| State Tax Credit | None | None |
| State Rebate | None | None |
| Net Metering | Full Net Metering | Full Net Metering |
| Electricity Rate | 16.27¢/kWh | 11.26¢/kWh |
| Payback Period | 9 years | 12.5 years |
| 20-Year Savings | $32,600 | $22,800 |
Verdict
Illinois is the better state for solar ROI with $32,600 in 20-year savings and a 9-year payback period. Illinois has more sun exposure at 4.0 hrs/day, making it ideal for maximum energy production. Both states qualify for the 30% federal solar tax credit.
Frequently Asked Questions
Is solar better in Illinois or Washington?
Illinois gets more sun (4 peak hours/day vs 3.5). Illinois has a faster payback (9 years) and Illinois offers higher 20-year savings ($32,600).
How do solar costs compare between Illinois and Washington?
A 6kW system costs $18,900 in Illinois vs $18,600 in Washington before incentives. Both qualify for the 30% federal tax credit.
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Data verified March 2026 · Source: NREL, DSIRE, EIA