Solar panels in Decatur, IL
Roofs in Decatur get about 1,497 hours of usable sunlight a year — less than 59% of the cities we've measured. Here's what that means in cost, savings and payback, using real rooftop data rather than a national average.
Check your specific roof in Decatur → City averages are a starting point; your own roof's size, pitch and shading change the answer a lot.
What a typical Decatur solar system costs
A 22-panel system (8.8 kW) is about right for an average Decatur home using 10,800 kWh a year. It would produce roughly 11,198 kWh annually and offset 100% of that usage.
| System | Size | kWh/yr | Net cost | Saves/yr | Payback |
|---|---|---|---|---|---|
| 8 panels | 3.2 kW | 4,072 | $6,384 | $664 | 9.6 yrs |
| 12 panels | 4.8 kW | 6,108 | $9,576 | $996 | 9.6 yrs |
| 16 panels | 6.4 kW | 8,144 | $12,768 | $1,327 | 9.6 yrs |
| 20 panels | 8 kW | 10,180 | $15,960 | $1,659 | 9.6 yrs |
| 26 panels | 10.4 kW | 13,233 | $20,748 | $1,860 | 11.2 yrs |
Notice that payback barely improves as systems get bigger, and eventually gets worse. That's because you can only save money on electricity you were going to buy anyway. Once a system covers your usage, extra panels mostly generate exports at a much lower rate.
Why Decatur gets 1,497 sun hours
That figure comes from Google's analysis of real rooftops across Decatur — it already accounts for shading from trees, chimneys and neighbouring buildings, which is why it's lower than the raw "hours of daylight" figures you'll see elsewhere. An unusually open, unshaded roof in Decatur reaches about 1,610 hours, roughly 8% better than typical.
The numbers behind this page
| Typical usable sunlight | 1,497 hrs/yr |
|---|---|
| Unshaded roof | 1,610 hrs/yr |
| Electricity rate (Illinois avg) | 16.3¢/kWh |
| Installed cost assumed | $2.85/W |
| Panel size assumed | 400 W |
| Federal tax credit | 30% |
| Typical household usage | 10,800 kWh/yr |
| Power used as generated | 34% |
| Paid for exported power | full retail (net metering) |
| Rooftops sampled here | 11 |
| Google imagery from | 2022 |
Nearby cities
See all of Illinois → statewide sunlight, rates, incentives and every city we've measured.
Decatur solar questions
How many solar panels do I need in Decatur?
About 22 panels for an average home. Decatur roofs get 1,497 usable sun hours a year, so each 400W panel produces roughly 509 kWh annually.
Is solar worth it in Decatur?
At 16.3¢/kWh and 1,497 sun hours, a typical system pays for itself in about 9.9 years and returns roughly $26,859 over 25 years. That is a solid return.
How much do solar panels cost in Decatur?
A 8.8 kW system costs about $25,080 before incentives and $17,556 after the 30% federal tax credit. Prices vary by installer, roof complexity and equipment.
Worth reading before you buy
Estimates only, generated 2026-08-22 from Google Solar API rooftop samples and average Illinois electricity rates. Not a quote and not financial advice. Your roof, usage, utility plan and local incentives will change these numbers — get real quotes before buying.