Peak Sun Hours Reference
Peak sun hours (PSH) is the single most useful number for sizing a solar system. This page lists annual average, winter low and summer high values for 25 European cities, all 50 US states and 8 major world cities. Use the annual figure for grid-tied production estimates, the winter figure when sizing for off-grid autonomy. Values are typical multi-year averages calibrated to PVGIS (Europe) and the NREL National Solar Radiation Database (United States); for site-specific design, run your exact coordinates through PVGIS or PVWatts.
Last updated: May 2026
What peak sun hours means
One peak sun hour equals one hour of solar irradiance at 1,000 W/m², the standard test condition used to rate every solar panel. PSH for a location is not the count of daylight hours, it is the equivalent number of full-rated hours per day once you compress all the weaker morning, evening and cloudy moments into the reference brightness. A site at 5 PSH does not get five sunny hours and nineteen dark ones; it gets twelve to fifteen daylight hours whose total irradiation, summed and divided by 1,000 W/m², equals five hours at full sun. That is why a 400 W panel in a 5 PSH location produces about 2 kWh per day, not 2.4 or 2.8.
The headline formula is short: daily kWh ≈ panel kW × PSH × system efficiency. System efficiency is typically 0.75 to 0.85 once you account for inverter losses, wiring, temperature and soiling. PSH is the only term that varies by where you live, so it is the input the tables below provide. Latitude, climate and tilt all influence the number; the values shown assume a south-facing array (north-facing in the southern hemisphere) tilted near latitude angle, which is the typical residential install.
Europe peak sun hours
25 cities from Nordic to Mediterranean. Source basis: PVGIS multi-year averages for south-facing fixed mount at typical residential tilt. Latitude shown to support tilt decisions.
| City | Latitude | Annual avg PSH | Winter low | Summer high | Notes |
|---|---|---|---|---|---|
| Tromsø, Norway | 69.6° N | 1.8 | 0.0 | 5.5 | Polar night December and January |
| Oslo, Norway | 59.9° N | 2.7 | 0.4 | 5.5 | Cold clear winters help slightly |
| Stockholm, Sweden | 59.3° N | 2.7 | 0.4 | 5.6 | Strong seasonal swing |
| Helsinki, Finland | 60.2° N | 2.7 | 0.3 | 5.7 | Long winter near zero |
| Copenhagen, Denmark | 55.7° N | 2.8 | 0.6 | 5.3 | Cloud cover heavy in winter |
| London, United Kingdom | 51.5° N | 2.8 | 0.9 | 4.9 | Diffuse light most of the year |
| Dublin, Ireland | 53.3° N | 2.6 | 0.7 | 4.7 | Persistent overcast limits summer |
| Amsterdam, Netherlands | 52.4° N | 2.8 | 0.9 | 5.0 | Coastal cloud dominant |
| Brussels, Belgium | 50.9° N | 2.8 | 0.9 | 5.0 | Similar profile to Netherlands |
| Berlin, Germany | 52.5° N | 2.9 | 0.9 | 5.3 | Continental, clearer than coast |
| Munich, Germany | 48.1° N | 3.2 | 1.2 | 5.5 | Alpine foreland, sunnier than north |
| Warsaw, Poland | 52.2° N | 3.0 | 0.9 | 5.4 | Cold winters, decent summers |
| Prague, Czech Republic | 50.1° N | 3.0 | 0.9 | 5.4 | Similar to central Germany |
| Vienna, Austria | 48.2° N | 3.2 | 1.1 | 5.6 | Pannonian basin, sunnier exposure |
| Zurich, Switzerland | 47.4° N | 3.3 | 1.1 | 5.7 | Foehn-influenced, variable |
| Paris, France | 48.9° N | 3.2 | 1.1 | 5.5 | Average central-European profile |
| Lyon, France | 45.8° N | 3.7 | 1.4 | 6.0 | Rhône valley, strong summers |
| Marseille, France | 43.3° N | 4.6 | 2.2 | 6.7 | Mediterranean, mistral-cleared skies |
| Madrid, Spain | 40.4° N | 4.9 | 2.5 | 7.0 | High plateau, dry, cold winters |
| Barcelona, Spain | 41.4° N | 4.5 | 2.3 | 6.5 | Coastal Mediterranean |
| Seville, Spain | 37.4° N | 5.2 | 2.9 | 7.2 | Andalusian, among highest in EU |
| Lisbon, Portugal | 38.7° N | 4.9 | 2.6 | 6.9 | Atlantic coast, mild winters |
| Milan, Italy | 45.5° N | 3.7 | 1.4 | 6.0 | Po valley winter fog |
| Rome, Italy | 41.9° N | 4.5 | 2.2 | 6.7 | Strong Mediterranean summer |
| Athens, Greece | 37.9° N | 5.1 | 2.7 | 7.2 | Aegean, very high summer |
United States peak sun hours
All 50 states, alphabetical. Source basis: NREL National Solar Radiation Database (NSRDB) multi-year averages for south-facing fixed mount at typical residential tilt. The state's largest or capital city is shown as the representative point; actual values vary across each state, especially in elevation-rich and coast-versus-interior states.
