How Many Peak Sun Hours Does Minnesota Get?
Minnesota averages 4.3 to 4.6 peak sun hours a day on a south-facing roof, from about 2.3 in December to 6.4 in July. Here's the data by city and what it means in kWh.
Reviewed by John Ihle, MN Master Electrician (AM005101) · NABCEP-credentialed · iSolar, Saint Paul Park, MN · Last reviewed October 2026
The short answer: Minnesota gets about 4.3 to 4.6 peak sun hours per day on average for a south-facing roof-pitch panel, according to NREL data: about 4.6 in Minneapolis and St. Cloud, 4.4 in Duluth and 4.3 in International Falls. Multiply by roughly 0.75 for real-world losses and you get about 1,260 kWh per kW of panels per year in the Twin Cities.
What a "peak sun hour" actually means
A peak sun hour isn't an hour of sunshine. It's a unit of energy. One peak sun hour equals 1,000 watts of sunlight per square meter for one hour, or 1 kWh per square meter. Solar panels are rated at that same 1,000 W/m² intensity, which is why the unit is so handy.
A clear June day in Minneapolis might have 15 hours of daylight, but the sun is weak in the early morning and evening. Add up all the sunlight that hits a panel over the day and squeeze it into hours of full-strength sun, and you get something like 6 peak sun hours. That's the number that predicts how much electricity a panel makes.
When an installer or a production estimate says "Minnesota gets about 4.6 peak sun hours," they mean the annual average of that daily total on a well-oriented panel.
Minnesota peak sun hours by month and city
The table below uses long-term averages from the National Renewable Energy Laboratory's Solar Radiation Data Manual for Flat-Plate and Concentrating Collectors, built from the National Solar Radiation Data Base. The values are for south-facing panels tilted about 15 degrees less than latitude, roughly 29 to 34 degrees in Minnesota. That's close to a typical 6/12 to 8/12 residential roof pitch.
| Month | Minneapolis | St. Cloud | Rochester | Duluth | International Falls |
|---|---|---|---|---|---|
| January | 3.1 | 3.0 | 2.9 | 2.8 | 2.6 |
| February | 4.1 | 4.1 | 3.9 | 4.0 | 3.9 |
| March | 4.8 | 4.8 | 4.6 | 5.0 | 4.9 |
| April | 5.3 | 5.3 | 5.1 | 5.5 | 5.5 |
| May | 5.8 | 5.8 | 5.7 | 5.7 | 5.6 |
| June | 6.1 | 6.1 | 6.0 | 5.9 | 5.7 |
| July | 6.4 | 6.3 | 6.2 | 6.1 | 5.9 |
| August | 5.8 | 5.8 | 5.7 | 5.5 | 5.4 |
| September | 4.9 | 4.8 | 4.8 | 4.5 | 4.3 |
| October | 3.9 | 3.8 | 3.8 | 3.4 | 3.1 |
| November | 2.6 | 2.6 | 2.6 | 2.4 | 2.1 |
| December | 2.3 | 2.3 | 2.3 | 2.2 | 2.1 |
| Annual average | 4.6 | 4.6 | 4.5 | 4.4 | 4.3 |
Values are kWh per square meter per day (peak sun hours) on a fixed, south-facing panel. NREL lists an uncertainty of about ±9%.
Two things jump out. First, the whole state is surprisingly similar: International Falls averages only about 7% less than Minneapolis. Second, the seasons are not. Minneapolis gets nearly three times as much sun per day in July (6.4) as in December (2.3).
Why Minnesota does better than its reputation
People are often surprised that Minnesota's annual numbers are in the same ballpark as much of the country. A few reasons:
- Long summer days. At 45 degrees north, June daylight runs well over 15 hours. That stacks up big production months from May through August.
- Cold helps. Solar panels are more efficient when they're cool. A bright, cold March day in Minnesota can produce better per hour of sun than a scorching July afternoon.
- Snow reflects light. Fresh snow on the ground bounces sunlight back up, which helps tilted and especially bifacial panels. See our post on bifacial panels in Minnesota snow.
What the table doesn't capture is snow sitting on the panels. The NREL figures measure sunlight available, not what reaches a snow-covered panel. Panels usually shed snow within a day or two of a storm on a sunny day, but December and January production can run below what the table suggests. Our winter production guide covers what to expect.
Converting peak sun hours to kWh per kW
Here's the rule of thumb we use for a quick sanity check:
Daily kWh per kW of panels ≈ peak sun hours × 0.75
The 0.75 accounts for real-world losses: inverter conversion, wiring, panel heat, dust, snow, minor shading and the fact that panels rarely hit their nameplate rating in the field. A well-designed, unshaded system may do a bit better. A shaded one will do worse.
