Adding solar to a new build or remodel in Illinois

The roof, walls and electrical service are already open, so the parts that make a later install expensive, such as running conduit, upgrading the panel or reinforcing the roof, cost far less. Installing over a brand-new roof also means you won't pay to remove and reinstall the panels when the roof wears out, which Fixr puts at about $3,800 on average for a typical array. See should I replace my roof before solar?

The model building codes' solar-ready provisions, which towns can adopt, give a good checklist. They apply to homes with at least 600 square feet of roof facing between east and west through south, and ask for:

• A solar-ready zone of at least 300 square feet, kept clear of vents, skylights and other obstructions.
• A documented pathway for conduit from the roof to the main electrical panel.
• Roof structure designed for the added weight, with the design loads shown on the plans.
• Space in the electrical panel reserved for the solar breaker.

Going further than the code is cheap now: run the conduit instead of just showing the route, leave wall space near the panel for an inverter and a battery, and keep large trees off the south side. A garage wall is a common battery spot; see whole-home battery backup.

Not statewide. Illinois bases its energy code on the International Energy Conservation Code: the 2021 edition took effect January 1, 2024, and the state has since adopted the 2024 edition. The base code doesn't make new homes install or prepare for solar.

The Illinois Stretch Energy Code, available since January 1, 2025, adds solar-ready, EV-ready and electric-ready requirements, but only in towns that choose to adopt it. Evanston was the first, starting October 1, 2025. Ask your builder or village which code applies to your permit.

In Chicago, the 2022 Energy Transformation Code requires new homes with gas appliances to have the electrical capacity and wiring to switch to electric appliances later, which also helps with solar and EV charging.

Most new homes get 200-amp service, which is enough for solar on most homes. The catch is the panel. The electrical code's "120% rule" limits how much solar can feed back into a panel to 120% of the panel's busbar rating minus its main breaker.

For context, a system sized for a $250 monthly ComEd bill is about 14 kW in our estimates. If yours will be big, or you plan EV chargers, a heat pump or a battery, ask your electrician about a 225-amp busbar, a supply-side connection or a larger service. Those choices cost little at rough-in and much more after the walls are closed.

Solar connects to the grid through ComEd or Ameren's interconnection process, which follows the home's permanent electric service and the town's electrical inspection. Small systems use the simplest Level 1 review, and Ameren must schedule any witness test within 10 business days of commissioning or it's waived. Budget a few weeks to a couple of months after move-in; see how long solar installation takes.

Apply for the $300/kW utility rebate and Illinois Shines through your installer as usual. Illinois Shines treats a new home like any other, but net metering now credits exported power at the supply rate, so size the system to your expected daytime use. See Illinois net metering.

• Fannie Mae HomeStyle Energy lets you finance energy upgrades, including solar, when you buy or refinance, up to 15% of the home's as-completed appraised value.
• FHA loans have a solar and wind option for systems costing up to 20% of the property's value.
• Construction loans can often include solar as a line item, if the lender and appraiser account for it. Ask before the budget is final.

A mortgage rate is usually lower than a solar loan's, with no dealer fee, though you'll pay it over a longer term. See solar loans and dealer fees.

No, for homes you move into after 2025. The homeowner's 30% credit ended for expenditures after December 31, 2025, and for new construction the IRS treats the expense as made when you start living in the home. Leased systems and power purchase agreements can still carry a business credit for the installer. See the federal solar tax credit in 2026.