Short answer: most Illinois homeowners pay roughly $2.60–$3.40 per watt before incentives.
| System size | Typical cost before incentives |
|---|---|
| 6 kW | $15,600–$20,400 |
| 8 kW | $20,800–$27,200 |
| 10 kW | $26,000–$34,000 |
| 12 kW | $31,200–$40,800 |
What Moves the Price
- Roof size, pitch, and condition
- Panel and inverter quality
- Battery storage (adds roughly $10,000–$15,000)
- Ground mount vs rooftop
- Electrical panel upgrades
What Brings It Down
Illinois Shines SREC payments (often several thousand dollars across the contract), your utility’s Distributed Generation rebate, and avoiding over-sized systems. Note the federal credit change: for homeowner-owned systems placed in service in 2026, the old 30% federal credit no longer applies.
The Number That Matters
Cost per watt, after incentives, compared across at least three quotes. Our quote form lines that comparison up for you.