Peak sun hours in Wisconsin
Wisconsin averages 4 peak sun hours a day across the year, 40th of the 50 states. At that figure a 400-watt panel produces about 1.23 kWh a day after real-world losses, and covering the 900 kWh average US bill takes about 25 panels. Milwaukee, the state's biggest city, sits at 4 hours, close enough to the statewide figure to use either, though elevation and distance from water still move the number street by street.
modest sun: 4 of a possible ~6.5 hours
Panel counts for Wisconsin bills
Computed at Wisconsin's 4 hours with 400W panels and the 0.77 derate; the US-average column shows what the same bill takes at 4.5 hours, so you can see what your state's sun is worth in hardware.
| Monthly usage | Wisconsin | System size | US average |
|---|---|---|---|
| 500 kWh/mo | 14 panels | 5.6 kW | 12 panels |
| 750 kWh/mo | 21 panels | 8.4 kW | 18 panels |
| 900 kWh/mo | 25 panels | 10 kW | 22 panels |
| 1,000 kWh/mo | 27 panels | 10.8 kW | 24 panels |
| 1,500 kWh/mo | 41 panels | 16.4 kW | 36 panels |
| 2,000 kWh/mo | 54 panels | 21.6 kW | 48 panels |
What 4 hours means in practice
Wisconsin runs 11% below the national solar average, 40th of 50 at 4 hours. That is workable sun, not bad sun: the 900 kWh bill takes 25 panels here versus 22 nationally, 3 more. Germany built the world's densest solar fleet on worse.
How a Wisconsin year is shaped
The 4-hour figure is an annual average, and no month is average. These are the twelve monthly means for Wisconsin from NASA's 2001-2020 solar climatology, each as a share of the state's own annual mean, with that share applied to the 4-hour planning figure. July and December are marked.
| Month | Share of the annual average | Peak sun hours (est.) |
|---|---|---|
| January | 44% | 1.8 |
| February | 72% | 2.9 |
| March | 100% | 4.0 |
| April | 122% | 4.9 |
| May | 144% | 5.8 |
| June | 159% | 6.4 |
| July | 164% | 6.6 |
| August | 139% | 5.5 |
| September | 108% | 4.3 |
| October | 69% | 2.8 |
| November | 44% | 1.8 |
| December | 32% | 1.3 |
Wisconsin's light is front-loaded into summer. July holds 164% of the annual average against December's 32%, 5.1 to one, and the four strongest months carry 51% of the year. Read across the table: 6.6 hours a day in July, about 1.3 in December. The annual average is honest arithmetic and thin planning, because most of the energy shows up in the months you need heating least.
Wisconsin beats its own annual average in 7 months of the twelve, March through September, and those months hold 78% of the year's sunlight. A long productive season like that is worth as much to an annual total as a high peak is, and it is the half of the picture the 4-hour headline figure cannot show.
Wisconsin homes are light users by national standards, 645 kWh a month on EIA's 2024 average against 863 nationally, 25% below. That is only 18 panels at the annual figure, which is why modest arrays go a long way here. Carrying the same house through December on its own would take 54, 3.0 times more.
Wisconsin is more uniform than most. The 16 grid cells sampled across the state span 10%, sunniest in the south and dimmest in the northwest, which scales to about 4.2 hours against 3.8. Enough to notice on a production estimate, not enough to change which system you buy. Milwaukee sits inside that band, not at the edge of it.
What that sun is worth on a Wisconsin bill
| EIA, 2024 residential averages | Wisconsin | United States |
|---|---|---|
| Average home's monthly use | 645 kWh | 863 kWh |
| Price per kilowatt-hour | 17.18¢ | 16.48¢ |
| Average monthly bill | $110.87 | $142.26 |
| One 400W panel, a year's output | 450 kWh | 506 kWh |
| What that output displaces | $77 | $83 |
At 17.18¢ a kilowatt-hour Wisconsin sits 4% above the national 16.48¢, 15th of the fifty states on price. One 400-watt panel offsets roughly $77 of Wisconsin power a year. Mid-table on rates means the project lives or dies on the quote and the net-metering terms rather than on either the sun or the tariff.
Which is why the sun ranking undersells Wisconsin. It places 40th of fifty for sunlight and 25th for what a panel actually earns, a jump of 15 places, and the second number is the one that shows up on a bill. Compare it with a state that gets similar sun: Rhode Island gets more sun (4.1 hours to Wisconsin's 4) and pays 28.65¢ against 17.18¢, so one panel is worth about $55 less a year in Wisconsin than in Rhode Island.
Two warnings on those dollar figures. They are displaced electricity and nothing else: no install cost, no incentive, no financing, and no assumption about how your utility settles a surplus, which is the single biggest unknown in the sum. And a state average hides the utility you are actually on; 17.18¢ is every Wisconsin residential customer averaged together, and neighbouring territories can differ by more than the gap between two states in the ranking.
Getting a number for your address
For a location-exact figure, run your address through NREL's free PVWatts; it uses measured weather for your grid cell and will also model roof tilt and direction, which statewide numbers cannot. Then compare its annual kWh against a quote's promise before you sign anything.
Questions people ask
How many solar panels do I need in Wisconsin?
About 25 400-watt panels (10 kW) for the 900 kWh a month an average US home uses, at Wisconsin's 4 peak sun hours. For the average Wisconsin home specifically, which EIA measured at 645 kWh a month in 2024, it is 18. Your own bill is the variable that matters, and the calculator takes any figure.
Is 4 peak sun hours good for solar?
It is below the 4.5-hour national average but far from disqualifying. Panel counts run about 13% higher here for the same bill, and the December trough measured above deserves respect in any off-grid plan. Grid-tied systems ride through it on net metering.
How much is one solar panel worth a year in Wisconsin?
About $77. One 400-watt panel at Wisconsin's 4 peak sun hours makes roughly 450 kWh a year after the 0.77 derate, and Wisconsin residential electricity averaged 17.18¢ a kilowatt-hour in 2024 (EIA), which puts Wisconsin 25th of the 50 states on this measure against 40th on sunlight alone. That figure is displaced electricity only. It says nothing about install cost, incentives, or how your utility settles a surplus.
Do peak sun hours change with the seasons in Wisconsin?
Yes, by a factor of 5.1 here. NASA's 2001-2020 climatology puts Wisconsin's July at 164% of the annual average and December at 32%, so the 4-hour figure on this page is the midpoint of a curve running from roughly 6.6 hours a day down to 1.3. Grid-tied homes bank the summer surplus as credit; off-grid designs have to size for the trough, and in Wisconsin that means 54 panels for an average local bill instead of 18.