Solar · Cooling & fans
How many solar panels to run a box fan?
A typical box fan uses about 0.80 kWh a day in the months you use it (about 120 days a year), based on 100 W for 8 hours a day, 120 days a year (96 kWh/yr). Off-grid with a battery, that takes about 390 W of solar panels (2 × 200 W) to keep up in December, the worst month in Tennessee (the middle state for sunshine), or 280 W in an average month, plus a battery of about 950 Wh. On a grid-tied home system it adds about 96 kWh a year: 0.07 kW, or 1 × 400 W panel.
Can a panel and battery keep it running where you are?
Your situation: keeping a box fan running on solar. Different situation?
Your battery and panel
Where and how
Watts and hours for a different model or use: change them on the off-grid sizer, which adds up several appliances.
By state
Off-grid columns size the panels for the month named (with 85% charging and 85% inverter losses). The grid-tied column covers its yearly use on a home system.
Panels to run a box fan in every state
| State | Off-grid, worst month | Off-grid, average month | Grid-tied, 400 W panels |
|---|---|---|---|
| Alabama | 360 W | 270 W | 1 |
| Alaska | 1,700 W | 380 W | 1 |
| Arizona | 260 W | 220 W | 1 |
| Arkansas | 350 W | 270 W | 1 |
| California | 300 W | 230 W | 1 |
| Colorado | 280 W | 240 W | 1 |
| Connecticut | 400 W | 280 W | 1 |
| Delaware | 380 W | 280 W | 1 |
| District of Columbia | 370 W | 280 W | 1 |
| Florida | 300 W | 260 W | 1 |
| Georgia | 340 W | 270 W | 1 |
| Hawaii | 300 W | 250 W | 1 |
| Idaho | 510 W | 260 W | 1 |
| Illinois | 470 W | 290 W | 1 |
| Indiana | 490 W | 290 W | 1 |
| Iowa | 450 W | 280 W | 1 |
| Kansas | 340 W | 260 W | 1 |
| Kentucky | 450 W | 290 W | 1 |
| Louisiana | 340 W | 270 W | 1 |
| Maine | 440 W | 290 W | 1 |
| Maryland | 380 W | 280 W | 1 |
| Massachusetts | 410 W | 290 W | 1 |
| Michigan | 620 W | 310 W | 1 |
| Minnesota | 490 W | 290 W | 1 |
| Mississippi | 350 W | 270 W | 1 |
| Missouri | 380 W | 270 W | 1 |
| Montana | 500 W | 280 W | 1 |
| Nebraska | 380 W | 270 W | 1 |
| Nevada | 270 W | 220 W | 1 |
| New Hampshire | 420 W | 290 W | 1 |
| New Jersey | 400 W | 290 W | 1 |
| New Mexico | 250 W | 210 W | 1 |
| New York | 390 W | 280 W | 1 |
| North Carolina | 330 W | 270 W | 1 |
| North Dakota | 510 W | 280 W | 1 |
| Ohio | 550 W | 300 W | 1 |
| Oklahoma | 320 W | 260 W | 1 |
| Oregon | 680 W | 310 W | 1 |
| Pennsylvania | 410 W | 290 W | 1 |
| Rhode Island | 390 W | 280 W | 1 |
| South Carolina | 320 W | 260 W | 1 |
| South Dakota | 410 W | 270 W | 1 |
| Tennessee | 390 W | 280 W | 1 |
| Texas | 340 W | 270 W | 1 |
| Utah | 420 W | 250 W | 1 |
| Vermont | 630 W | 310 W | 1 |
| Virginia | 340 W | 270 W | 1 |
| Washington | 780 W | 320 W | 1 |
| West Virginia | 500 W | 300 W | 1 |
| Wisconsin | 500 W | 290 W | 1 |
| Wyoming | 340 W | 250 W | 1 |
FAQ
How many solar panels to run a box fan?
A typical box fan uses about 0.80 kWh a day in the months you use it (about 120 days a year), based on 100 W for 8 hours a day, 120 days a year (96 kWh/yr). Off-grid with a battery, that takes about 390 W of solar panels (2 × 200 W) to keep up in December, the worst month in Tennessee (the middle state for sunshine), or 280 W in an average month, plus a battery of about 950 Wh. On a grid-tied home system it adds about 96 kWh a year: 0.07 kW, or 1 × 400 W panel.
Can a 200 W solar panel run a box fan?
Not on its own in Tennessee: even in the best month a 200 W panel puts back less than a typical box fan uses (0.80 kWh a day). It takes about 390 W to keep up all year, at 85% charging and 85% inverter efficiency. A panel alone can’t run it at night or under cloud; the battery does that.
What size battery do I need for a box fan on solar?
About 950 Wh to cover one day without sun (a day’s use ÷ 0.85 inverter efficiency, for a power station or lithium battery). Double it for lead-acid, which shouldn’t be run below half.
How many kWh does a box fan use a day?
About 0.80 kWh a day in the months you use it (about 120 days a year), based on 100 W for 8 hours a day, 120 days a year (96 kWh/yr). Your own use depends on the model and how you use it.
Sources and assumptions
- Solar output (kWh per kW of panels, by month): Global Solar Atlas 2.0, long-term averages to 2025 (data version 2.2.68, updated 2026-04-01), for crystalline-silicon panels facing south at the best fixed tilt, after typical system losses. Data obtained from the “Global Solar Atlas 2.0, a free, web-based application is developed and operated by the company Solargis s.r.o. on behalf of the World Bank Group, utilizing Solargis data, with funding provided by the Energy Sector Management Assistance Program (ESMAP). For additional information: https://globalsolaratlas.info” Licensed CC BY 4.0; we rounded and combined it as described here. Not affiliated with or endorsed by Solargis or the World Bank Group.
- State figure: population-weighted average of the state’s three largest cities (U.S. Census Bureau Vintage 2024 population estimates; coordinates from the 2020 Census Gazetteer). Hawaii and DC use one city.
- Cross-check: NASA POWER sunshine climatology (2001–2025), tilted with a standard isotropic-sky model × 0.80. States more than 12% apart were reviewed by hand; the gaps are explained on our methodology page.
- Home use: EIA Table 5A, 2024 average monthly residential kWh by state. Rates: EIA Electric Power Monthly, August 2026.
- Tax credit: IRS FAQ on the One, Big, Beautiful Bill (FS-2025-05, Aug. 21, 2025).
- Assumptions: 85% charging efficiency into a battery, 85% from battery to appliance, panel counts rounded up, off-grid sizing for the worst month.