Data approachEIA rates · NREL sun hours · 2026 federal policy · methodology
A 9 kW solar system in Illinois costs about $27,000 installed in 2026 before incentives and saves roughly $1,490 in year one, a simple payback near 18 years. The 30% federal homeowner credit ended after December 31, 2025, so Illinois Shines is now the main incentive. At an estimated $12,000 in REC value (about $70 per REC), payback falls to roughly 10 years.
Illinois homeowners paid an average of about 18–20¢/kWh for electricity in recent EIA monthly data (19.89¢ in June 2026, up from 18.29¢ a year earlier), compared with a US average of about 18.3¢. Since January 1, 2025, new solar customers of ComEd, Ameren Illinois and MidAmerican are credited for exported power at the supply rate only, which lowers the value of any power you send to the grid. This guide shows every input, keeps Illinois Shines separate so you can plug in your installer’s figure, and links to our full methodology. Statewide numbers are on the Illinois solar page.
💰 System Cost
What Does Solar Cost in Illinois in 2026?
A modeled 9 kW Illinois system costs about $27,000 installed at $3.00 per watt, before Illinois Shines. EnergySage’s marketplace data put the Illinois average at $2.98–$3.02 per watt in August and September 2026, so the model matches current quotes. Its average Illinois quote in that period was an 11.5–12.5 kW system costing roughly $34,400–$37,700.
System size
Panels (400 W)
Installed cost at $3.00/W
Federal credit (2026 install)
7 kW
18
$21,000
$0
9 kW (modeled)
22–23
$27,000
$0
11 kW
28
$33,000
$0
Costs exclude batteries, roof work and electrical upgrades. Illinois Shines and utility rebates are shown separately below.
Until December 31, 2025, homeowners could claim 30% of system cost under §25D. The One Big Beautiful Bill Act (Public Law 119-21, signed July 4, 2025) ended the credit for later expenditures. A 2026 quote for a system you own that subtracts a 30% federal credit is out of date. See our federal solar tax credit guide.
Compare quotes in dollars per watt and ask each installer to list the Illinois Shines payment as its own line item. String inverters typically carry 10–12-year warranties, so budget for a replacement during the system’s life.
🏛️ Incentives
Which Illinois Solar Incentives Are Available in 2026?
Illinois Shines is now the main incentive for Illinois homeowners. It makes one upfront payment for the renewable energy credits (RECs) your system is expected to produce over 15 years, and your Approved Vendor usually passes that value to you.
Incentive
Status for a 2026 install
How you receive it
Federal §25D credit (30%)
Ended after Dec 31, 2025
2025 installs only, claimed on the 2025 return
Illinois Shines (Adjustable Block Program)
Available
REC payment through an Approved Vendor
Illinois Solar for All
Available to income-eligible households
Enhanced incentives through approved vendors
Utility rebate (ComEd, Ameren)
Offered for solar and/or batteries with a smart inverter
Upfront rebate; confirm the current amount with your utility
Export credit (new customers)
Supply-only since Jan 1, 2025
Bill credit for exported kWh
Lease / PPA
Provider may still use the commercial §48E credit if it qualifies
Only through a lower lease or PPA price, if passed on
How much is Illinois Shines worth? Value = expected REC volume × price per REC. For systems up to 10 kW, 2026–27 prices reported by Illinois Shines installers run about $70 per REC in Ameren Illinois territory and about $81 in ComEd territory; systems above 10 kW fall into a lower-priced tier. Our 9 kW model produces about 172 RECs over 15 years (11.85 MWh a year, reduced 0.5% annually). That implies roughly $12,000 at $70 and $13,700 at $80. Treat these as estimates, not quotes: REC prices are set by the Illinois Power Agency each program year and your installer’s pricing will differ. Confirm the current price at illinoisshines.com and ask a tax professional how the payment is treated.
Who can still use a federal credit? Homeowners whose systems were completed in 2025 claim 30% on the 2025 return, and unused §25D credit can carry forward. Businesses and farms that own solar may still qualify for §48E under the law’s deadlines. Check DSIRE for utility and local programs. This is not tax advice.
📋 Savings
How Much Will Solar Save on Your Illinois Electric Bill?
