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How many solar panels to charge an EV in St. Louis, MO
Short answer: About 5 solar panels of 400 W (2.0 kW) would produce the 2,363 kWh a typical U.S. EV-owning household uses for charging in a year, because NREL's PVWatts estimates 1,388 kWh per year from each kW of panels in St. Louis.
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How is the number of panels calculated?
| EV charging energy per year | 2,363 kWh per year: average annual household electricity use for EV charging in U.S. homes with EVs (2020). U.S. DOE Vehicle Technologies Office, Fact of the Week #1307 (Sept 11, 2023), citing EIA 2020 RECS (accessed 2026-10-25) |
|---|---|
| Solar output in St. Louis | 1,388 kWh AC per kW per year (1387.9 exact). PVWatts V8 API call; NREL/NLR PVWatts V8 API (NSRDB PSM V3 TMY weather; 1 kW DC, standard module, fixed open rack, 20° tilt, 180° azimuth, 14% losses). Location: St. Louis city interior point 38.635699, -90.244582 (U.S. Census Bureau 2024 Gazetteer Files – Places (interior point lat/lon)); weather cell 38.65, -90.26, 2.1 km away (NSRDB PSM V3 GOES tmy-2020 3.2.0). Accessed 2026-10-25. |
| Panel size used | 400 W. “Almost every solar panel used today is rated at 400 watts (W) or higher”; the most common size quoted on EnergySage in H1 2026 was 430–440 W. EnergySage – How many solar panels do I need? (2026 guide) (accessed 2026-10-25) |
| Math | 2,363 kWh ÷ 1,387.9 kWh per kW = 1.70 kW; 1.70 kW × 1,000 ÷ 400 W = 4.26 → 5 panels (rounded up) |
| Result | 5 panels (2.0 kW) |
Run with the public DEMO_KEY on 2026-10-25 (the API now lives at developer.nlr.gov; NREL was renamed the National Laboratory of the Rockies). PVWatts no longer accepts street addresses, so we used the city's Census interior point. Real output depends on your roof direction, tilt, shading and panel model; 430–440 W panels would cut the count. The 2,363 kWh is a 2020 national household average, not your car or mileage. Solar produces in daytime, so charging at night relies on net metering or a battery; this is an energy-equivalent count, not a guarantee of savings.
What would that solar system cost?
| Basis | Price per watt | Cost before incentives (math) |
|---|---|---|
| EnergySage national average | $2.60/W | 5 × 400 W = 2,000 W × $2.60/W = $5,200 |
| EnergySage 4 kW system average (small systems) | $2.89/W | 2,000 W × $2.89/W = $5,780 |
| EnergySage MO state average | $2.49/W | 2,000 W × $2.49/W = $4,980 |
Source: Systems average about $2.60 per watt before incentives (EnergySage Marketplace; page updated Jun 30, 2026, data auto-updated Oct 16, 2026). Smaller systems cost more per watt: 4 kW averages $2.89/W. EnergySage – Solar panel cost in 2026 (accessed 2026-10-25). Quoted marketplace prices, not installed-price statistics; your quote will differ.
Is there a federal tax credit for home solar?
No, not for new installs. The federal Residential Clean Energy Credit (section 25D, 30% for solar) is not allowed for any expenditures made after December 31, 2025; an expenditure counts as made when installation is completed. Source: IRS – FAQs for modification of sections 25C, 25D, 25E, 30C, 30D… under Public Law 119-21 (OBBB), FS-2025-05 (accessed 2026-10-25).
How many solar panels does it take to charge an EV in St. Louis?
About 5 × 400 W panels. Math: 2,363 kWh ÷ 1,387.9 kWh per kW = 1.70 kW; 1.70 kW × 1,000 ÷ 400 W = 4.26 → 5 panels (rounded up). Inputs: DOE's 2,363 kWh/year household EV charging average and NREL PVWatts V8 output for St. Louis.
How much solar does 1 kW produce in St. Louis?
PVWatts V8 estimates 1,388 kWh AC per year for a 1 kW fixed system at 20° tilt facing south with 14% losses, using NSRDB typical-year weather near St. Louis.
What would 5 panels cost?
About $5,200 at EnergySage's national average of $2.60/W before incentives (5 × 400 W = 2,000 W × $2.60/W = $5,200). Small systems cost more per watt; at EnergySage's 4 kW average of $2.89/W it is $5,780.
Is there still a federal solar tax credit?
The federal Residential Clean Energy Credit (section 25D, 30% for solar) is not allowed for any expenditures made after December 31, 2025; an expenditure counts as made when installation is completed.
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