Peak sun hours in Arizona
Arizona averages 6.5 peak sun hours a day across the year, 1st of the 50 states. At that figure a 400-watt panel produces about 2.00 kWh a day after real-world losses, and covering the 900 kWh average US bill takes about 15 panels. Phoenix, the state's biggest city, runs slightly ahead of the statewide figure at 6.6 hours; treat 6.5 as the midpoint of a real spread rather than a local reading.
desert-grade sun: 6.5 of a possible ~6.5 hours
Panel counts for Arizona bills
Computed at Arizona's 6.5 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 | Arizona | System size | US average |
|---|---|---|---|
| 500 kWh/mo | 9 panels | 3.6 kW | 12 panels |
| 750 kWh/mo | 13 panels | 5.2 kW | 18 panels |
| 900 kWh/mo | 15 panels | 6 kW | 22 panels |
| 1,000 kWh/mo | 17 panels | 6.8 kW | 24 panels |
| 1,500 kWh/mo | 25 panels | 10 kW | 36 panels |
| 2,000 kWh/mo | 33 panels | 13.2 kW | 48 panels |
What 6.5 hours means in practice
Arizona ranks 1st of the 50 states for solar resource, and the number shows up directly in system size: the 900 kWh average bill needs 15 panels here against 22 for the country as a whole, 7 fewer panels doing the same job. Sun this strong (44% above the US average) also means heat, and heat is the quiet tax on desert solar: panels lose output as cells warm, which is part of why we derate rated watts by 23% before publishing any number. Even after that haircut, this is the cheapest sunlight in the country per panel installed.
How a Arizona year is shaped
The 6.5-hour figure is an annual average, and no month is average. These are the twelve monthly means for Arizona from NASA's 2001-2020 solar climatology, each as a share of the state's own annual mean, with that share applied to the 6.5-hour planning figure. June and December are marked.
| Month | Share of the annual average | Peak sun hours (est.) |
|---|---|---|
| January | 59% | 3.8 |
| February | 76% | 4.9 |
| March | 102% | 6.6 |
| April | 126% | 8.2 |
| May | 140% | 9.1 |
| June | 146% | 9.5 |
| July | 124% | 8.1 |
| August | 116% | 7.5 |
| September | 105% | 6.8 |
| October | 87% | 5.6 |
| November | 66% | 4.3 |
| December | 53% | 3.5 |
The gap between Arizona's best month and its worst is 2.8 to one: June at 146% of the annual average, December at 53%, or about 9.5 hours a day against 3.5. Four months carry 45% of the year's light. Note the July step down to 124%. That is the summer storm cycle, not a weaker sun. A grid-tied system rides that out on net metering without anyone noticing.
Arizona beats its own annual average in 7 months of the twelve, March through September, and those months hold 72% 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 6.5-hour headline figure cannot show.
Set that against what Arizona homes actually draw. EIA measured 1,075 kWh a month for the average household here in 2024, 25% above the US figure, which is 18 panels at the annual average sun. Hold the same house to a December and the count goes to 34, 1.9 times higher. Net metering is what makes the first number the one that matters.
Arizona is more uniform than most. The 20 grid cells sampled across the state span 8%, sunniest in the southwest and dimmest in the northwest, which scales to about 6.8 hours against 6.2. Enough to notice on a production estimate, not enough to change which system you buy. Phoenix sits inside that band, not at the edge of it.
What that sun is worth on a Arizona bill
| EIA, 2024 residential averages | Arizona | United States |
|---|---|---|
| Average home's monthly use | 1,075 kWh | 863 kWh |
| Price per kilowatt-hour | 14.91¢ | 16.48¢ |
| Average monthly bill | $160.24 | $142.26 |
| One 400W panel, a year's output | 731 kWh | 506 kWh |
| What that output displaces | $109 | $83 |
Cheap power cuts the other way. Arizona residential electricity averaged 14.91¢ a kilowatt-hour in 2024, 10% under the national 16.48¢ and 26th cheapest in the country, so the same panel that offsets $83 a year at national rates offsets about $109 here. Nothing is wrong with the sun. There is just less money in each kilowatt-hour it makes.
Arizona ranks 1st of fifty for sun but 6th for what a panel is worth, 5 places lower, because the power it displaces is cheap. New Mexico gets less sun (6.4 hours to Arizona's 6.5) and pays 14.2¢ against 14.91¢, so one panel is worth about $7 more a year in Arizona than in New Mexico.
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; 14.91¢ is every Arizona 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 Arizona?
About 15 400-watt panels (6 kW) for the 900 kWh a month an average US home uses, at Arizona's 6.5 peak sun hours. For the average Arizona home specifically, which EIA measured at 1,075 kWh a month in 2024, it is 18. Your own bill is the variable that matters, and the calculator takes any figure.
Is 6.5 peak sun hours good for solar?
Yes, comfortably. Arizona ranks 1st of the 50 states, 44% above the national average, which means fewer panels per kWh of bill than almost anywhere else in the country.
How much is one solar panel worth a year in Arizona?
About $109. One 400-watt panel at Arizona's 6.5 peak sun hours makes roughly 731 kWh a year after the 0.77 derate, and Arizona residential electricity averaged 14.91¢ a kilowatt-hour in 2024 (EIA), which puts Arizona 6th of the 50 states on this measure against 1st 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 Arizona?
Yes, by a factor of 2.8 here. NASA's 2001-2020 climatology puts Arizona's June at 146% of the annual average and December at 53%, so the 6.5-hour figure on this page is the midpoint of a curve running from roughly 9.5 hours a day down to 3.5. Grid-tied homes bank the summer surplus as credit; off-grid designs have to size for the trough, and in Arizona that means 34 panels for an average local bill instead of 18.