A 9 kW system saves about $1,490 in year one. The model assumes solar offsets about 70% of the bill, reflecting supply-only credits for exported power. That 70% is a modeling assumption, not a measured figure.
Input / result
Value
System size
9.0 kW
Peak sun hours (modeling assumption)
4.4 per day
Annual production (kW × sun × 365 × 0.82)
~11,850 kWh
Electricity rate (recent EIA range 18–20¢)
18.0¢/kWh
Bill without solar
$2,130/yr ($178/mo)
Bill offset
0.70
Year-1 savings (11,850 × $0.18 × 0.70)
~$1,490
Installed cost before Illinois Shines
$27,000
Simple payback
~18.1 years
25-year bills without solar (3%/yr increases)
~$77,800
25-year net savings (3%/yr rates, 0.5%/yr degradation, minus cost)
~$23,900
By monthly bill (same assumptions, before Illinois Shines):
Monthly bill
System size
Installed cost
Year-1 savings
Payback
25-yr net savings
$100
5.1 kW
$15,200
~$840
~18 yrs
~$13,500
$150
7.6 kW
$22,800
~$1,260
~18 yrs
~$20,200
$200
10.1 kW
$30,400
~$1,680
~18 yrs
~$26,900
Assumptions: system sized to annual usage at 18¢/kWh and 4.4 sun hours; year-1 savings = bill × 12 × 0.70; $3.00/W; 3% annual rate escalation; 0.5% annual degradation; no Illinois Shines payment.
Winter output in Illinois is low and summer output is high. Shifting flexible loads such as EV charging, laundry and water heating into daylight raises self-consumption above 0.70, and so does a battery. Utility rebates exist for batteries paired with solar and a smart inverter; ask ComEd or Ameren for current terms. Use the solar savings calculator with your own bill.
📈 Payback Period
What Is the Solar Payback Period in Illinois?
About 18 years before incentives in our model. Illinois Shines shortens that: each $1,000 of REC payment cuts simple payback by roughly 0.7 years.
Data visualization
Simple payback by scenario. A 9 kW Illinois system repays its $27,000 cost in about 18.1 years with no incentive and about 10.0 or 8.9 years with an estimated Illinois Shines REC payment. Source: Green Energy Calculators model, EIA 2026 rates, Illinois Power Agency REC prices.
Chart summary: With no incentive, the system takes about 18.1 years to repay its $27,000 cost from bill savings. An estimated Illinois Shines payment of about $12,019 (at ~$70 per REC) cuts that to about 10.0 years, and about $13,736 (at ~$80 per REC) cuts it to about 8.9 years. Actual results depend on your territory, system size and quoted REC payment.
Scenario
Estimated REC payment
Net cost
Simple payback
Break-even with 3% rate growth
25-yr net savings
No Illinois Shines
$0
$27,000
~18.1 yrs
~year 16
~$23,900
~$70 per REC
~$12,019
~$14,981
~10.0 yrs
~year 10
~$35,900
~$80 per REC
~$13,736
~$13,264
~8.9 yrs
~year 9
~$37,600
Data visualization
25-year cumulative net position, 9 kW system. Break-even falls near year 16 with no incentive and years 9 to 10 with Illinois Shines, assuming 3 percent annual rate growth, 0.5 percent degradation and no federal credit. Source: Green Energy Calculators model, EIA 2026 rates.
Chart summary: All three lines start below zero at the net cost and rise as bill savings accumulate and electricity prices grow. Without Illinois Shines the system breaks even in about year 16 and ends year 25 about $23,900 ahead. With an estimated Illinois Shines payment it breaks even around years 9 to 10 and ends about $35,900 to $37,600 ahead. Rate growth shortens break-even compared with the simple-payback figures in the bar chart above.
Financing lengthens payback. Interest adds to the total and some solar loans build a dealer fee into the price, so ask for both the cash price and the financed price. The solar loan calculator and solar ROI calculator show the effect. With a lease or PPA, the provider keeps the REC value, so compare its price per kWh with your own rate using the lease vs. buy calculator.
A 2019 Zillow analysis found homes with solar sold for about 4.1% more on average. The premium varies by market and is not included in our payback figures. For other states, see solar payback by state, or compare neighboring Indiana and Wisconsin.