| State (city) | Latitude | Annual avg PSH | Winter low | Summer high | Notes |
|---|---|---|---|---|---|
| Alabama (Birmingham) | 33.5° N | 4.6 | 2.7 | 6.0 | Humid subtropical |
| Alaska (Anchorage) | 61.2° N | 2.6 | 0.2 | 6.0 | Extreme seasonal swing; midnight sun summer |
| Arizona (Phoenix) | 33.4° N | 6.6 | 4.5 | 8.0 | Among highest in the world |
| Arkansas (Little Rock) | 34.7° N | 4.7 | 2.9 | 6.1 | South-central US average |
| California (Los Angeles) | 34.1° N | 5.5 | 3.5 | 7.0 | Coastal marine layer cuts mornings |
| Colorado (Denver) | 39.7° N | 5.5 | 3.5 | 7.0 | High altitude, clear air |
| Connecticut (Hartford) | 41.8° N | 4.0 | 1.9 | 5.8 | Standard New England |
| Delaware (Dover) | 39.2° N | 4.2 | 2.2 | 5.8 | Mid-Atlantic average |
| Florida (Miami) | 25.8° N | 5.4 | 3.7 | 6.4 | Low latitude, but cloudy afternoons |
| Georgia (Atlanta) | 33.8° N | 4.7 | 2.8 | 5.9 | Consistent year-round |
| Hawaii (Honolulu) | 21.3° N | 5.9 | 4.9 | 6.7 | Tropical, near-flat seasonal curve |
| Idaho (Boise) | 43.6° N | 4.9 | 2.5 | 7.0 | Intermountain, strong summer |
| Illinois (Chicago) | 41.9° N | 4.0 | 1.8 | 6.0 | Lake-influenced winters cloudy |
| Indiana (Indianapolis) | 39.8° N | 4.2 | 1.9 | 6.0 | Midwestern average |
| Iowa (Des Moines) | 41.6° N | 4.4 | 2.2 | 6.2 | Continental, clear cold winters |
| Kansas (Wichita) | 37.7° N | 5.0 | 3.0 | 6.6 | Plains, strong sun, wind a factor |
| Kentucky (Louisville) | 38.3° N | 4.4 | 2.5 | 5.9 | Ohio valley average |
| Louisiana (New Orleans) | 30.0° N | 4.8 | 3.0 | 5.9 | Humid Gulf coast |
| Maine (Portland) | 43.7° N | 4.0 | 1.8 | 5.8 | Cold winters limit production |
| Maryland (Baltimore) | 39.3° N | 4.3 | 2.1 | 5.8 | Mid-Atlantic standard |
| Massachusetts (Boston) | 42.4° N | 4.2 | 2.0 | 5.8 | Solid Northeast performance |
| Michigan (Detroit) | 42.3° N | 3.8 | 1.5 | 5.8 | Lake-effect cloudy winters |
| Minnesota (Minneapolis) | 45.0° N | 4.2 | 1.8 | 6.0 | Cold but clear winters |
| Mississippi (Jackson) | 32.3° N | 4.7 | 2.9 | 5.9 | Deep South humid average |
| Missouri (Kansas City) | 39.1° N | 4.6 | 2.5 | 6.3 | Plains transition |
| Montana (Billings) | 45.8° N | 4.6 | 2.2 | 6.8 | Big sky country, clear winters |
| Nebraska (Omaha) | 41.3° N | 4.5 | 2.3 | 6.4 | Plains, dry continental |
| Nevada (Las Vegas) | 36.2° N | 6.4 | 4.4 | 7.8 | Desert, very high year-round |
| New Hampshire (Concord) | 43.2° N | 4.0 | 1.8 | 5.8 | Northern New England |
| New Jersey (Newark) | 40.7° N | 4.2 | 2.0 | 5.8 | Coastal Northeast |
| New Mexico (Albuquerque) | 35.1° N | 6.2 | 4.2 | 7.5 | High desert, very clear air |
| New York (Albany) | 42.7° N | 4.0 | 1.8 | 5.8 | Upstate continental |
| North Carolina (Charlotte) | 35.2° N | 4.6 | 2.7 | 5.9 | Piedmont |
| North Dakota (Bismarck) | 46.8° N | 4.3 | 1.8 | 6.5 | Northern plains, clear winters |
| Ohio (Columbus) | 40.0° N | 4.0 | 1.7 | 5.8 | Lake influence reduces winter |
| Oklahoma (Oklahoma City) | 35.5° N | 5.0 | 3.0 | 6.5 | Southern plains, strong sun |
| Oregon (Portland) | 45.5° N | 3.7 | 1.2 | 6.2 | Cloudy winters, strong summers |
| Pennsylvania (Philadelphia) | 40.0° N | 4.2 | 2.0 | 5.8 | Mid-Atlantic standard |
| Rhode Island (Providence) | 41.8° N | 4.1 | 1.9 | 5.8 | Coastal New England |
| South Carolina (Columbia) | 34.0° N | 4.7 | 2.8 | 5.9 | Sandhills, consistent |
| South Dakota (Sioux Falls) | 43.5° N | 4.5 | 2.0 | 6.5 | Plains, strong summer |
