Solar in Illinois: payback, sun by city and utility-scale capacity
Across 5 Illinois cities, yearly output runs from 1,333 kWh per kW in Chicago to 1,378 in Springfield. Jul is the best month at 155 kWh per kW and Dec the worst at 67. Illinois pays back in 13.0 years at $3.00 a watt (rank 24 of 51), 0.5 years shorter than the middle state. 1,308 kWh per kW (rank 37) at 17.69 ¢ (rank 17 from the top): price of power drives it. Utility-scale solar in Illinois: 4,389 MW in 410 plants, 3.5% of 2025 generation; 4,836 MW more under construction or planned.
Sun inside Illinois: 5 cities, 3% apart
| Illinois city | kWh per kW a year | Against state point | Sun, kWh/m2 a day | Payback at $3.00 | Residents |
|---|---|---|---|---|---|
| Chicago | 1,333 | +1.9% | 4.61 | 12.7 | 2,707,648 |
| Aurora | 1,336 | +2.2% | 4.65 | 12.7 | 179,867 |
| Rockford | 1,348 | +3.1% | 4.67 | 12.6 | 147,649 |
| Springfield | 1,378 | +5.4% | 4.81 | 12.3 | 113,714 |
| Peoria | 1,368 | +4.6% | 4.77 | 12.4 | 112,126 |
Illinois state point 41.41, -88.30; city points Chicago 41.84, -87.69; Aurora 41.76, -88.29; Rockford 42.26, -89.06; Springfield 39.79, -89.64; Peoria 40.75, -89.62. Panel and method: solar method.
Output by month in Illinois cities: 12 rows
| Illinois month | Chicago | Aurora | Rockford | Springfield | Peoria |
|---|---|---|---|---|---|
| Jan | 63.4 | 74.5 | 74.9 | 74.8 | 74.5 |
| Feb | 85.4 | 86.1 | 87.8 | 91.2 | 85.1 |
| Mar | 113.9 | 113.1 | 115.4 | 119.2 | 116.8 |
| Apr | 133.4 | 124.6 | 125.8 | 131.9 | 127.2 |
| May | 140.8 | 132.8 | 142.9 | 134.1 | 140.2 |
| Jun | 148.0 | 142.8 | 146.1 | 148.6 | 149.8 |
| Jul | 156.3 | 151.4 | 149.8 | 150.5 | 156.4 |
| Aug | 141.5 | 150.9 | 145.9 | 138.3 | 145.0 |
| Sep | 122.2 | 122.4 | 122.9 | 129.2 | 133.1 |
| Oct | 95.9 | 99.7 | 97.8 | 109.6 | 102.0 |
| Nov | 72.4 | 74.1 | 78.2 | 83.6 | 75.1 |
| Dec | 59.9 | 63.8 | 60.2 | 66.5 | 63.2 |
Illinois: 5 cities, best month 156 and worst 60 kWh per kW across them.
CSVBest and worst month in Illinois: Jul 155, Dec 67 kWh per kW
| Illinois month | kWh per kW | Price ¢ | Value per kW | kWh per kW per sun unit |
|---|---|---|---|---|
| Jan | 71.1 | 15.78 | $11.22 | 0.87 |
| Feb | 82.3 | 16.47 | $13.55 | 0.84 |
| Mar | 110.3 | 17.55 | $19.36 | 0.82 |
| Apr | 125.6 | 18.28 | $22.96 | 0.80 |
| May | 129.1 | 18.58 | $23.99 | 0.77 |
| Jun | 141.8 | 18.29 | $25.94 | 0.75 |
| Jul | 155.4 | 17.22 | $26.76 | 0.74 |
| Aug | 137.2 | 18.06 | $24.78 | 0.75 |
| Sep | 117.7 | 19.05 | $22.42 | 0.77 |
| Oct | 99.2 | 18.74 | $18.59 | 0.80 |
| Nov | 71.2 | 18.31 | $13.04 | 0.84 |
| Dec | 66.7 | 17.07 | $11.39 | 0.86 |
Illinois: December to February give 17% of a year (rank 17 of 51, 1 = most winter); the best month is 2.3 times the worst. Output per unit of sun is highest in Jan (0.87) and lowest in Jul (0.74); PVWatts lowers cell output when the panel is hot, and the sun angle changes with the season. Our runs use one fixed 14% loss figure for every place, so snow or soiling in Illinois is not modelled separately.
