The drawings, and who has to produce them
Peoria requires a Residential Solar Voltaic Building Permit application supported by construction drawings that include structural information and a site plan scaled by an engineer or an architect. That is a higher bar than a form and a product brochure, and it puts a licensed professional in the process before installation begins.
The reason to know this early is that it changes who you should be talking to. A company that installs in Peoria regularly will have a working relationship with an engineer or architect and will treat the requirement as routine. One that does not may discover it after taking a deposit, which is where timelines slip. Ask directly how they produce the structural information and the scaled site plan, and whether that cost is inside the quoted price or added later.
On fees, the Fire Solar Voltaic Permit Fee is $100, and building permit fees are otherwise based on total construction cost. So permit cost here scales with project cost rather than being a flat charge, which is worth knowing when you compare a modest array against a larger one.
Ameren Illinois and supply-only crediting
As of 2025, new residential and small commercial net metering customers in Ameren Illinois territory moved from full retail rate net metering to supply-only net metering. An exported kilowatt-hour is credited against the electricity supply portion of your bill rather than at the full retail rate you pay to buy power back.
Your bill divides into supply, the electricity itself, and delivery, the network that brings it. Self-consumed generation avoids both because you never purchase that kilowatt-hour. Exported generation earns credit against the supply half only. The practical consequence is that the value of a system depends on when you use power as much as on how much the array makes.
Two responses follow, and both are cheap. Size the system against twelve months of your own bills rather than against roof area, because capacity beyond your consumption earns the narrower credit. And shift what you can into daylight hours, since running the laundry, the dishwasher or an EV charger while the array is producing converts an export credit into an avoided retail purchase.
What a Peoria roof produces
The planning figure is roughly 1,297 kWh a year for every kW installed, derived from satellite irradiance data with a standard performance ratio applied rather than measured from local systems. Treat it as the screening number and let the site survey produce the figure that belongs in a contract.
Orientation, pitch, shade and usable area do the rest. South-facing planes generate across the whole day while east and west faces load one end of it. Pitch affects both output and how fast snow clears. Usable area is what is left once vents, stacks, chimneys and setbacks are removed, and it is reliably smaller than the roof appears from the street.
Because the permit package already requires structural information, this is a good city in which to ask for the roof's condition and structure to be assessed properly as part of the design rather than assumed. If the roof covering is near the end of its life, ask what removing and reinstalling the array would cost when the roof is replaced, and whether doing the roof first is the cheaper sequence.
Who controls the roof in Peoria
Single-detached houses are 63.1 percent of the 54,010 housing units here, so most residents own the roof and the decision.
The multifamily share is concentrated in mid-sized and larger buildings: 7.6 percent of units sit in buildings of 5 to 9 units, 6.9 percent in buildings of 10 to 19, and 11.1 percent in buildings of 20 or more. In all of those the roof belongs to the building owner or the association, a resident cannot commission an installation alone, and an array on the building normally offsets a building account rather than an individual apartment.
If you rent or own in one of those buildings, the productive move is to ask the owner or the board whether they have looked at it, and to point them at the same questions: what the roof can carry, what the supply-only credit is worth against the building's own consumption, and what Illinois Shines would pass through on a project that size.
Incentives worth chasing, and one that is gone
Illinois Shines, the Adjustable Block Program administered by the Illinois Power Agency, pays Renewable Energy Credit money to Approved Vendors, who may pass the value on as reduced equipment or installation cost. Using an Approved Vendor is a condition of participating, and how much is passed through varies between vendors, so ask each for the Disclosure Form that states it. Two quotes cannot be compared properly without those forms.
Illinois Solar for All is the income-based program and works differently, serving homeowners, renters through community solar and multifamily building owners on terms structured so participants pay less for electricity than they would have without solar.
The 30 percent federal residential tax credit under Section 25D is not available on a 2026 purchase. It applied through December 31, 2025 and does not cover a purchased home system placed in service after that date. Some sources you may be pointed at have not been updated and still describe it as current, so rebuild any payback figure that includes it. Where a homeowner takes a lease or a power purchase agreement instead, the provider may claim the business credit under Section 48E and reflect part of the value in the rate, which is a question for the provider and a tax advisor.