Solar calculator for Illinois

The average Illinois home uses 693 kWh a month and pays 15.9 cents per kWh, which puts Illinois at mid-range electricity prices, so payback depends mostly on how much sun your roof gets. Winter heating shapes the bill in Illinois, and winter is when panels make the least, so a bill that looks big in January does not map cleanly to a bigger array. A south-facing fixed array there makes about 1,308 kWh per installed kW a year, and the worst winter month still gets 2.17 peak sun hours a day. Drop in your own bill below and the numbers on this page are replaced by yours.

A worked example for Illinois

Take the average home: 693 kWh a month, which is 8,316 kWh a year, at 15.9 cents per kWh (EIA, 2024 residential averages, as of 2026-11). Sized to cover all of that use, the tool returns 6.4 kWdc and 16 panels, needing about 336 square feet of roof. The installed estimate is $15,831 (national median, EnergySage H2 2025), yearly savings are about $1,322, and simple payback is 12.0 years, with no incentive applied.

Sun and yield in Illinois

We use 1,308 kWh per installed kW per year for Illinois, from NREL PVWatts v8 for the state's largest city at a 20 degree south-facing tilt (via TheGreenWatt, as of 2026-11). The darkest month averages 2.17 peak sun hours a day, which matters if you plan to go off-grid or size a battery. A different roof angle or heavy shade changes this, so treat it as a starting point.

Incentives

The 30% federal tax credit ended for homeowner purchases after December 31, 2025, so none is applied here. See the tax credit guide. Look up Illinois and your own utility for net metering terms and any local programs before relying on a payback number.

Planning estimate. Permits, interconnection approval and a licensed electrician are required for grid-tied systems.

Questions