Are Solar Panels Worth It in Illinois?
In Illinois, 5.5 kW of panels costs about $15,950 and pays for itself in 8 years and 6 months, saving roughly $47,592 over 25 years.
The average Illinois home uses 693 kWh of electricity a month and pays $165 for it. Covering 90% of that takes roughly 5.5 kW of panels, which at the Illinois average of $2.90 per watt is about $15,950 installed. Against a bill that drops to around $29 a month, the system breaks even in 8 years and 6 months and leaves about $47,592 in your pocket over a 25-year life.
Two things drive that number more than the panels themselves. Illinois power costs 23.85¢ per kWh, so every kilowatt-hour you generate is worth exactly that much and rises with the utility every year — the model assumes 4% a year. And since the 2026 tax year there is no federal residential tax credit: the 30% credit under Section 25D ended on 31 December 2025, so a cash or loan purchase now carries the full price. The calculator below opens on the Illinois numbers; replace them with your own quote, your own bill, and any rebate your utility still offers.
Solar Panel Payback & ROI Calculator
Estimate upfront costs, monthly utility savings, and the break-even payback period of your solar panel system
Results
Payback Period
— Years
25-Year Utility Savings: $79,247 · Net Upfront Cost: $24,000
Net Lifetime Savings
$55,247
Return on Investment (ROI): 230.2%
Internal Rate of Return (IRR)
10.23%
Annual Savings: $2,040
Monthly Bill Savings
$170
Net Upfront Cost: $24,000
Cumulative Savings vs. Net Upfront Cost
25-Year Amortization Schedule
| Year | Panel Output | Annual Savings | Net Cash Flow |
|---|---|---|---|
| 1 | 100.0% | $2,040 | -$21,960 |
| 2 | 99.5% | $2,111 | -$19,849 |
| 3 | 99.0% | $2,184 | -$17,665 |
| 4 | 98.5% | $2,260 | -$15,404 |
| 5 | 98.0% | $2,339 | -$13,065 |
| 6 | 97.5% | $2,421 | -$10,644 |
| 7 | 97.0% | $2,505 | -$8,140 |
| 8 | 96.6% | $2,592 | -$5,548 |
| 9 | 96.1% | $2,682 | -$2,866 |
| 10 | 95.6% | $2,775 | -$90 |
| 11 | 95.1% | $2,872 | +$2,782 |
| 12 | 94.6% | $2,972 | +$5,754 |
| 13 | 94.2% | $3,075 | +$8,829 |
| 14 | 93.7% | $3,182 | +$12,012 |
| 15 | 93.2% | $3,293 | +$15,305 |
| 16 | 92.8% | $3,408 | +$18,713 |
| 17 | 92.3% | $3,526 | +$22,239 |
| 18 | 91.8% | $3,649 | +$25,888 |
| 19 | 91.4% | $3,776 | +$29,665 |
| 20 | 90.9% | $3,908 | +$33,572 |
| 21 | 90.5% | $4,044 | +$37,616 |
| 22 | 90.0% | $4,184 | +$41,800 |
| 23 | 89.6% | $4,330 | +$46,130 |
| 24 | 89.1% | $4,481 | +$50,610 |
| 25 | 88.7% | $4,636 | +$55,247 |
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Payback in Illinois by what you pay per watt
Same 5.5 kW system and the same $165 bill — only the installer quote changes. No federal credit, no state rebate, 4% annual utility inflation.
| Quoted price per watt | System cost | Payback | Net 25-year saving |
|---|---|---|---|
| $2.50 | $13,750 | 7 years and 6 months | $49,792 |
| $2.70 | $14,850 | 8 years | $48,692 |
| $2.90 | $15,950 | 8 years and 6 months | $47,592 |
| $3.10 | $17,050 | 9 years and 1 month | $46,492 |
| $3.30 | $18,150 | 9 years and 6 months | $45,392 |
Frequently Asked Questions
- About 8 years and 6 months for a typical 5.5 kW system bought at the Illinois average of $2.90 per watt. That assumes the system covers 90% of a $165 monthly bill and that power prices keep rising around 4% a year. A cheaper quote or a higher bill shortens it; a shaded roof or a cash-out at a low utility rate lengthens it.
- Around $2.90 per watt installed, so roughly $15,950 for the 5.5 kW system an average Illinois home needs. Price per watt falls as the system grows — the fixed costs of permits, inverter and labour spread over more panels — which is why small systems rarely quote at the state average.
- Not for a system you buy. The residential clean energy credit (Section 25D) was ended by the One Big Beautiful Bill Act for anything installed after 31 December 2025, so a 2026 cash or loan purchase receives nothing federal. Leases and power purchase agreements are different: the company that owns the panels claims the business credit and may price some of it into your rate. State and utility programmes are unaffected — check yours and enter it as a rebate in the calculator.
- On these assumptions, yes — about $47,592 net over 25 years, on top of returning the $15,950 you spent. The reason is the 23.85¢ per kWh Illinois charges: solar is worth whatever the power it replaces would have cost, so the same panels are a far better deal in an expensive state than a cheap one. Selling the house before the break-even point is the main way this goes wrong, though a paid-off system usually lifts the sale price.
- Roof repairs done before installation, an inverter replacement somewhere around year 12–15, and any battery. On the other side it also leaves out state and utility rebates, net-metering credits for power you export, and the property-tax exemption many states give solar equipment. Enter the ones that apply to you — the rebate field takes them directly.
Solar payback by state
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