How much solar output drops in winter, region by region

By Emily CarterPublished October 27, 2026Data as of 2026-10-27: PVWatts® v8, typical-year weather

Solar panels in all 100 cities make less in winter than in summer, but the size of the drop varies widely. From December to February a Tampa roof makes 93% of what it makes from June to August; a Seattle roof makes 31% and an Anchorage roof 18%. By Census region, the South holds up best in winter and the Midwest drops furthest.

Four regions, four shapes

The chart shows the average month in each Census region. All four peak in late spring or summer and bottom out in December, but the shapes differ. The West has the highest summer, about 165 kWh per kW a month from May to July, and falls to 91.3 in December. The South has a much lower peak (143.0) but a December almost as high as the West's (89.5 against 91.3), so its year is the flattest.

The Midwest and the Northeast follow the same path at a lower level. In December their averages are 65.0 and 61.3 kWh per kW, less than half of their July figures. Measured as winter (December to February) over summer (June to August) output, the regions rank South 0.68, West 0.59, Northeast 0.55 and Midwest 0.53.

Division by division

The nine Census divisions split the regions further. The table gives each division's median winter ÷ summer ratio, where 1.00 would mean winter output as high as summer, and the median ratio between a city's best and weakest month.

The South Atlantic and Mountain divisions hold up best in winter, and the East North Central drops furthest. The Pacific median hides a split. Its three northern cities, Anchorage, Portland and Seattle, are the three most seasonal in the whole data set, while its eight Southern California cities make between 64% and 70% as much in winter as in summer, above the national median of 62%. That is why each city page shows its own monthly table.

Which month is best

July is the best month in 47 cities, May in 28, June in 15 and August in 8. Two Florida cities peak in spring: Miami in April and Orlando in March. December is the weakest month in 82 cities, January in 10 and February in 7, and Plano, TX bottoms out in November.

The February lows are all in Texas, Oklahoma, Louisiana and coastal Southern California (San Diego, Long Beach, Corpus Christi, Oklahoma City, New Orleans, San Antonio and Austin). In those cities the December figure is not the lowest of the winter. The month-by-month page lists the best and weakest city for each month.

The steadiest and the most seasonal cities

The median city makes 62% as much in winter as in summer. At one end, Tampa, FL makes 93%: its winter is nearly as productive as its summer. At the other, Seattle, WA makes 31% and Anchorage, AK only 18%. In Anchorage the best month makes 17.4× as much as the worst.

Being far south is not enough on its own. Honolulu, HI, the southernmost city on the list, has a winter ÷ summer ratio of 0.80, and five cities beat it, led by Tampa, Miami and Orlando. El Paso, TX, the sunniest city over the year, is also among the steadiest, at 0.80.

Winter ÷ summer output, December–February against June–August.

What the swing means for a single roof

A yearly total hides the seasons, so read the monthly table on the city page as well. Two cities can match over the year and still differ in winter. Tampa, FL and Oakland, CA make almost the same amount a year (1,568 and 1,582 kWh per kW), yet in December one makes 109.1 and the other 83.0. Their winter ÷ summer ratios are 0.93 and 0.53. The “most similar seasons” list on each city page pairs cities by the shape of their year, not just its size.

Tilt shifts the balance. A south-facing roof tilted to the city's latitude makes more in winter and less in summer than a 20° roof, and flat panels do the opposite; the direction guide has the numbers. The estimator shows the monthly bars for any layout, and comparing a northern and a southern city there makes the difference in winter easy to see.

Sources

• PVWatts® Calculator API v8, National Laboratory of the Rockies (NLR, formerly NREL): developer.nlr.gov. 600 model runs (100 cities × 6 layouts), retrieved 2026-10-27.
• Weather: NSRDB typical-meteorological-year data returned by PVWatts® (NSRDB PSM V3 GOES tmy-2020 3.2.0, NSRDB PSM V4 Polar tmy-2023 1.0.0).
• City list and locations: U.S. Census Bureau, Vintage 2024 Population Estimates for incorporated places (SUB-EST2024) and U.S. Census Bureau, 2024 Gazetteer Files - Places (census.gov).
• Every figure in this guide is computed by SunYieldMap from those model runs. Settings and limits are in the methodology.