| Tennessee (Nashville) | 36.2° N | 4.4 | 2.5 | 5.8 | Mid-South average |
| Texas (Dallas) | 32.8° N | 5.0 | 3.2 | 6.3 | Very strong; heat derates panels |
| Utah (Salt Lake City) | 40.8° N | 5.3 | 3.0 | 7.0 | High altitude, mountain air |
| Vermont (Burlington) | 44.5° N | 3.9 | 1.6 | 5.8 | Cold continental |
| Virginia (Richmond) | 37.5° N | 4.5 | 2.5 | 5.9 | Mid-Atlantic transition |
| Washington (Seattle) | 47.6° N | 3.5 | 1.0 | 6.0 | Pacific Northwest, long cloudy season |
| West Virginia (Charleston) | 38.4° N | 4.0 | 2.0 | 5.6 | Mountain shadow effect |
| Wisconsin (Milwaukee) | 43.0° N | 4.0 | 1.7 | 5.8 | Lake-effect cloudy |
| Wyoming (Cheyenne) | 41.1° N | 5.2 | 3.0 | 6.8 | High plains, very clear |
Major world cities
Eight reference points outside Europe and the United States. Southern-hemisphere entries show their seasonal pattern reversed: their winter is June to August, their summer is December to February.
| City | Latitude | Annual avg PSH | Winter low | Summer high | Notes |
|---|---|---|---|---|---|
| Sydney, Australia | 33.9° S | 4.6 | 3.0 | 6.0 | Winter is June to August |
| Toronto, Canada | 43.7° N | 3.8 | 1.5 | 5.7 | Lake-effect cloudy winters |
| Tokyo, Japan | 35.7° N | 3.9 | 2.5 | 5.0 | Humid summers cap peak hours |
| Mexico City, Mexico | 19.4° N | 5.5 | 4.2 | 6.5 | High altitude, low latitude |
| São Paulo, Brazil | 23.5° S | 4.5 | 3.5 | 5.5 | Cloudy in austral winter |
| Cape Town, South Africa | 33.9° S | 5.2 | 3.5 | 7.0 | Mediterranean climate, strong summer |
| Dubai, UAE | 25.2° N | 5.8 | 4.0 | 7.0 | Desert, dust derates panels |
| New Delhi, India | 28.6° N | 5.3 | 3.7 | 6.2 | Monsoon reduces summer figure |
How to use these numbers
The first decision is which column to use. For a grid-tied system with net metering, size to the annual average: excess summer production rolls back the meter to cover winter shortfall, so the yearly figure controls your payback. For an off-grid or battery-backed system, size to the winter low: that is the worst-case daily production the battery bank must bridge, and sizing to the annual average is the most common cause of winter blackouts in DIY off-grid setups. The summer high column is mostly diagnostic, useful for checking whether your inverter has enough overhead and whether your battery has enough headroom for excess production.
From PSH the daily kWh estimate is direct: panel kW × PSH × about 0.8 for system efficiency. A 5 kW array in a 4.5 PSH location yields roughly 5 × 4.5 × 0.8 = 18 kWh per day on the annual average. Multiply by 365 to get the yearly figure, around 6,570 kWh in that example. For monthly numbers, scale by the seasonal columns: a system that averages 18 kWh per day annually might produce 30 kWh per day in midsummer and 8 kWh per day in midwinter at the same site.
Tilt and orientation matter. The table values assume south-facing (northern hemisphere) at tilt close to latitude. Flat-mounted panels lose roughly 10% of PSH. East or west orientation costs 15 to 20%; due-north (in the northern hemisphere) loses about half. Steep roofs above 45° favour winter sun at the expense of summer; shallow roofs below 20° favour summer at the expense of winter. The largest single penalty is shade: even a small obstruction shading one cell of a string in conventional string-inverter wiring can cut whole-panel output by 30% or more, which is why microinverters and module-level optimisers exist.
