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, sits at 6.6 hours, close to the statewide figure, though microclimates and elevation still move the local number.
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.
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. Your bill is the variable that matters: the table on this page covers 500 to 2,000 kWh, 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.
Do peak sun hours change with the seasons in Arizona?
Yes, everywhere: the figure on this page is the annual average of a curve that peaks in June and bottoms out in December. In Arizona the swing is meaningful but manageable; summer typically runs half again the annual figure and December two-thirds or less of it. Grid-tied homes bank summer overproduction as credit; off-grid designs must size for the trough, not the average.