There is no federal tax credit for replacement windows installed in 2026. The Energy Efficient Home Improvement Credit under Section 25C — the one that paid up to $600 on ENERGY STAR Most Efficient windows — ended for property placed in service after December 31, 2025. The St. Louis utilities do not rebate windows. Residential PACE financing in Missouri is suspended. What is left is income-qualified weatherization assistance, which rarely funds windows. If a quote you are holding in 2026 still carries a "tax credit" line or a "qualifies for federal credit" sticker, the rest of the quote deserves a second look.
What happened to the federal credit?
Public Law 119-21, signed July 4, 2025, cut the 25C credit off at the end of 2025. The IRS states on its own FAQ page for the law that "the credit will not be allowed for any property placed in service after December 31, 2025," and its 25C page describes the credit as applying to property placed in service from January 1, 2023 through December 31, 2025. For windows and skylights the credit had been 30% of cost up to $600 per year, and only for products meeting ENERGY STAR Most Efficient. There is no IRS guidance treating a contract signed in 2025 but installed in 2026 as qualifying; the test is placed in service.
ENERGY STAR Most Efficient still exists as a product tier. It no longer unlocks a credit.
Do the utilities rebate windows?
| Utility | What the residential program rebates (latest published) | Windows? |
|---|---|---|
| Ameren Missouri | 2025 PAYS incentive chart: central AC $1,000, air-source heat pump $2,000, ground-source $5,000, mini-split $500/ton, smart thermostat $250, air sealing $0.06/sq ft, attic insulation $0.20/sq ft, duct sealing 50% to $250. No 2026 chart published at this update. | No |
| Ameren Illinois | Smart thermostats, heat-pump water heaters, heat pumps, free Home Energy Assessment with low- or no-cost upgrades for eligible single-family owners. "Weatherization items" in the online marketplace. | No |
| Spire (gas) | Smart thermostat $75, programmable $25, 96%+ furnace $300, boiler $300, water heaters $200–$350, attic insulation R-38+ $0.40/sq ft to $750. Same program categories apply to Spire's eastern (St. Louis) territory per its PSC filing. | No |
Air sealing and attic insulation are rebated and are, per dollar, often a better energy buy than windows. We say so because it is true, not because it sells windows.
Income-qualified weatherization
- Missouri (MoDNR Low-Income Weatherization Assistance): federal DOE funds distributed through eighteen local agencies; an energy audit decides the measures. Windows are not listed among typical measures and are funded only when the audit's cost-effectiveness test supports them, which is uncommon.
- Illinois (IHWAP, through DCEO and local Community Action Agencies): household income at or below 200% of the federal poverty level (for program year 2027, $31,920 for one person, $66,000 for four); measures are air sealing, insulation, HVAC, water heating and health-and-safety items, up to $20,000 per home in energy measures. Windows are not on the measure list.
If you qualify, apply — but plan on the program paying for insulation and a furnace, not windows.
PACE financing
The Missouri Clean Energy District, the one PACE district the state lists as residential-eligible, posts "RESIDENTIAL PROGRAM SUSPENDED" on its site (updated November 18, 2025); commercial PACE continues. Set the PACE St. Louis, the City's program, is listed by the state as commercial, multifamily, nonprofit and public. Missouri's 2021 PACE reform law added Division of Finance oversight, disclosures and valuation rules for residential PACE; the practical effect today is that residential PACE for windows is not available in the St. Louis region.
So what does make windows cheaper in 2026?
- Specifying the right zone product. St. Louis is ENERGY STAR North-Central (U ≤ 0.25, SHGC ≤ 0.40) by EPA's map. An over-specified Northern-zone triple-pane package costs more and performs no better in July. See performance ratings.
- Choosing full-frame only where the frame needs it. See insert vs. full-frame.
- Buying without the in-home sales markup. Every St. Louis competitor we checked in October 2026 prices only at an in-home appointment; the promotions that come with it are built into the number. Our ranges are published. See the cost guide.
- Financing at a real rate. Published St. Louis promotions in October 2026 ran from 6.99% for 60 months to deferred-interest plans at 17.99%, 28.99% and 29.49% APR. A home-equity line or a credit-union loan is usually cheaper than a deferred-interest window plan that is not paid off inside the promotional window. See comparing quotes.
Frequently asked questions
I signed a contract in December 2025 and the windows were installed in February 2026. Can I claim the credit? The IRS test is placed in service. Installed in 2026 means no 25C credit. Talk to a tax professional about your own facts; we are not one.
Is there a Missouri state tax credit for windows? Not for ordinary residential replacement windows. Missouri's historic preservation tax credit is for certified rehabilitation of eligible historic buildings and comes with its own standards; it is a project-level program, not a window rebate.
Does ENERGY STAR Most Efficient still mean anything? As a performance tier, yes — it is a tighter spec than the base ENERGY STAR level. It no longer has a tax consequence.
Will the credit come back? We do not know, and neither does anyone selling you a window today.
Next step
Energy-efficient windows specifies the right glass for this climate without the credit pitch. Related: the cost guide · the complete St. Louis guide.