Peak sun hours in Maine
Maine averages 3.9 peak sun hours a day across the year, 41st of the 50 states. At that figure a 400-watt panel produces about 1.20 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, runs slightly ahead of the statewide figure at 4 hours; treat 3.9 as the midpoint of a real spread rather than a local reading.
modest sun: 3.9 of a possible ~6.5 hours
Panel counts for Maine bills
Computed at Maine's 3.9 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 | Maine | 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 | 28 panels | 11.2 kW | 24 panels |
| 1,500 kWh/mo | 42 panels | 16.8 kW | 36 panels |
| 2,000 kWh/mo | 55 panels | 22 kW | 48 panels |
What 3.9 hours means in practice
Maine runs 13% below the national solar average, 41st of 50 at 3.9 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 Maine year is shaped
The 3.9-hour figure is an annual average, and no month is average. These are the twelve monthly means for Maine from NASA's 2001-2020 solar climatology, each as a share of the state's own annual mean, with that share applied to the 3.9-hour planning figure. July and December are marked.
| Month | Share of the annual average | Peak sun hours (est.) |
|---|---|---|
| January | 43% | 1.7 |
| February | 67% | 2.6 |
| March | 100% | 3.9 |
| April | 128% | 5.0 |
| May | 145% | 5.6 |
| June | 156% | 6.1 |
| July | 159% | 6.2 |
| August | 142% | 5.5 |
| September | 113% | 4.4 |
| October | 70% | 2.7 |
| November | 44% | 1.7 |
| December | 33% | 1.3 |
Maine's light is front-loaded into summer. July holds 159% of the annual average against December's 33%, 4.9 to one, and the four strongest months carry 50% of the year. Read across the table: 6.2 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.
Maine beats its own annual average in 7 months of the twelve, March through September, and those months hold 79% 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 3.9-hour headline figure cannot show.
Bills here are small, which changes the shape of the whole decision: EIA put the average Maine household at 550 kWh a month in 2024, 36% under the national 863 and among the lowest in the country. 16 panels cover it across a year, and 47 would be needed to cover it from December sun alone, 2.9 times as many. A gap that wide is what pushes people here onto net metering rather than a battery bank.
Maine is more uniform than most. The 9 grid cells sampled across the state span 10%, sunniest in the southwest and dimmest in the west, which scales to about 4.1 hours against 3.7. Enough to notice on a production estimate, not enough to change which system you buy. Portland sits inside that band, not at the edge of it.
What that sun is worth on a Maine bill
| EIA, 2024 residential averages | Maine | United States |
|---|---|---|
| Average home's monthly use | 550 kWh | 863 kWh |
| Price per kilowatt-hour | 24.29¢ | 16.48¢ |
| Average monthly bill | $133.60 | $142.26 |
| One 400W panel, a year's output | 438 kWh | 506 kWh |
| What that output displaces | $106 | $83 |
Maine pays 24.29¢ a kilowatt-hour, 8th highest in the country and 47% over the national 16.48¢. A single 400-watt panel therefore displaces about $106 of electricity a year here. Prices above the national line do more for a solar case than an extra half hour of sun does, because the sun sets the numerator and the rate sets what it is worth.
Which is why the sun ranking undersells Maine. It places 41st of fifty for sunlight and 8th for what a panel actually earns, a jump of 33 places, and the second number is the one that shows up on a bill. Compare it with a state that gets similar sun: Washington gets less sun (3.8 hours to Maine's 3.9) and pays 11.9¢ against 24.29¢, so one panel is worth about $56 more a year in Maine than in Washington.
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; 24.29¢ is every Maine 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 Maine?
About 25 400-watt panels (10 kW) for the 900 kWh a month an average US home uses, at Maine's 3.9 peak sun hours. For the average Maine home specifically, which EIA measured at 550 kWh a month in 2024, it is 16. Your own bill is the variable that matters, and the calculator takes any figure.
Is 3.9 peak sun hours good for solar?
It is below the 4.5-hour national average but far from disqualifying. Panel counts run about 15% 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 Maine?
About $106. One 400-watt panel at Maine's 3.9 peak sun hours makes roughly 438 kWh a year after the 0.77 derate, and Maine residential electricity averaged 24.29¢ a kilowatt-hour in 2024 (EIA), which puts Maine 8th of the 50 states on this measure against 41st 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 Maine?
Yes, by a factor of 4.9 here. NASA's 2001-2020 climatology puts Maine's July at 159% of the annual average and December at 33%, so the 3.9-hour figure on this page is the midpoint of a curve running from roughly 6.2 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 Maine that means 47 panels for an average local bill instead of 16.