Illinois: payback 13.0 years, rank 24 of 51
| Measure | Value | Rank of 51 | Median state |
|---|---|---|---|
| Output of 1 kW a year, kWh | 1,308 | 37 | 1,372 |
| Home price, ¢ per kWh | 17.69 | 17 | 15.37 |
| Value of 1 kW a year | $231 | 24 | $222 |
| Payback at $3.00 a watt | 13.0 years | 24 | 13.5 years |
EIA-861 (2024): 136,013 home net-metered systems in Illinois, 25.2 per 1,000 accounts (rank 18), average 7.4 kW.
Utility-scale solar in Illinois: 4,389 MW
Illinois: 4,389 MW of operable utility-scale solar in 410 plants across 75 counties (EIA-860, 2025), rank 11 of 51; 346 W per resident, rank 23. Solar made 3.5% of Illinois's net generation in 2025 (EIA-923), rank 26, -3.3 points against the national share. Biggest plants: Double Back Diamond in Sangamon County, 593 MW (2024); Emily Solar, LLC in Cumberland County, 274 MW (2025); Maple Flats in Clay County, 250 MW (2024). By county: Sangamon 593 MW, White 299 MW, Cumberland 274 MW, Saline 270 MW. Proposed: 2,079 MW under construction (140 plants) and 2,757 MW planned (42 plants); batteries 100 MW running and 202 MW proposed.
| Illinois year | MW added | Cumulative share of today's MW |
|---|---|---|
| 2019 | 4 | 0% |
| 2020 | 83 | 2% |
| 2021 | 539 | 14% |
| 2022 | 240 | 20% |
| 2023 | 370 | 28% |
| 2024 | 1791 | 69% |
| 2025 | 1320 | 99% |
Sizes and prices per watt in Illinois
| Illinois kW | kWh a year | Value a year | Cost at $2.50 | At $3.00 | At $3.50 | t CO2 |
|---|---|---|---|---|---|---|
| 4 | 5,231 | $925 | $10,000 | $12,000 | $14,000 | 1.1 |
| 6 | 7,846 | $1,388 | $15,000 | $18,000 | $21,000 | 1.7 |
| 8 | 10,462 | $1,851 | $20,000 | $24,000 | $28,000 | 2.2 |
| 10 | 13,077 | $2,313 | $25,000 | $30,000 | $35,000 | 2.8 |
| 12 | 15,692 | $2,776 | $30,000 | $36,000 | $42,000 | 3.4 |
| Illinois $ per watt | 100% retail | 75% | 50% | 25% |
|---|---|---|---|---|
| $2.00 | 8.6 | 11.5 | 17.3 | 34.6 |
| $2.50 | 10.8 | 14.4 | 21.6 | 43.2 |
| $3.00 | 13.0 | 17.3 | 25.9 | 51.9 |
| $3.50 | 15.1 | 20.2 | 30.3 | 60.5 |
| $4.00 | 17.3 | 23.1 | 34.6 | 69.2 |
Illinois: 1,308 kWh/kW × 17.69 ¢ = 231 a year per kW; the 30% column (9.1 years at $3.00) is arithmetic only.
CSVNet metering and CO2 in Illinois
EIA-861 (2024): 136,013 home net-metered systems in Illinois, 25.2 per 1,000 accounts (rank 18), average 7.4 kW.
6 kW in Illinois: 7,846 kWh a year displaces 1.7 t CO2 at 0.214 kg per kWh, -1.3 t against the average state.
