Solar panels in St. Louis, MO: payback and output
A kW of south-facing panels in St. Louis produces about 1,371 kWh a year, 4% less than Kansas City, the Missouri reference city. Summer months produce 1.8× what winter does. To cover a typical 10,500 kWh/yr home on paper you'd need roughly 7.7 kW.
Output by month in St. Louis (kWh per kW)
Best: Jun · weakest: Dec.
Example 7 kW system in St. Louis
- Installed cost (example)
- $21,000
- Production, year 1
- 9,594 kWh
- Savings, year 1
- $1,544
- Payback
- 12.8 years
- 25-year net gain
- $25,863
Uses the Missouri average price (16.09¢/kWh, EIA July 2026), full net metering and no incentives. Your utility's rate and export credit may differ — change them below.
Roof direction in St. Louis
Yearly output per kW of panels at a 20° pitch, and how it compares with a south-facing roof.
| Roof faces | kWh per kW/yr | vs. south |
|---|---|---|
| South | 1,371 | — |
| Southeast | 1,308 | −5% |
| Southwest | 1,315 | −4% |
| East | 1,162 | −15% |
| West | 1,169 | −15% |
| East-west (split) | 1,166 | −15% |
Calculate your home in St. Louis
Estimated payback
12.8 years
A solid case if you plan to stay in the home.
≈ $129/month off your bill in year 1
- Year-1 savings
- $1,544
- 25-yr net gain
- $25,863
- Return (IRR)
- 6.7%
- Net cost
- $21,000
Cumulative savings minus cost
Production vs. use by month
9,594 kWh/yr
Covers 40% of your use directly; 44% of the output is used on the spot.
Which size pays off best?
Same usage and prices, only size changes. Best 25-year gain: 8 kW.
| Size | Cost | Year-1 savings | Payback | 25-yr gain |
|---|---|---|---|---|
| 3 kW | $9,000 | $662 | 13.8 years | $9,656 |
| 4 kW | $12,000 | $882 | 13.3 years | $13,707 |
| 5 kW | $15,000 | $1,103 | 13.1 years | $17,759 |
| 6 kW | $18,000 | $1,323 | 12.9 years | $21,811 |
| 7 kW | $21,000 | $1,544 | 12.8 years | $25,863 |
| 8 kW | $24,000 | $1,689 | 12.9 years | $29,533 |
| 10 kW | $30,000 | $1,689 | 15.5 years | $25,208 |
| 12 kW | $36,000 | $1,689 | 18.0 years | $19,208 |
Read the full Missouri solar guide for net metering, orientation and price trends.
Other cities in Missouri
Cities with similar sunshine
Solar in St. Louis: common questions
Are solar panels worth it in St. Louis, MO?
For an example 7 kW system costing $21,000 on a home using 10,500 kWh a year, payback in St. Louis is 12.8 years with full net metering and 17.1 years if exports earn half the retail rate, at the Missouri average price of 16.09¢/kWh (EIA, July 2026).
How much electricity do solar panels produce in St. Louis?
About 1,371 kWh per year for each kW of south-facing panels at a 20° pitch (NLR PVWatts, typical-year weather), from 73 kWh in Dec to 146 kWh in Jun.
What size solar system does a home in St. Louis need?
About 7.7 kW to cover 10,500 kWh a year. Divide your own annual use by 1,371 kWh per kW for a first estimate; if exports earn less than retail, a smaller system often pays back faster.
Does roof direction matter in St. Louis?
Yes. Per kW at a 20° pitch: south 1,371 kWh, southeast 1,308 kWh, southwest 1,315 kWh, east 1,162 kWh, west 1,169 kWh, east-west (split) 1,166 kWh a year. South-facing roofs produce the most; east or west roofs still work, with less output.
Guides for going solar in St. Louis
- Payback · 4 minIs solar still worth it without the 30% federal tax credit?The 30% federal solar credit is gone for new systems. We ran payback for every state without it, and compared it with what the credit used to do.
- Planning · 3 minHow many solar panels do I need? Sizing from your electric billA step-by-step way to size a home solar system from your annual kWh, daytime use and local sunshine, with real size-vs-payback tables for four states.
- Payback · 4 minNet metering vs. net billing: how export credits change paybackHow much your utility pays for exported solar power can add years to payback. We compare full, half and quarter-retail credits in every state.
- Planning · 6 minEast- or West-Facing Roof: Is Solar Still Worth It?East- or west-facing solar panels made about 14.5% to 14.8% less power than south-facing ones across U.S. states. See where the loss is biggest and smallest.
- Planning · 6 minSolar Panels in Winter: Output by State vs. SummerHow much do solar panels make in winter? Winter vs. summer output per kW for U.S. states, why the gap grows up north, and what it means for net metering.
- Payback · 5 minRising electricity prices: where solar pays back fastestCompare electricity prices and solar payback by state: see where a rooftop system pays back fastest, where it is slowest, and why credit rules matter.
Data: NLR PVWatts v8 (U.S. DOE National Laboratory of the Rockies, formerly NREL), TMY weather near St. Louis (38.63, -90.2), 14% losses, retrieved 2026-10-11. Published 2026-10-15.