Short answer: There is no 25% Illinois state income-tax credit for residential solar. It does not exist on the IL-1040, it is not listed in the Illinois Department of Revenue’s schedule of available credits, and DSIRE’s Illinois page does not reference it. If a quote cited a 25% state credit, it was either confused, conflating multiple incentives, or pulling a number out of an affiliate-marketing template. The page below explains what the claim usually conflates and what the real Illinois incentive structure actually looks like.
What people usually mean by “25%”
The number gets used loosely, often to refer to one of three things, none of which is an Illinois income-tax credit.
- Confusion with the (now-expired) federal credit. The federal Residential Clean Energy Credit under Section 25D was a 30% federal credit, not 25%, and it ended December 31, 2025 under Public Law 119-21. The number was wrong even before the credit expired, and the credit it referenced was federal, not Illinois state. Summit’s page on the 2026 federal credit explains the expiration in detail.
- Marketing math that adds incentives together. Some sales decks add the (former) federal credit to the expected Illinois Shines REC payment and the ComEd Smart Inverter Rebate, then express the combined number as a single “total incentive percentage.” That is a sales construct, not a tax-form line item. A homeowner cannot file for a 25% Illinois credit on the IL-1040 because no such credit exists.
- Confusion with a different state’s policy. New York offers a residential solar income-tax credit at the state level (a capped 25% credit under Section 606 of the NY Tax Law). It applies to New York residents installing on a New York property; it does not apply in Illinois. Sales templates written for a national audience sometimes lift the New York figure and apply it generically.
The real Illinois incentive structure
Illinois delivers solar incentives to homeowners through Illinois Shines, the Adjustable Block Program , which compensates homeowners for the Solar Renewable Energy Credits (SRECs) their system produces over a 15-year contract. This is a separate mechanism from an income-tax credit. The payments flow from a state-administered procurement to an Approved Vendor (typically the installer), and the structure of how that value reaches the homeowner, as an up-front purchase price reduction or as periodic payments, depends on the Approved Vendor’s contract terms.
Illinois also exempts solar systems from property-tax reassessment under 35 ILCS 200/10-605 : an installed system does not increase the assessed value of the home for property-tax purposes. That is a real benefit, but it is not an income-tax credit and it is not 25%.
ComEd offers a Smart Inverter Rebate to qualifying residential systems with the right inverter equipment. The rebate amount changes with each ICC tariff cycle; the current value should be verified against ComEd’s filed schedule before treating it as a fixed input on a quote.
Why this myth matters
If an installer’s payback estimate assumes a 25% state credit that does not exist, the homeowner’s real payback is years longer than what the pitch deck showed. The math compounds: the “25% state credit” phantom shaving roughly $5,000 off a $20,000 system, paired with the (now expired) 30% federal credit shaving another $6,000, would have represented well over half the install price as “covered by incentives.” Removing the phantom credit changes the after-incentive net cost by thousands of dollars and shifts the payback range materially.
Common practice in residential solar sales is to lead with the post- incentive net number, not the gross price. Asking for the gross install price first, then the per-line-item incentive math, surfaces this kind of number quickly. Summit’s guide to reading a solar quote walks through the order in which to read the document.
How to verify yourself
- Check DSIRE for Illinois residential solar. The DSIRE database is the federally funded clearinghouse for state-level energy incentives. If a 25% Illinois state credit existed, it would be listed. It is not.
- Read the IL-1040 instructions. The Illinois individual income tax form has a Credits section. There is no residential solar credit line. The Schedule 1299-C, where Illinois non-refundable credits appear, does not include one either.
- Ask the quoting installer to cite the statute. “Section number, please. I want to read it before signing.” A real credit lives in the Illinois Compiled Statutes; a phantom one does not. The installer’s inability or unwillingness to cite the statute is the answer.