Solar panels in O'Fallon, MO
Roofs in O'Fallon get about 1,542 hours of usable sunlight a year — more than 57% 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 O'Fallon → City averages are a starting point; your own roof's size, pitch and shading change the answer a lot.
What a typical O'Fallon solar system costs
A 21-panel system (8.4 kW) is about right for an average O'Fallon home using 10,800 kWh a year. It would produce roughly 11,010 kWh annually and offset 100% of that usage.
| System | Size | kWh/yr | Net cost | Saves/yr | Payback |
|---|---|---|---|---|---|
| 8 panels | 3.2 kW | 4,194 | $6,384 | $512 | 12.5 yrs |
| 12 panels | 4.8 kW | 6,291 | $9,576 | $768 | 12.5 yrs |
| 16 panels | 6.4 kW | 8,388 | $12,768 | $1,023 | 12.5 yrs |
| 20 panels | 8 kW | 10,486 | $15,960 | $1,279 | 12.5 yrs |
| 26 panels | 10.4 kW | 13,631 | $20,748 | $1,404 | 14.8 yrs |
How we worked this out for O'Fallon
Every number on this page comes from these seven steps. Nothing is a national average — the sunlight figure is measured from O'Fallon rooftops.
| # | Step | Result |
|---|---|---|
| 1 | What one panel makes here 400W ÷ 1000 × 1,542 sun hrs × 0.85 system losses |
524 kWh/yr |
| 2 | Panels needed to cover typical usage 10,800 kWh ÷ 524 kWh per panel |
21 panels |
| 3 | System size 21 panels × 400W |
8.40 kW |
| 4 | Annual production 8.40 kW × 1,542 hrs × 0.85 |
11,010 kWh/yr |
| 5 | Installed cost 8,400 W × $2.85 per watt, then −30% federal credit |
$16,758 |
| 6 | Annual saving 3,780 kWh used as generated × 12.2¢ + 7,230 kWh exported × 12.2¢ |
$1,324/yr |
| 7 | Payback $16,758 ÷ $1,324 per year |
12.7 years |
Step 6 matters more than it looks. Only 34% of what a system this size produces in O'Fallon is used the moment it is generated; the other 7,230 kWh is exported and credited one-for-one under net metering. Because exports here are credited at or near retail, that split changes the payback very little — 12.5 years against the 12.7 we show. In places where exports pay a fraction of retail the same split moves payback by years, which is why we model it explicitly rather than assuming.
Assumptions: 400W panels, 15% system losses (inverter, wiring, heat, soiling), $2.85/W installed, 10,800 kWh typical annual household use, 12.2¢/kWh electricity. Change any of those and every figure above moves — which is exactly why a single national "solar costs X" number is misleading.
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 O'Fallon gets 1,542 sun hours
That figure comes from Google's analysis of real rooftops across O'Fallon — 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 O'Fallon reaches about 1,662 hours, roughly 8% better than typical.
The numbers behind this page
| Typical usable sunlight | 1,542 hrs/yr |
|---|---|
| Unshaded roof | 1,662 hrs/yr |
| Electricity rate (Missouri avg) | 12.2¢/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 | 10 |
| Google imagery from | 2023 |
When O'Fallon actually produces
Annual totals hide the thing that catches people out: 35% of O'Fallon's yearly sunlight arrives in May–July, and just 14% across November–January.
| Month | Sun hrs | Share of year |
|---|---|---|
| Jan | 71 | |
| Feb | 95 | |
| Mar | 125 | |
| Apr | 156 | |
| May | 178 | |
| Jun | 187 | |
| Jul | 182 | |
| Aug | 165 | |
| Sep | 136 | |
| Oct | 104 | |
| Nov | 77 | |
| Dec | 65 |
O'Fallon produces about 2.9× as much in Jun as in Dec — a normal mid-latitude swing. Expect real winter shortfall and summer surplus rather than steady year-round output.
The annual total is measured from Google's rooftop imagery. Its split across months is calculated from solar geometry at O'Fallon's latitude, not separately measured, so treat the monthly figures as the shape of a typical year rather than a forecast.
How O'Fallon compares to the other 788 cities
| Measure | O'Fallon | Rank of 788 |
|---|---|---|
| Usable sunlight | 1,542 hrs | 341st |
| Sunlight lost to shade | 7% | 199th most |
| Median roof size | 229 m² | 272nd largest |
| Electricity rate | 12.2¢ | 680th highest |
| Payback | 12.7 yrs | 618th fastest |
| Grid carbon | 892 kg/MWh | 24th dirtiest |
What actually stands out about O'Fallon:
- Plenty of roof to work with. Typical roofs here fit around 93 panels — roughly 4× what an average home needs. Roof size will not be what limits your system in O'Fallon.
- Every kWh counts more here. The grid serving O'Fallon emits 892 kg CO₂ per MWh, among the highest of the 788 cities measured — so the same panels displace more emissions than they would elsewhere.
Cities with almost the same sunlight
These are the closest matches to O'Fallon's 1,542 usable sun hours from other states and provinces. Same sunlight, different electricity prices — which is usually what decides whether solar is worth it.
| City | Sun hrs | Rate | Payback |
|---|---|---|---|
| Murfreesboro, TN | 1,541 | 12.1¢ | 12.8 yrs |
| Tyler, TX | 1,541 | 15.1¢ | 10.2 yrs |
| Kenosha, WI | 1,543 | 17.3¢ | 8.9 yrs |
| Eureka, CA | 1,540 | 31.2¢ | 10.3 yrs |
Nearby cities
See all of Missouri → statewide sunlight, rates, incentives and every city we've measured.
O'Fallon solar questions
How many solar panels do I need in O'Fallon?
About 21 panels for an average home using 10,800 kWh a year. O'Fallon roofs get 1,542 usable sun hours, so each 400W panel produces roughly 524 kWh annually. A typical O'Fallon roof fits about 93 panels, so roof space is unlikely to be your limit.
Is solar worth it in O'Fallon?
At 12.2¢/kWh and 1,542 sun hours, a typical system pays for itself in about 12.7 years and returns roughly $16,342 over a 25-year panel life. That is slower than average, so compare several quotes before committing. Exported power earns full retail credit here.
How much do solar panels cost in O'Fallon?
A 8.4 kW system costs about $23,940 before incentives and $16,758 after the 30% federal tax credit. That works out near $2.85 per watt installed. Roof pitch, shading, electrical panel upgrades and equipment choice move the price most, which is why quotes for the same house can differ by thousands.
Worth reading before you buy
Estimates only, generated 2026-08-22 from Google Solar API rooftop samples and average Missouri 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.