Peak sun hours in Rhode Island
Rhode Island averages 4.1 peak sun hours a day across the year, 36th of the 50 states. At that figure a 400-watt panel produces about 1.26 kWh a day after real-world losses, and covering the 900 kWh average US bill takes about 24 panels. Providence, the state's biggest city, sits at 4.1 hours, close enough to the statewide figure to use either, though elevation and distance from water still move the number street by street.
modest sun: 4.1 of a possible ~6.5 hours
Panel counts for Rhode Island bills
Computed at Rhode Island's 4.1 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 | Rhode Island | System size | US average |
|---|---|---|---|
| 500 kWh/mo | 14 panels | 5.6 kW | 12 panels |
| 750 kWh/mo | 20 panels | 8 kW | 18 panels |
| 900 kWh/mo | 24 panels | 9.6 kW | 22 panels |
| 1,000 kWh/mo | 27 panels | 10.8 kW | 24 panels |
| 1,500 kWh/mo | 40 panels | 16 kW | 36 panels |
| 2,000 kWh/mo | 53 panels | 21.2 kW | 48 panels |
What 4.1 hours means in practice
Rhode Island runs 9% below the national solar average, 36th of 50 at 4.1 hours. That is workable sun, not bad sun: the 900 kWh bill takes 24 panels here versus 22 nationally, 2 more. Germany built the world's densest solar fleet on worse.
How a Rhode Island year is shaped
The 4.1-hour figure is an annual average, and no month is average. These are the twelve monthly means for Rhode Island from NASA's 2001-2020 solar climatology, each as a share of the state's own annual mean, with that share applied to the 4.1-hour planning figure. July and December are marked.
| Month | Share of the annual average | Peak sun hours (est.) |
|---|---|---|
| January | 47% | 1.9 |
| February | 69% | 2.8 |
| March | 96% | 3.9 |
| April | 125% | 5.1 |
| May | 140% | 5.7 |
| June | 152% | 6.2 |
| July | 154% | 6.3 |
| August | 138% | 5.7 |
| September | 112% | 4.6 |
| October | 75% | 3.1 |
| November | 52% | 2.1 |
| December | 39% | 1.6 |
Best to worst in Rhode Island is 4 to one: July at 154% of the annual average, December at 39%, 6.3 hours a day against 1.6. 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 Rhode Island 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 5.1 hours a day, so the productive half of the year starts earlier than most people expect.
Bills here are small, which changes the shape of the whole decision: EIA put the average Rhode Island household at 567 kWh a month in 2024, 34% under the national 863 and among the lowest in the country. 15 panels cover it across a year, and 39 would be needed to cover it from December sun alone, 2.6 times as many. A gap that wide is what pushes people here onto net metering rather than a battery bank.
One more limit worth stating: Rhode Island fits inside a single cell of the one-degree grid this seasonal data comes on, so the measurement cannot show any spread within the state at all. That is a resolution problem, not evidence that Rhode Island is uniform. Elevation and distance from the water move the local number here as they do everywhere.
What that sun is worth on a Rhode Island bill
| EIA, 2024 residential averages | Rhode Island | United States |
|---|---|---|
| Average home's monthly use | 567 kWh | 863 kWh |
| Price per kilowatt-hour | 28.65¢ | 16.48¢ |
| Average monthly bill | $162.40 | $142.26 |
| One 400W panel, a year's output | 461 kWh | 506 kWh |
| What that output displaces | $132 | $83 |
The rate matters more here than the sun does. Rhode Island residential power averaged 28.65¢ a kilowatt-hour in 2024, 74% over the national 16.48¢ and 5th highest of the fifty states, so a 400-watt panel offsets about $132 of electricity a year despite Rhode Island sitting 36th on sunlight. A cheap-power state would need most of another peak sun hour to match that.
Which is why the sun ranking undersells Rhode Island. It places 36th of fifty for sunlight and 3rd 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: West Virginia gets less sun (3.9 hours to Rhode Island's 4.1) and pays 15.07¢ against 28.65¢, so one panel is worth about $66 more a year in Rhode Island than in West Virginia.
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; 28.65¢ is every Rhode Island 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 Rhode Island?
About 24 400-watt panels (9.6 kW) for the 900 kWh a month an average US home uses, at Rhode Island's 4.1 peak sun hours. For the average Rhode Island home specifically, which EIA measured at 567 kWh a month in 2024, it is 15. Your own bill is the variable that matters, and the calculator takes any figure.
Is 4.1 peak sun hours good for solar?
It is below the 4.5-hour national average but far from disqualifying. Panel counts run about 10% 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 Rhode Island?
About $132. One 400-watt panel at Rhode Island's 4.1 peak sun hours makes roughly 461 kWh a year after the 0.77 derate, and Rhode Island residential electricity averaged 28.65¢ a kilowatt-hour in 2024 (EIA), which puts Rhode Island 3rd of the 50 states on this measure against 36th 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 Rhode Island?
Yes, by a factor of 4 here. NASA's 2001-2020 climatology puts Rhode Island's July at 154% of the annual average and December at 39%, so the 4.1-hour figure on this page is the midpoint of a curve running from roughly 6.3 hours a day down to 1.6. Grid-tied homes bank the summer surplus as credit; off-grid designs have to size for the trough, and in Rhode Island that means 39 panels for an average local bill instead of 15.