Do Solar Panels Increase Home Value in Illinois? What Zillow, Berkeley Lab and Fannie Mae Actually Say (2026)

Owned solar panels do increase home value, and the two best studies agree on the size of the bump: Zillow found solar homes sold for 4.1% more (about $9,274 on the median home) in its 2018–2019 sales data, and Lawrence Berkeley National Laboratory measured roughly $4 per watt, or about $15,000 for an average 3.6 kW system, across 22,822 home sales in eight states. Leased panels are a different story. Under Fannie Mae's appraisal rules, panels that are leased or under a power purchase agreement cannot be included in the appraised value at all. And in Illinois, the value an owned system adds stays off your property tax bill under 35 ILCS 200/10-10.

That's the whole answer in one paragraph. The rest of this post is the part the national articles skip: who is allowed to count the value, why the lease-versus-own question matters more than the study numbers, and what an Illinois seller has to do so the value actually shows up at closing.

Key facts: solar and home value

Updated September 30, 2026: 11.326¢ (Ameren Illinois) and 10.399¢ (ComEd) are the June 1 – September 30, 2026 rates. From October 1, 2026 through May 31, 2027, the Price to Compare is 10.441¢/kWh on the first 800 kWh and 8.262¢ above 800 for Ameren Illinois, and 10.103¢/kWh for ComEd, per the Illinois Commerce Commission's Plug In Illinois pages.

Anything below that turns those figures into a dollar amount for a specific Illinois house is my estimate. The rows above are the published numbers.

What the two studies actually measured

Zillow's number is the one everybody quotes, so it's worth knowing what it is. Zillow compared homes with and without solar that listed and sold in a single year, controlling for bedrooms, bathrooms, square footage, age and location. The solar homes sold for 4.1% more on average. Zillow's own write-up admits the premium moved a lot by market and that solar homes may also have other hard-to-measure upgrades, like heated floors, that pull the number up.

The Berkeley Lab study is older but bigger and more careful. It looked at 22,822 sales from 2002 to 2013 and found buyers "consistently willing to pay PV home premiums across various states, housing and PV markets, and home types." The premium worked out to about $4 per watt. The part I find most useful is what the premium tracked: the replacement cost of the system net of state and federal incentives, not the gross install price. A buyer, in other words, pays roughly what it would cost them to put the same system on the roof after incentives. That logic still holds in 2026, which is why I wouldn't multiply a new 8 kW system by $4 and expect $32,000. Systems cost less per watt now than they did in 2013, so the premium should be lower per watt too.

Neither study sliced out Illinois. My honest read for a $250,000 house in Belleville, Edwardsville or Springfield with an owned system is an estimated $8,000 to $12,000 of added value, closer to the Zillow percentage than the Berkeley per-watt figure. If someone quotes you a bigger number, ask which study it came from.

Who is allowed to count the value

Here's the piece that decides whether the premium is real money or a nice statistic. A home's sale price is whatever a buyer will pay, but the buyer's lender only lends against the appraised value, and for most conventional loans the appraiser follows Fannie Mae's rules. Its Selling Guide sorts solar into three buckets.

Owned outright. If the panels were paid in cash, included in the purchase price, financed and paid off, or rolled into the first mortgage, Fannie Mae's standard appraisal rules apply. The appraiser can give the system contributory value, backed by comparable sales.

Separately financed with a lien. If a solar loan uses the panels as collateral and that lien shows up in the land records, the appraiser may count the panels only if the loan documents say the panels can't be repossessed on default. If the lien doesn't appear on title, the guide tells the lender to "instruct the appraiser not to provide contributory value of the solar panels towards the appraised value because the panels are collateral for another debt." In my experience that's how most solar loans are written. The value is there for a cash buyer, but not for the appraisal.

Leased or power purchase agreement. The guide's requirement is one sentence: "The value of the solar panels cannot be included in the appraised value of the property." The lender reviews the lease, may count the payment in the buyer's debt ratio, and moves on.

One more line from the same guide matters for sellers. If the ownership status of the panels is unclear and the paperwork is missing, "no value for the panels may be attributed to the property value on the appraisal" unless the lender runs a UCC personal-property search. Translation: an owned system with no documents gets treated like a leased one. Keep your contract.