Illinois among its neighbours
| Closest to Illinois | Payback, years | kWh per kW | Price, ¢ | Utility-scale solar, points of generation | Miles away |
|---|---|---|---|---|---|
| Illinois (this page) | 13.0 | 1,308 | 17.69 | 3.5 | - |
| Indiana | +0.5 | +62 | -1.46 | +2.7 | 135 |
| Wisconsin | -0.5 | +17 | +0.47 | +2.5 | 151 |
| Michigan | -1.3 | -28 | +2.32 | -1.3 | 235 |
| Iowa | +3.0 | +65 | -3.97 | -1.8 | 247 |
Illinois against its neighbours in the payback ranking
Illinois utilities and solar payback
| Illinois utility | Homes | Price ¢ | Value of 1 kW | Payback at $3.00 |
|---|---|---|---|---|
| Commonwealth Edison Co | 3,727,675 | 13.39 | $175 | 17.1 yr |
| Ameren Illinois Company | 1,060,894 | 11.76 | $154 | 19.5 yr |
| City of Springfield | 59,621 | 11.95 | $156 | 19.2 yr |
| City of Naperville | 56,117 | 12.98 | $170 | 17.7 yr |
| Corn Belt Energy Corporation | 34,710 | 15.76 | $206 | 14.6 yr |
| Southwestern Electric Coop Inc | 24,822 | 13.68 | $179 | 16.8 yr |
| Southeastern IL Elec Coop, Inc | 22,731 | 14.47 | $189 | 15.9 yr |
| Norris Electric Coop | 18,074 | 15.08 | $197 | 15.2 yr |
| Jo-Carroll Energy, Inc | 17,227 | 19.79 | $259 | 11.6 yr |
| Tri-County Electric Coop, Inc (IL) | 16,197 | 16.04 | $210 | 14.3 yr |
| City of St Charles | 14,181 | 15.37 | $201 | 14.9 yr |
| Egyptian Electric Coop Assn | 13,707 | 15.53 | $203 | 14.8 yr |
Your numbers for Illinois
Limits in Illinois
Illinois: with the old 30% credit (IRS, ended 2025) payback would be 9.1 years instead of 13.0, so the calculator starts at 0%. No Illinois export rates in our data: output counts at 17.69 ¢. All limits.
Sources for Illinois
- PVWatts v8 (NLR), 5 Illinois cities and one state point: 1,308 kWh per kW
- EIA-860 2025 and EIA-923 2025: 4,389 MW of solar in Illinois
- EIA-861 2024: 136,013 net-metered systems in Illinois
- EIA retail sales 2025: 17.69 ¢ per kWh in Illinois
- IRS 25D (ended 2025): 9.1 years in Illinois with it; licences and periods for Illinois
More about Illinois
Illinois electricity hub, Illinois EV charging: 1,871 stations, where Illinois ranks for rooftop solar, 13.0 years against 51 states, Illinois calculators.
Questions
Where in Illinois is solar best?
Yes: 3% between Chicago and Springfield in yearly output.
Illinois sunshine for solar panels?
1,308 kWh per kW a year at the state point, rank 37 of 51; from 1,333 in Chicago to 1,378 in Springfield.
Winter cut in Illinois solar output?
December to February give 17% of the year; Jul makes 155 kWh per kW and Dec 67.
Net metering in Illinois?
136,013 systems, 25.2 per 1,000 accounts, rank 18.
Illinois utility-scale solar capacity?
4,389 MW in 410 plants (EIA-860), 346 W per resident, rank 23; 4,836 MW proposed.
Solar payback in Illinois?
13.0 years at $3.00 a watt; 10.8 at $2.50; 15.1 at $3.50; 1,308 kWh per kW at 17.69 ¢.
Illinois electricity from solar, what share?
3.5% of 2025 net generation, rank 26 of 51, -3.3 points against the nation.
Illinois pays half price for exports?
Payback 25.9 years at a 50% retail share.
CO2 displaced in Illinois?
1.7 t a year on 6 kW at 0.214 kg per kWh.
Federal solar credit in Illinois: still available?
Ended 2025 (IRS 25D); with it Illinois payback would be 9.1 years, not 13.0.