⚡ System Size
How Do You Choose an Illinois Installer and Size Your System?
Size the system from your last 12 months of usage, then choose a licensed Illinois Shines Approved Vendor that shows the REC payment and export-credit assumptions in writing.
Sizing: Divide annual kWh by about 1,317 (4.4 sun hours × 365 × 0.82). A home using 11,850 kWh a year needs about 9 kW. Sun hours vary across Illinois, so check your address in NREL’s PVWatts. Because exports earn only the supply-rate credit, sizing slightly below 100% of annual usage can improve returns. The solar system size calculator adjusts for tilt and shading.
Vetting installers:
Confirm the company is an Illinois Shines Approved Vendor and ask whether the lead installer holds NABCEP certification.
Get at least three quotes. Compare price per watt before incentives, the REC payment, equipment models and the production estimate.
Reject any 2026 quote for a system you would own that subtracts a 30% federal tax credit.
Look for a workmanship warranty of 10+ years and clear terms for removing and reinstalling panels during roof work.
Walk away from same-day-only pricing and pressure tactics.
Sources: EnergySage Illinois solar cost data (Aug–Sep 2026); EIA Electric Power Monthly residential prices; Illinois Shines and Illinois Power Agency REC price schedules; Illinois Citizens Utility Board and Illinois Shines net-metering notices; IRS guidance on §25D; DSIRE; Zillow (2019). Model details: methodology. Figures are estimates, not quotes or tax advice.
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Not for a system you own. The 30% Residential Clean Energy Credit (§25D) ended for expenditures made after December 31, 2025. If your Illinois system was completed in 2025, claim it on your 2025 return with IRS Form 5695. Leases and PPAs may still pass through part of the commercial §48E credit if the provider qualifies. Illinois Shines is unaffected, so it is now the main incentive for 2026 installs.
About $3.00 per watt installed. EnergySage reported Illinois averages of $2.98 to $3.02 per watt in August and September 2026, so a 9 kW system costs roughly $27,000 and an 11.5 kW system about $34,400, before incentives. No federal credit is subtracted. Illinois Shines payments, which depend on your territory and system size, reduce the net cost.
Illinois Shines, run by the Illinois Power Agency, pays for the renewable energy credits (RECs) your system is expected to generate over 15 years. Homeowners work through an Approved Vendor, usually the installer, who registers the system and passes the payment to you, often as an upfront discount or payment. Prices are set per program year and vary by utility territory and system size, so get the exact figure in writing.
Yes, but it is reduced for new customers. Systems interconnected after December 31, 2024 receive credits for exported power at the supply rate rather than the full retail rate, and the credits do not expire. Power you use as it is produced still avoids the full retail rate. Systems interconnected before 2025 are grandfathered under the previous rules.
In our model, about 18 years before incentives: $27,000 divided by about $1,490 of year-one savings from a 9 kW system at 4.4 sun hours, 18¢/kWh and a 0.70 bill offset. An estimated Illinois Shines payment of $12,000 to $13,700 would cut that to about 9 to 10 years. Your result depends on your rate, usage, shading and the REC payment you are quoted.
$178/month electric bill by state
System size and payback vary by electricity rate and sun hours — see your state.
19.22¢/kWh — Illinois average residential price. Source: EIA Electric Power Monthly, Table 5.6.B (year-to-date through July 2026), residential average retail price (July 2026) (EIA)
Solar production
4.4 peak sun hours/day × 0.82 system derate. Approximate state-average daily solar resource (peak sun hours) based on NREL solar resource data (NSRDB); not location-specific — use NREL PVWatts for an address-level estimate. (NREL PVWatts)
Installed price
$3.00 per watt before incentives. Blended 2026 US residential installed price used by this site; EnergySage marketplace reported about $2.60/W (mid-2026); full-market medians are higher.
Federal tax credit
$0 for homeowner-owned systems installed in 2026 — the 30% §25D credit ended Dec 31, 2025 (IRS)
Net metering
Net billing / reduced export credit — solar assumed to offset 70% of the bill. Since 2025, new Illinois ComEd and Ameren customers receive a supply-only credit for exports rather than full retail.
Estimates only — not tax, legal or financial advice. Get at least three installer quotes and confirm incentives with your utility and a tax professional.