The Illinois twist: added value, not added taxes

In most states, a higher assessed value means a higher property tax bill. Illinois wrote an exception into the Property Tax Code. Section 10-10 says that when a solar energy system is installed, the owner "is entitled to claim, by filing with the chief county assessment officer, an alternate valuation of those improvements." The assessor values the home twice, once "as if equipped with a conventional heating or cooling system" and once with the solar system, and "the alternate valuation computed as the lesser of the two values" is the one that applies for as long as the system is in use.

An owned system in Illinois therefore gives you the premium at resale without the tax bill in between. You do have to claim it. I covered the PTAX-330 form and the assessor process in the property tax post, and the short version is: file it the season your system is turned on.

What a leased system does to your sale

I sell more leases than purchases, so I'm not going to pretend the appraisal rule is a footnote. If your system is leased, its value on the appraisal is zero. Full stop.

What a lease does instead is travel with the house. The buyer takes over the same per-kWh price you had, as low as $0.10 per kWh in Illinois, and compares it with what they'd otherwise pay Ameren or ComEd. Ameren's supply price alone is 11.326¢ per kWh through September 30, 2026, and ComEd's is 10.399¢, before delivery charges that add several more cents. That comparison is why I've watched buyers treat a transferred lease as a selling point rather than a liability, especially in Ameren territory where the all-in rate has climbed the way it has.

It's still a monthly-bill argument, not an equity argument. If building home equity is your goal, buy the system, file the PTAX-330, and keep the records. If a lower bill starting next month with no cash out is the goal, the lease still wins on that measure, and the state's new home-sale guide has made the transfer process more predictable than it was two years ago. I ran both paths side by side in the lease vs. buy post if you want the full math.

How to make the value show up at closing

For an owned system, the premium doesn't appear by itself. Appraisers work from comparable sales, and in a lot of Central Illinois townships there aren't three recent solar-home comps to pull. That means you and your agent have to hand the appraiser the case.

• Documents. The purchase contract, proof the loan is paid (or the payoff letter), the utility's permission-to-operate letter, and the Illinois Shines paperwork if RECs were sold. This is what Fannie Mae's guide says clears the "ownership unclear" problem.
• Production history. Twelve months from the monitoring app, plus the utility bills for the same months. A buyer who can see the bill dropped from $210 to $60 doesn't need a study.
• Ask for the energy addendum. The Appraisal Institute publishes a Residential Green and Energy Efficient Addendum that gives the appraiser a place to record system size, age, ownership and production. Ask your lender's appraiser to use it. Not every appraiser will, but the ones who do tend to be the ones who assign value.
• Check the county records. If a solar lender ever filed a UCC statement on your panels, make sure it was released when the loan was paid. An unreleased filing is the fastest way to turn an owned system into a "financed" one on the appraisal.

For a leased system, skip the value argument and prepare the transfer instead: the buyer's side of the transfer is a credit check and a signature, and the seller's side is mostly getting the leasing company started early.

The bottom line

Owned solar adds an estimated 4% or so to a home's sale price, with the Berkeley data suggesting a bit more for larger systems, and Illinois lets you keep that value off your tax bill. Leased solar adds nothing on the appraisal but transfers a lower supply price to the next owner. Which one is right depends on whether you're buying a bill reduction or a home improvement, and that's a conversation I'd rather have with your actual bill on the table than in the abstract.

Run your address through the savings calculator to see what a system would produce on your roof, or call me at (618) 217-2001 and we'll figure out which path fits. No pressure, just numbers.

Sources

• Zillow Research: Homes With Solar Panels Sell for 4.1% More (published April 16, 2019; sales March 1, 2018 – February 28, 2019)
• Lawrence Berkeley National Laboratory: Selling Into the Sun, Price Premium Analysis of a Multi-State Dataset of Solar Homes (22,822 sales, 2002–2013)
• Fannie Mae Selling Guide B2-3-04, Special Property Eligibility Considerations, "Properties with Solar Panels" (current edition, page dated October 8, 2025)
• 35 ILCS 200/10-10, Valuation of solar energy systems (Illinois Property Tax Code)
• Lake County CCAO: Solar Energy Assessment Application (PTAX-330) (county e-file page for the state form)
• Appraisal Institute: Residential Green and Energy Efficient Addendum (form PDF; solar section fields)
• Plug In Illinois: Ameren Illinois Price to Compare (11.326¢, June 1 – September 30, 2026)
• Plug In Illinois: ComEd Price to Compare (10.399¢, June 1 – September 30, 2026)