How peak sun hours are measured
PSH is derived from long-term irradiation records, not measured directly. Ground stations, satellites and reanalysis models collect the hourly global horizontal irradiance over many years; PVGIS and NREL then convert that to plane-of-array irradiance for a tilted south-facing module and report the result in kWh/m²/day, which is numerically the same as PSH. The PVGIS database (European Commission Joint Research Centre) covers Europe, Africa and most of Asia using satellite-derived solar resource data combined with meteorological reanalysis. NREL's National Solar Radiation Database covers the United States, Mexico and parts of Central and South America using GOES satellite imagery and surface validation.
Two sources of variation drive the numbers in the tables. Latitude sets the geometric maximum: a low-latitude site receives more direct radiation per square metre at midday because the sun is higher. Climate sets how much of that geometric maximum reaches the panel: a clear desert site captures more than 75% of theoretical clear-sky irradiance over a year, while a coastal cloudy site captures less than 50%. That is why Madrid at 40° outproduces Berlin at 52° by far more than latitude alone would suggest, and why Phoenix at 33° produces more than Atlanta at 34° despite nearly identical latitude.
The values in this reference are typical multi-year annual averages for a representative location in each region or state. Real production at a specific roof can vary ±5% from the table figure based on micro-climate, elevation and orientation, and individual years can swing ±10% from the long-term average. For sizing decisions inside that band, the tables are accurate enough; for engineering-grade design, run your exact coordinates through PVGIS (re.jrc.ec.europa.eu/pvg_tools) or PVWatts (pvwatts.nrel.gov).
Frequently Asked Questions
What is the difference between peak sun hours and daylight hours?
Daylight hours are simply the time between sunrise and sunset. Peak sun hours is the equivalent number of hours per day at the panel's full rated brightness, 1,000 W/m², once weaker morning and evening light and cloudy moments are compressed into the reference value. A summer day in Madrid has about 15 hours of daylight and roughly 7 peak sun hours; the same day in Stockholm has 18 daylight hours but only 5.5 peak sun hours. Panels respond linearly to brightness, so PSH is the figure that predicts production, not daylight count.
Should I use the annual average, winter low or summer high?
Depends on your system type. Grid-tied with net metering: use the annual average, because the grid acts as your battery and only the yearly total matters for payback. Off-grid or battery-backed: use the winter low, because the battery must carry you through the shortest, cloudiest days, and sizing to the annual average reliably produces winter blackouts. Hybrid systems with battery backup plus grid sale: size panels to the annual figure, but check that the battery covers winter daily demand at the winter-low production. The summer high column tells you whether your inverter has enough headroom and whether you should expect curtailment in midsummer.
Why does PSH vary so much between cities at similar latitudes?
Cloud cover and atmospheric clarity, mostly. Latitude sets the geometric ceiling: a site at 40° latitude can capture roughly 6 to 7 PSH on a clear day. How close real conditions come to that ceiling depends on local climate. Madrid at 40° sees roughly 4.9 PSH annual average because central Spain has long dry summers and clear winters. New York at 40° sees only 4.0 because the Northeast is cloudier in winter and humid in summer, both of which scatter direct radiation. Altitude also matters: Denver at 39° gets 5.5 PSH because thinner, drier air lets more radiation reach the panel.
How does panel tilt change peak sun hours?
The table values assume tilt near latitude, the year-round optimum for a fixed mount. Flat (horizontal) loses about 10% versus latitude tilt at mid-latitudes, more at high latitudes. Steeper than latitude (often called "winter tilt", typically latitude plus 10 to 15°) increases winter production at the cost of summer, useful for off-grid sites that are winter-limited. Shallower (latitude minus 10 to 15°) favours summer, useful where summer cooling load dominates. Adjustable mounts gain 5 to 10% annually over fixed-tilt; dual-axis trackers gain 25 to 35% but rarely earn back their cost on residential installs.
How accurate is a PSH-based estimate?
Good enough for sizing, not exact for forecasting. A typical residential PSH-derived estimate is within 5% of long-run actual production for a south-facing, unshaded array at latitude tilt. Year-to-year weather variation adds ±10% noise on top of that, more in cloudy maritime climates and less in arid continental ones. The big losses that overwhelm the PSH estimate are shade (often 20 to 40%), soiling (5 to 10% in dusty climates), and high temperatures (3 to 5% in hot summers because panel power drops about 0.4% per °C above 25°C). For numbers within engineering tolerance, run your exact coordinates through PVGIS or PVWatts and overlay a shade analysis.