Solar · Montana
How many solar panels do I need in Montana?
For the average Montana home, which uses 852 kWh a month (EIA, 2024), about 18 × 400 W solar panels (6.93 kW) facing south at the best tilt. One kW of panels in Montana makes about 1,475 kWh a year, 5.5 kWh a day in July and 2.2 in December, the 25th sunniest of 51.
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Your electricity use
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Solar output by month in Montana
Output falls to 41% of the July level in December. Grid-tied homes are sized on the year; anything off-grid has to be sized for December.
| Month | kWh per kW | Per day | 200 W panel, Wh/day into a battery |
|---|---|---|---|
| January | 79 | 2.55 | 433 |
| February | 93 | 3.31 | 563 |
| March | 129 | 4.15 | 706 |
| April | 138 | 4.60 | 782 |
| May | 149 | 4.81 | 818 |
| June | 152 | 5.07 | 862 |
| July | 170 | 5.49 | 934 |
| August | 160 | 5.15 | 875 |
| September | 139 | 4.63 | 787 |
| October | 113 | 3.66 | 621 |
| November | 84 | 2.80 | 476 |
| December | 69 | 2.24 | 381 |
Charging a power station in Montana
A 200 W panel propped up facing south refills a 1,000 Wh power station in about 1.1 days in July and 2.6 days in December. To refill it in one day you’d need about 220 W of panels in July and 530 W in December. Check your station and panel →
A balcony or plug-in panel in Montana
A 400 W panel hanging upright on a south-facing railing makes about 411 kWh a year, worth about $64.03 at Montana’s average rate (15.57¢/kWh, August 2026), if you use the power as it’s made. Shade and the rules where you live matter more than anything here. Try your kit →
The rules in Montana: We found no state law on plug-in solar in Montana as of November 5, 2026; ask your utility. Every state we track →
Across Montana
Montana’s figure is the population-weighted average of Billings, Missoula and Great Falls, its three largest cities; across them, a kW makes 1,397 to 1,511 kWh a year.
| City | Population (2024) | kWh per kW a year |
|---|---|---|
| Billings | 121,483 | 1,511 |
| Missoula | 78,204 | 1,397 |
| Great Falls | 60,013 | 1,503 |
Cross-check: an estimate from NASA POWER sunshine came out at 1,334 kWh per kW, 11% below the Global Solar Atlas figure. Within our 12% threshold.
Electricity rates and appliance costs in Montana →
FAQ
How many solar panels do I need in Montana?
For the average Montana home, which uses 852 kWh a month (EIA, 2024), about 18 × 400 W solar panels (6.93 kW) facing south at the best tilt. One kW of panels in Montana makes about 1,475 kWh a year, 5.5 kWh a day in July and 2.2 in December, the 25th sunniest of 51.
How much does a solar panel produce in Montana?
A 400 W panel facing south at the best tilt makes about 590 kWh a year in Montana: about 68 kWh in July and 28 kWh in December (Global Solar Atlas).
How long does a 200 W solar panel take to charge a 1,000 Wh power station in Montana?
About 1.1 days in July and 2.6 days in December, propped up facing south, at 85% charging efficiency. Lying flat, about 5.4 days in December.
How many solar panels for the U.S. average home in Montana?
The U.S. average home uses 863 kWh a month (EIA, 2024). In Montana that takes about 7.02 kW: 18 × 400 W panels.
Is there still a federal solar tax credit?
Not under the residential credit for systems installed after 2025: the IRS says the section 25D credit will not be allowed for any expenditures made after December 31, 2025, and an expenditure counts as made when installation is completed.
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.