Solar Panel Calculator for Saint Louis, MO
Estimate the cost, savings and payback of solar panels in Saint Louis, MO, using local NREL sunshine data, Missouri prices and electricity rates.
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Saint Louis gets about 4.92 peak sun hours a day on a south-facing roof, so each kW of panels makes about 1,395 kWh a year. That ranks #64 of the 111 cities on this site. Output peaks in Jul and is lowest in Dec.
Sunshine in Saint Louis by month
What an 8 kW system makes in Saint Louis
| Month | Sun hours a day | Output | Bill savings |
|---|---|---|---|
| Jan | 3.07 | 648 kWh | $93 |
| Feb | 4.07 | 768 kWh | $110 |
| Mar | 4.54 | 912 kWh | $130 |
| Apr | 5.97 | 1,120 kWh | $160 |
| May | 5.58 | 1,056 kWh | $151 |
| Jun | 6.30 | 1,120 kWh | $160 |
| Jul | 6.53 | 1,192 kWh | $170 |
| Aug | 6.13 | 1,112 kWh | $159 |
| Sep | 5.97 | 1,064 kWh | $152 |
| Oct | 4.47 | 872 kWh | $125 |
| Nov | 3.72 | 728 kWh | $104 |
| Dec | 2.75 | 576 kWh | $82 |
| Year | 4.92 | 11,160 kWh | $1,594 |
Savings at 14.28¢ per kWh (Missouri average), with every kWh credited at that price.
Cost and payback by system size
At $2.49 per watt, the Missouri average, before incentives.
| System | Cost | Year 1 savings | Payback | 25-yr gain |
|---|---|---|---|---|
| 4 kW | $9,960 | $797 | 12.9 yrs | $8,810 |
| 6 kW | $14,940 | $1,195 | 12.9 yrs | $13,215 |
| 8 kW | $19,920 | $1,594 | 12.9 yrs | $17,620 |
| 10 kW | $24,900 | $1,992 | 12.9 yrs | $22,025 |
| 12 kW | $29,880 | $2,390 | 12.9 yrs | $26,430 |
How many panels you need in Saint Louis
| Monthly use | System | 400 W panels |
|---|---|---|
| 500 kWh | 4.30 kW | 11 |
| 750 kWh | 6.45 kW | 17 |
| 1,000 kWh | 8.60 kW | 22 |
| 1,500 kWh | 12.90 kW | 33 |
| 2,000 kWh | 17.20 kW | 44 |
Covering 100% of a year's use at 1,395 kWh per kW.
Common questions
Is solar worth it in Saint Louis?
At local averages an 8 kW system costs about $19,920 before incentives, saves about $1,594 in its first year and pays back in about 12.9 years.
How many peak sun hours does Saint Louis get?
About 4.92 a day over the year on a south-facing roof at 20°, from 2.8 in Dec to 6.5 in Jul, according to NREL's PVWatts model.
How much does a 1 kW solar system produce in Saint Louis?
About 1,395 kWh a year, or 116 kWh a month on average.
Is there a federal solar tax credit?
Not for homeowners who buy their system. The 30% Residential Clean Energy Credit ended for systems installed after December 31, 2025.
Sources
- NREL PVWatts V8 API (south-facing, 20° tilt, 14% losses, typical-year weather): https://developer.nlr.gov/docs/solar/pvwatts/v8/
- EnergySage, Solar panel cost by state (updated November 6, 2026): https://www.energysage.com/local-data/solar-panel-cost/
- U.S. EIA, Electric Power Monthly, Table 5.6.B (residential price, Jan–Aug 2026): https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_b