Applied to Minneapolis:
- 4.6 peak sun hours × 365 days × 0.75 ≈ 1,260 kWh per kW per year
- That lines up with what we see on south-facing, unshaded Twin Cities roofs: roughly 1,250 to 1,290 kWh per kW-DC per year, and 1,150 to 1,300 across typical roofs.
- A 10 kW system therefore lands around 12,000 to 12,900 kWh a year, enough to cover most or all of a typical Minnesota home's annual usage.
Winter vs. summer: what 1 kW of panels makes each month
Using the Minneapolis column and the 0.75 rule of thumb, here's what each kilowatt of south-facing panels produces in an average month:
| Month | Peak sun hours | kWh per kW | 10 kW system |
|---|---|---|---|
| January | 3.1 | ~72 | ~720 kWh |
| April | 5.3 | ~119 | ~1,190 kWh |
| July | 6.4 | ~149 | ~1,490 kWh |
| October | 3.9 | ~91 | ~910 kWh |
| December | 2.3 | ~53 | ~530 kWh |
| Full year | 4.6 avg | ~1,260 | ~12,600 kWh |
This seasonal swing is why net metering matters so much in Minnesota. Summer surplus becomes bill credits that carry you through the short days of November through January. Our net metering guide explains how the credits work.
How tilt and direction change your numbers
Peak sun hours depend on how the panel is pointed. NREL's Minneapolis data shows the annual average for south-facing panels at different tilts:
- Flat (0°): about 3.9
- About 30°: about 4.6
- About 45°: about 4.6
- About 60°: about 4.4
- Vertical (90°): about 3.3
Steeper tilts hold up better in winter, flatter ones do better in summer, and most normal roof pitches land near the top of the range. Facing east or west typically costs about 10 to 20% compared with due south. We break that down in our guide to the best roof direction for solar in Minnesota.
Using peak sun hours to size a system
Once you know your annual usage, the peak sun hour math gives you a ballpark system size in about 30 seconds:
- Find your annual usage on your utility account. A typical Minnesota home uses roughly 9,000 to 10,000 kWh a year.
- Divide by your expected production per kW. For a south-facing Twin Cities roof, use about 1,260.
- The result is the system size in kW.
Example: 9,600 kWh ÷ 1,260 ≈ 7.6 kW. With 400-watt panels, that's about 19 panels. If your best roof faces east or west, divide by a number 10 to 20% lower and you'll need a slightly bigger system for the same offset. Our system size estimator runs this for you.
What peak sun hours don't tell you
Peak sun hours describe the sky, not your roof. A few site factors matter just as much:
- Shade. A big oak or a neighbor's spruce can cut production far more than the difference between St. Cloud and Duluth. Winter shade matters most because the sun is low.
- Degradation. Quality panels typically lose about 0.25 to 0.5% of output per year, so year 20 production is a little below year 1.
- Data period. The NREL manual averages 1961 to 1990 weather. PVWatts uses newer satellite-based data that can differ somewhat, and individual years swing, and a smoky or cloudy summer can run several percent below average.
Use peak sun hours to check a proposal
If a quote promises far more than about 1,300 kWh per kW per year on a Minnesota roof, ask how they got there. If it's far below 1,150 on a sunny south roof, ask about shading assumptions. You can also run your address through NREL's free PVWatts calculator, which uses newer satellite-based weather data. For a quick estimate of your own roof, try our roof solar estimator, or request a quote and we'll show the shade analysis behind our production number.
Sources
Frequently asked.
How many peak sun hours does Minneapolis get?
About 4.6 per day on average for a south-facing panel at a typical roof tilt, based on NREL's long-term data. That ranges from about 2.3 in December to about 6.4 in July.
Is Minnesota sunny enough for solar panels?
Yes. Minnesota's annual average of roughly 4.3 to 4.6 peak sun hours supports about 1,150 to 1,300 kWh per kW of panels per year in the Twin Cities. Long summer days and cool temperatures help offset the short winter days.
How do I convert peak sun hours to kWh?
Multiply peak sun hours by your system size in kW, then by about 0.75 to account for real-world losses. For example, 4.6 peak sun hours × 10 kW × 0.75 ≈ 34.5 kWh per day on average.
How many peak sun hours does Minnesota get in winter?
In Minneapolis, NREL data shows about 3.1 in January, 2.6 in November and 2.3 in December for a south-facing panel. Snow sitting on the panels can lower actual production below those figures for a day or two after storms.
Does northern Minnesota get less sun than the Twin Cities?
A little. International Falls averages about 4.3 peak sun hours a day versus about 4.6 in Minneapolis, roughly 7% less. The gap is larger in winter and smaller in spring.
Are peak sun hours the same as hours of daylight?
No. A peak sun hour is 1 kWh of sunlight per square meter. A long summer day might have 15 or more hours of daylight but only about 6 peak sun hours, because early and late sunlight is much weaker.
Have a question we haven't covered?
Talk to a local iSolar expert — free, no pressure. Call (651) 565-1140.