Illinois solar savings calculator
See roughly what size system your home needs, what it costs after Illinois incentives, and how fast it pays for itself.
Quick answer
How much can solar save in Illinois?
For a Chicago-area home with a $150 monthly ComEd bill, we estimate an 8.0 kW system costs about $10,800 after the utility rebate and Illinois Shines, saves about $1,248 in the first year and pays for itself in about 8.7 years. Enter your own bill below.
Your estimate
- System size
- 8.0 kW
- about 20 panels
- Yearly production
- 9,600 kWh
- vs. about 9,529 kWh used
- First-year savings
- $1,248
- about $104/month
- Payback
- 8.7 years
- $42,500 saved over 25 years
| Estimated cost before incentives | $24,800 |
|---|---|
| ComEd solar rebate | −$2,400 |
| Illinois Shines REC valueUsually paid to your installer and passed on as a lower price. | −$11,600 |
| Estimated net cost | $10,800 |
Planning estimate only, not a quote. Assumes a south-facing roof, cash purchase and half of production used at home. Real numbers depend on your roof, equipment, rate plan and current program prices. How we estimate
How does this calculator estimate savings?
We turn your bill into yearly electricity use, size a system to cover it, and price it with October 2026 Illinois incentive values. You can change the electric rate and installed price under "Adjust assumptions".
- Usage: your bill minus about $15 a month in fixed charges, divided by an all-in rate of 17¢/kWh. Illinois residential prices ran roughly 15–20¢ in 2025–26.
- Production: about 1,200 kWh per kW each year in northern Illinois, rising to about 1,330 in far southern Illinois, for an unshaded south-facing roof. "Some shade" lowers that by 15% and "a lot" by 30%.
- System size: enough to cover your yearly use, between 3 and 25 kW, using 400 W panels.
- Price: $3.10 per watt before incentives, minus the $300/kW ComEd or Ameren rebate and the Illinois Shines REC value: 15 years of expected production at the 2026–27 small-system price of about $80.77 per REC in ComEd territory or $70.37 in Ameren territory (systems over 10 kW get somewhat different prices). We leave out the extra Shines payment for customer-owned systems, so the real incentive may be a little higher.
- Savings: half of production used at home at the full rate and half exported at about 9¢/kWh, the supply-rate credit for new systems, capped at the part of your bill solar can offset. Lifetime savings assume rates rise 3% a year and panels lose 0.5% of output a year over 25 years.
Batteries, financing costs, roof work, property tax treatment and changes to Illinois Shines block prices aren't included. Under the 2026 Illinois Shines contract, half of the REC payment is made at energization and the rest over the following six years, which affects how installers price systems.
Sources
- Illinois Shines: Final 2026–27 REC prices for the program year starting June 1, 2026
- Illinois Shines: Small distributed generation
- Citizens Utility Board: Solar and storage rebates (ComEd and Ameren)
- Illinois Shines: FAQs related to changes in net metering in Illinois
- NREL PVWatts Calculator
- U.S. EIA: Average retail price of electricity by state (Electric Power Monthly, Table 5.6.A)
- IRS: FAQs on changes to Sections 25C, 25D and other credits under the 2025 law (Public Law 119-21)
Solar calculator FAQ
How accurate is this solar calculator?
It's a planning estimate. It uses your bill, your area's typical sunshine and current Illinois incentive values, but not your roof's exact pitch, direction or shading, your equipment or your rate plan. An installer's proposal, based on your actual roof and usage, is the number to rely on.
Why does the calculator subtract Illinois Shines from the price?
Illinois Shines buys the renewable energy credits (RECs) your system will produce over 15 years. The payment goes to your installer, who usually lowers your price by about that amount. See Illinois Shines, explained.
Why aren't my savings equal to my whole bill?
Fixed customer and meter charges stay on your bill with solar, and for systems connected since 2025, power you send back to the grid is credited at the supply rate rather than the full price. Power you use as it's produced still saves the full rate. See Illinois net metering.
Does the calculator include the federal solar tax credit?
No. The federal residential clean energy credit ended for homeowner-owned systems after 2025. Leases and PPAs can still pass along a business tax credit as a lower rate. See the federal tax credit in 2026.
What if I lease or sign a PPA instead of buying?
With a lease or PPA you pay little or nothing upfront and pay a monthly or per-kWh price instead, so payback doesn't apply. Your savings are the difference between that price and what you'd otherwise pay your utility. See solar lease vs. buy.