The green cell was still there.
Thirty percent, subtracted neatly from the bottom of a solar proposal, in a spreadsheet opened on a kitchen laptop in . The formula worked. The formatting worked. The little dollar sign had its commas in the right places. Only the law behind the cell had disappeared.
I have an old road atlas with the same problem. A bridge in it crosses a river in western Illinois because the cartographer printed the bridge in blue ink. Drivers using a current map know the crossing has changed. The atlas remains serenely certain. Paper is excellent at preserving instructions and terrible at noticing when the world moves on.
A surprising amount of residential solar math now lives in that atlas.
The Cell That Refused to Die
For years, the federal Residential Clean Energy Credit gave homeowner-owned solar a familiar headline number: 30 percent. It became muscle memory. Sales calculators treated it as the second movement in a two-step dance. First show the gross price; then make nearly a third of it vanish.
The IRS now states the boundary plainly. Qualified residential clean energy property installed from 2022 through could earn the credit. Property placed in service after cannot. For an Illinois homeowner buying a system with cash or a loan and completing the installation in 2026, the federal residential credit is zero.
That fact is easy to read and oddly hard to absorb. Thirty percent had become part of the category, like assuming a house comes with stairs. Take it away and every old comparison article, saved proposal, video calculator, and neighbor's 2024 experience needs to be handled as historical material.
The number may still appear in a polished 2026 presentation. A formula can outlive its authority by years.
A spreadsheet obeys the cell it was told to subtract, even after Congress changes the rule.
December 31 Was a Finish Line
The important verb in the IRS guidance is installed. A deposit made in 2025 did not preserve the homeowner credit for a system finished in 2026. A signed contract did not freeze it. An equipment order sitting in a warehouse did not place the property in service.
This distinction matters because solar transactions have several dates that feel official. There is the signature date, the financing date, the day panels reach the roof, the inspection date, and the day the utility grants permission to operate. Homeowners naturally reach for whichever date protects the number they expected. Tax rules do not rearrange themselves around that expectation.
The old credit can still matter to an old installation
A qualifying system completed by the end of 2025 belongs to a different tax year. The IRS says the credit was nonrefundable, meaning it could reduce tax owed only to the available amount, while unused eligible credit could be carried forward. That is a question for the homeowner's tax records and tax professional, separate from whether a new 2026 purchase earns a credit.
The separation is useful. One folder may contain a valid 2025 claim. The new proposal on the kitchen table still begins at zero federal residential credit.
A Tax Credit Was Never a Store Discount
Even while Section 25D was active, the word credit did considerable work. Some proposals displayed it beside manufacturer promotions and state program value, creating the visual impression of money removed at checkout. The homeowner usually paid the contractor's full price or financed it. The tax result arrived later and depended on the household's return.
That sequencing matters more now because a stale proposal can hide the expired credit in at least two places. It may show up as a line-item reduction in “net system cost.” It may also appear as a planned loan re-amortization, where the monthly payment assumes the homeowner will contribute a tax benefit to the principal by a deadline.
Remove the federal credit and the second payment path can rise sharply. The exact change belongs in the loan documents; a salesperson's monthly-payment slide is too small a container for it.
Here is the practical test I prefer. Cover every incentive line with a sheet of paper. Read the cash price, financed amount, interest terms, and payment schedule that remain. Then uncover each incentive separately and ask who receives it, under which rule, and at what point in the transaction. If the proposal becomes unintelligible when the 30 percent cell is hidden, the proposal was using federal tax policy as structural lumber.
Rebuild the 2026 Price From Zero
A 2026 solar evaluation should begin with the gross installed price and the home's expected production. Those two figures have to stand without federal assistance. From there, Illinois-specific value can be added with its own documentation.
This is slower than pressing “recalculate,” which is exactly why it works. It prevents a dead federal number from being smuggled back under a softer name such as “estimated tax savings” or “anticipated incentive value.” It also makes financing costs visible. Interest and loan origination charges do not become qualified clean energy costs merely because they helped purchase the equipment; the IRS specifically excludes interest, including loan origination fees, from the old credit calculation.
Keep four ledgers, even if the proposal uses one
I would separate the project into gross price, Illinois program value, utility-bill effects, and financing. Each moves on a different clock. The contract sets the price. Illinois Shines follows program rules and a REC contract. Bill savings depend on production, household consumption, and utility crediting. Financing follows the note.
Combining them creates a smooth number. Separation creates a number you can inspect.
The result may still support solar. Illinois electric rates and state programs can make a suitable home worth reviewing. A 2026 project simply has to earn that answer under 2026 rules.
Illinois Did Not Empty the Cupboard
The federal change removed one large plate from the table. Illinois programs remain, with their own eligibility requirements and payment mechanics.
Illinois Shines continues to purchase the renewable energy credits associated with qualifying systems through Approved Vendors. For the program year that began , the Illinois Power Agency's published price sheet lists $80.77 per REC for small distributed-generation projects up to 10 kW AC in Group B, the ComEd territory, and $70.37 in Group A, the Ameren Illinois territory. One REC represents one megawatt-hour of renewable generation.
The same state price sheet created a $20-per-REC adder for qualifying customer-owned small systems that will not receive a federal investment or residential clean energy tax credit. That is a state response to the vanished federal benefit. It does not recreate 30 percent, and it should never be described as if it does.
The sober way to handle these layers is to check the home, the utility, the proposed system, and the dated program terms before hearing a pitch. The Day Company does that screening for ComEd and Ameren Illinois homeowners and places current, source-linked figures ahead of the installation conversation. A home that still works on the new arithmetic deserves a full review. A home that depended on the retired credit deserves an honest stop.
The Lease Door Has Different Hinges
Some 2026 offers will say the “federal incentive” survives through a lease or power purchase agreement. The underlying distinction is ownership. In those arrangements, a commercial entity generally owns the equipment and may pursue business-side tax treatment if the project satisfies the applicable rules. The homeowner does not claim the old Section 25D residential credit.
Every lease still requires its own examination. Who owns the system? How much federal value is reflected in the price paid by the homeowner? What happens when the house is sold? Which deadline and qualification does the provider rely on? If the salesperson cannot identify the claimant and the provision, “we still get the tax credit” is a sentence without a subject.
The Illinois Power Agency warns that homeowner-owned and third-party-owned paths have separate timing and eligibility questions after the 2025 law. Tax advice belongs with a qualified professional. Contract economics still belong in plain English before signature.
An Old Proposal Needs a Red Pencil
Take any solar proposal created before 2026 and find every place where 30 percent influences the page. It may appear in the incentive table, net cost, projected return, payback year, loan balance, monthly payment, or chart comparing solar with utility service. Removing one row while leaving the downstream calculations untouched is like erasing a river from a map while preserving the bridge.
Ask for a fresh version generated under current law. The revision date should be visible. The federal residential credit should show zero for a homeowner-owned system completed in 2026. Illinois incentives should be identified by program, utility territory, system size, ownership model, and the source date used. Financing should be shown with and without any optional principal payment.
There is a useful emotional test here too. Watch what happens when you ask for the federal credit to be removed. A careful adviser will reopen the model. A closer may change the subject to rising rates, environmental values, or a deadline unrelated to your tax return.
The green cell on that February spreadsheet took one keystroke to delete. The projected payback moved. The monthly loan path moved. The decision became less exciting and more accurate, which was the first moment the document started behaving like a financial model.
The old atlas is still on my shelf. I write “bridge closed” across the obsolete crossing so nobody in the house mistakes preservation for guidance.