What are Peak Sun Hours?
- Katie Burgess
- 3 days ago
- 2 min read
The performance of your solar panels aboard will vary on a number of factors including shading, temperature, location, dirt, time of year etc but there are some numbers you can look at to get an idea of what your panels should be producing.
Panels are rated by their wattage (eg 100W or 470W) but this is under Standard Test Conditions (STC) and so a 100W panel for example does not give you 100W all the time. The 100W panel will wake up in the morning and give you 30W, 50W, 75W and then hopefully a few hours in the middle of the day at 100W and then slow down production into the afternoon. As an average this works out to be 4.5hrs to 5hrs at full rating (AKA Peak Sun Hours.) So a 100W panel will yield 450Wh-500Wh over the course of a day (100W x 4.5h-5h)
To dig deeper into this and get a more accurate number you can look at your location in the country and then see how much better you will do in the summer months v. winter months.
STATE | AVERAGE SUN HRS | SUMMER AVERAGE | WINTER AVERAGE |
Alabama | 4.32 | 4.69 | 3.37 |
Alaska | 2.99 | 3.87 | 1.78 |
Arizona | 6.57 | 7.42 | 6.01 |
Arkansas | 4.69 | 5.29 | 3.88 |
California | 5.38 | 6.19 | 3.42 |
Colorado | 4.87 | 5.72 | 4.44 |
Connecticut | 3.84 | 4.27 | 2.99 |
Delaware | 4.23 | 4.69 | 3.37 |
Florida | 5.67 | 6.16 | 5.26 |
Georgia | 4.74 | 5.16 | 4.09 |
Hawaii | 6.02 | 6.71 | 5.59 |
Idaho | 4.92 | 5.83 | 3.33 |
Illinois | 3.14 | 4.08 | 2.47 |
Indiana | 4.21 | 5.02 | 2.55 |
Iowa | 4.55 | 5.05 | 2.99 |
Kansas | 5.79 | 6.14 | 5.28 |
Kentucky | 4.94 | 5.97 | 3.6 |
Louisiana | 4.92 | 5.71 | 3.63 |
Maine | 4.51 | 5.2 | 3.56 |
Maryland | 4.47 | 4.71 | 3.84 |
Massachusetts | 3.84 | 4.27 | 2.99 |
Michigan | 4 | 4.71 | 2.7 |
Minnesota | 4.53 | 5.43 | 3.53 |
Mississippi | 4.44 | 4.86 | 3.64 |
Missouri | 4.73 | 5.5 | 3.97 |
Montana | 4.93 | 5.7 | 3.66 |
Nebraska | 4.79 | 5.4 | 4.38 |
Nevada | 6.41 | 7.13 | 5.83 |
New Hampshire | 4.61 | 5.3 | 3.66 |
New Jersey | 4.21 | 4.76 | 3.2 |
New Mexico | 6.77 | 7.16 | 6.21 |
New York | 3.79 | 4.57 | 2.29 |
North Carolina | 4.71 | 5.05 | 4.71 |
North Dakota | 5.01 | 5.48 | 3.97 |
Ohio | 4.15 | 5.26 | 2.66 |
Oklahoma | 5.59 | 6.26 | 4.98 |
Oregan | 4.03 | 5.71 | 1.9 |
Pennsylvania | 3.91 | 4.44 | 2.78 |
Rhode Island | 4.23 | 4.69 | 3.58 |
South Carolina | 5.06 | 5.72 | 4.23 |
South Dakota | 5.23 | 5.91 | 4.56 |
Tennessee | 4.45 | 5.2 | 3.14 |
Texas | 4.92 | 5.49 | 4.42 |
Utah | 5.26 | 6.09 | 3.78 |
Vermont | 4.13 | 5.35 | 3.77 |
Virginia | 4.13 | 4.5 | 3.37 |
Washington | 3.57 | 4.83 | 2.6 |
West Virginia | 3.56 | 4.12 | 2.47 |
Wisconsin | 4.29 | 4.85 | 3.28 |
Wyoming | 6.06 | 6.81 | 5.5 |
Source: NREL
Looking at the table above:
A boat with 500W of solar sailing in Annapolis in the summer could expect to yield 2,355Wh (500W x 4.71h)
A boat with 500W of solar sailing in Miami in the summer could expect to yield 3,080Wh (500W x 6.16h)
That's a 30% greater yield by a boat in Florida with the same amount of solar aboard as the one sailing in Annapolis. There are a lot of other variables, not just location, but it gives you a good indication of what to expect.