Performance and output
Enter your latitude. See theoretical peak sun hours based on solar geometry alone, split into annual average, summer, and winter figures.
How it works
Step 1
This tool shows the theoretical figure based on solar geometry alone. For a location-specific figure that accounts for local weather, use the peak sun hours calculator instead.
Step 2
Compare these against the seasonal output calculator to see how this same latitude effect plays out in actual system kWh instead of hours.
Based on solar geometry alone, annual average peak sun hours decline gently with latitude, from around 6.6 hours near 25 degrees down to around 5.8 hours near 55 degrees. The bigger effect of latitude shows up in the seasonal swing, not the annual average, which is why this tool breaks the figure into three separate numbers instead of one. A DOE assessment of federal solar systems relies on satellite-based solar resource data with roughly plus-or-minus 10% uncertainty, a reminder that even official irradiance figures carry some margin.
Higher latitudes see a much bigger difference between the sun's summer and winter angle in the sky, which widens the gap between peak and low season peak sun hours. At 55 degrees latitude, summer peak sun hours can run more than double the winter figure, while at 25 degrees the gap is far smaller. NOAA's Solar Calculator can trace this exact seasonal sun-angle swing for any specific latitude and date if you want to see the underlying geometry rather than just the resulting hour figures.
Use it as a starting reference point only. The peak sun hours calculator adds a local climate adjustment on top of this latitude-based figure, which gives a far more accurate number for an actual system sizing calculation. Two locations at the same latitude can see meaningfully different real-world figures once weather is factored in.
Averaging across a full year smooths out the sharp seasonal differences that latitude creates, since a location's high summer months and low winter months roughly balance out over 12 months. This is why the annual figure looks fairly similar across a wide range of latitudes, even though the summer and winter figures diverge sharply. For an off-grid system at higher latitude, that winter low point matters far more than the annual average, since there's no utility connection to smooth over a rough winter stretch, a scenario the northern latitude off-grid winter sizing tool is built around directly.
Add a climate adjustment with the peak sun hours calculator, then feed that adjusted figure into the annual kWh output estimator for a full system-level result. Sun hours also drive how fast a system pays for itself, and that timeline shifts a lot between regions. The payback period by region grouped tool compares payback times across regions for the same system.
Questions
Based on solar geometry alone, annual average peak sun hours decline gently with latitude, from around 6.6 hours near 25 degrees down to around 5.8 hours near 55 degrees. The bigger effect of latitude shows up in the seasonal swing, not the annual average.
Higher latitudes see a much bigger difference between the sun's summer and winter angle in the sky, which widens the gap between peak and low season peak sun hours. At 55 degrees latitude, summer peak sun hours can run more than double the winter figure.
Use it as a starting reference point only. The peak sun hours calculator adds a local climate adjustment on top of this latitude-based figure, which gives a far more accurate number for an actual system sizing calculation.
Averaging across a full year smooths out the sharp seasonal differences that latitude creates, since a location's high summer months and low winter months roughly balance out over 12 months. This is why the annual figure looks fairly similar across a wide range of latitudes.