Peak sun hours in Iowa
Iowa averages 4.4 peak sun hours a day across the year, 24th of the 50 states. At that figure a 400-watt panel produces about 1.36 kWh a day after real-world losses, and covering the 900 kWh average US bill takes about 22 panels. Des Moines, the state's biggest city, runs slightly ahead of the statewide figure at 4.5 hours; treat 4.4 as the midpoint of a real spread rather than a local reading.
solid mid-pack sun: 4.4 of a possible ~6.5 hours
Panel counts for Iowa bills
Computed at Iowa's 4.4 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 | Iowa | System size | US average |
|---|---|---|---|
| 500 kWh/mo | 13 panels | 5.2 kW | 12 panels |
| 750 kWh/mo | 19 panels | 7.6 kW | 18 panels |
| 900 kWh/mo | 22 panels | 8.8 kW | 22 panels |
| 1,000 kWh/mo | 25 panels | 10 kW | 24 panels |
| 1,500 kWh/mo | 37 panels | 14.8 kW | 36 panels |
| 2,000 kWh/mo | 49 panels | 19.6 kW | 48 panels |
What 4.4 hours means in practice
Iowa is mid-pack American sun: 24th of 50 at 4.4 peak sun hours, within 2% of the national average. The 900 kWh average bill lands at 22 panels, same as the US-average count. At this tier the resource neither makes nor breaks the project, which is what the rate and the seasonal spread below are for.
How a Iowa year is shaped
The 4.4-hour figure is an annual average, and no month is average. These are the twelve monthly means for Iowa from NASA's 2001-2020 solar climatology, each as a share of the state's own annual mean, with that share applied to the 4.4-hour planning figure. July and December are marked.
| Month | Share of the annual average | Peak sun hours (est.) |
|---|---|---|
| January | 48% | 2.1 |
| February | 74% | 3.3 |
| March | 95% | 4.2 |
| April | 119% | 5.2 |
| May | 139% | 6.1 |
| June | 154% | 6.8 |
| July | 159% | 7.0 |
| August | 137% | 6.0 |
| September | 110% | 4.8 |
| October | 75% | 3.3 |
| November | 51% | 2.3 |
| December | 39% | 1.7 |
Best to worst in Iowa is 4.1 to one: July at 159% of the annual average, December at 39%, 7.0 hours a day against 1.7. Four months hold 49% of the year's light. A grid-tied array absorbs that on net metering; a battery bank has to be sized for the December end of it.
Half the Iowa calendar sits above the annual average and half below: April through September are the six months that beat it, carrying 68% of the year's light. April is already worth about 5.2 hours a day, so the productive half of the year starts earlier than most people expect.
Iowa's average home used 832 kWh a month in 2024 by EIA's count, within a few percent of the national 863, so the national panel counts on this page transfer here better than they do in most states. That average bill needs 21 panels across the year and 52 to be carried by December sun alone, a factor of 2.5.
Iowa is more uniform than most. The 14 grid cells sampled across the state span 6%, sunniest in the southwest and dimmest in the northeast, which scales to about 4.5 hours against 4.3. Enough to notice on a production estimate, not enough to change which system you buy. Des Moines sits inside that band, not at the edge of it.
What that sun is worth on a Iowa bill
| EIA, 2024 residential averages | Iowa | United States |
|---|---|---|
| Average home's monthly use | 832 kWh | 863 kWh |
| Price per kilowatt-hour | 13.4¢ | 16.48¢ |
| Average monthly bill | $111.54 | $142.26 |
| One 400W panel, a year's output | 495 kWh | 506 kWh |
| What that output displaces | $66 | $83 |
Cheap power cuts the other way. Iowa residential electricity averaged 13.4¢ a kilowatt-hour in 2024, 19% under the national 16.48¢ and 16th cheapest in the country, so the same panel that offsets $83 a year at national rates offsets about $66 here. Nothing is wrong with the sun. There is just less money in each kilowatt-hour it makes.
Here the sun ranking flatters Iowa. 24th of fifty for sunlight, but only 39th for what a panel earns in a year, a drop of 15 places, and the reason is entirely the price of the electricity being replaced. Alabama gets more sun (4.6 hours to Iowa's 4.4) and pays 15.18¢ against 13.4¢, so one panel is worth about $12 less a year in Iowa than in Alabama.
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; 13.4¢ is every Iowa 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 Iowa?
About 22 400-watt panels (8.8 kW) for the 900 kWh a month an average US home uses, at Iowa's 4.4 peak sun hours. For the average Iowa home specifically, which EIA measured at 832 kWh a month in 2024, it is 21. Your own bill is the variable that matters, and the calculator takes any figure.
Is 4.4 peak sun hours good for solar?
It is solidly workable. Iowa sits near the national average of 4.5 hours, so panel counts here match the US-typical figures, and project economics turn on your utility's rates and net-metering terms rather than on the sun.
How much is one solar panel worth a year in Iowa?
About $66. One 400-watt panel at Iowa's 4.4 peak sun hours makes roughly 495 kWh a year after the 0.77 derate, and Iowa residential electricity averaged 13.4¢ a kilowatt-hour in 2024 (EIA), which puts Iowa 39th of the 50 states on this measure against 24th 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 Iowa?
Yes, by a factor of 4.1 here. NASA's 2001-2020 climatology puts Iowa's July at 159% of the annual average and December at 39%, so the 4.4-hour figure on this page is the midpoint of a curve running from roughly 7.0 hours a day down to 1.7. Grid-tied homes bank the summer surplus as credit; off-grid designs have to size for the trough, and in Iowa that means 52 panels for an average local bill instead of 21.