Peak sun hours in Oregon
Oregon averages 4 peak sun hours a day across the year, 39th 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. Portland, the state's biggest city, sits a little under the statewide figure at 3.8 hours, so 4 is the midpoint of a spread that leans away from the largest population centre.
modest sun: 4 of a possible ~6.5 hours
Panel counts for Oregon bills
Computed at Oregon'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 | Oregon | 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
Oregon runs 11% below the national solar average, 39th 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 Oregon year is shaped
The 4-hour figure is an annual average, and no month is average. These are the twelve monthly means for Oregon 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 | 37% | 1.5 |
| February | 58% | 2.3 |
| March | 85% | 3.4 |
| April | 118% | 4.7 |
| May | 144% | 5.8 |
| June | 165% | 6.6 |
| July | 175% | 7.0 |
| August | 151% | 6.0 |
| September | 116% | 4.6 |
| October | 76% | 3.0 |
| November | 44% | 1.7 |
| December | 30% | 1.2 |
Oregon runs a short, hard solar year. July reaches 175% of the annual average and December falls to 30%, 5.8 to one, with 53% of the light arriving in four months. In hours that is 7.0 a day at the July top against roughly 1.2 in December. Sizing a Oregon array off the annual figure alone is fine on the grid and badly wrong off it.
Half the Oregon calendar sits above the annual average and half below: April through September are the six months that beat it, carrying 72% of the year's light. April is already worth about 4.7 hours a day, so the productive half of the year starts earlier than most people expect.
Oregon's average home used 882 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 24 panels across the year and 79 to be carried by December sun alone, a factor of 3.3.
Oregon is one of the states where a statewide number does the most damage: it has the 2nd widest internal spread of the fifty. Across the 20 grid cells sampled here the southwest runs 29% sunnier than the northwest. Held against the 4-hour statewide figure that is roughly 4.6 hours at one end and 3.4 at the other, which is the difference between two quite different quotes. Nobody should size a Oregon roof off the state average without checking which end of the state it sits on.
What that sun is worth on a Oregon bill
| EIA, 2024 residential averages | Oregon | United States |
|---|---|---|
| Average home's monthly use | 882 kWh | 863 kWh |
| Price per kilowatt-hour | 14.7¢ | 16.48¢ |
| Average monthly bill | $129.62 | $142.26 |
| One 400W panel, a year's output | 450 kWh | 506 kWh |
| What that output displaces | $66 | $83 |
Cheap power cuts the other way. Oregon residential electricity averaged 14.7¢ a kilowatt-hour in 2024, 11% under the national 16.48¢ and 24th 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.
Oregon lands in much the same place on both rankings, 39th for sun and 40th for what a panel earns, so its position in the sun table is a fair guide to its position on value. That is not automatic. Rhode Island gets more sun (4.1 hours to Oregon's 4) and pays 28.65¢ against 14.7¢, so one panel is worth about $66 less a year in Oregon 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; 14.7¢ is every Oregon 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 Oregon?
About 25 400-watt panels (10 kW) for the 900 kWh a month an average US home uses, at Oregon's 4 peak sun hours. For the average Oregon home specifically, which EIA measured at 882 kWh a month in 2024, it is 24. 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 Oregon?
About $66. One 400-watt panel at Oregon's 4 peak sun hours makes roughly 450 kWh a year after the 0.77 derate, and Oregon residential electricity averaged 14.7¢ a kilowatt-hour in 2024 (EIA), which puts Oregon 40th of the 50 states on this measure against 39th 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 Oregon?
Yes, by a factor of 5.8 here. NASA's 2001-2020 climatology puts Oregon's July at 175% of the annual average and December at 30%, so the 4-hour figure on this page is the midpoint of a curve running from roughly 7.0 hours a day down to 1.2. Grid-tied homes bank the summer surplus as credit; off-grid designs have to size for the trough, and in Oregon that means 79 panels for an average local bill instead of 24.