Tilt your solar panels to 37.5° facing south in Marion. That is the most efficient fixed angle for its latitude of 40.55°. The full breakdown, including seasonal and monthly adjustments, is below.
Today, the most efficient tilt for photovoltaic panels in Marion is 36.3°, facing south. At solar noon the sun sits 53.7° above the horizon. Setting your panels to this angle keeps them as close to perpendicular to the sun as possible, which is where they generate the most electricity.
Your photovoltaic panels need to be angled facing south. Marion is in the northern hemisphere, so panels catch the most sun facing south.
If you're mounting the photovoltaic panels at a stationary angle, such as on your roof, the most efficient angle is 37.5°.
If you're planning to change the angle of your photovoltaic panels twice per year, the most efficient angle is 16.7° facing south in summer months and 54.7° facing south in winter months.
When changing the angle of your photovoltaic panels each season, the most efficient angle is 13° facing south in summer months and 60.1° facing south in winter months, and 37.4° facing south in autumn and spring months.
A 400W panel at its best fixed angle in Marion makes about 522 kWh a year, worth $84.75 at 16.23 cents per kWh, the 2025 residential average for Indiana. Per kilowatt of panels that is 1,306 kWh, or $211.88, a year.
A home in Indiana uses about 11,401 kWh of electricity a year, so covering all of it from the roof in Marion takes roughly 22 panels of that size. Fewer panels cover proportionally less of it.
If you adjust your photovoltaic panels every month, the table below gives the most efficient angle for Marion throughout the year. The shallowest angle is 17.1° in June, and the steepest is 63.9° in December.
| Month | Optimal tilt | Sun angle at noon |
|---|---|---|
| January | 60.6° | 29.4° |
| February | 51.7° | 38.3° |
| March | 40.9° | 49.1° |
| April | 28.9° | 61.1° |
| May | 20.4° | 69.6° |
| June | 17.1° | 72.9° |
| July | 20.1° | 69.9° |
| August | 28.7° | 61.3° |
| September | 40.7° | 49.3° |
| October | 52.3° | 37.7° |
| November | 60.9° | 29.1° |
| December | 63.9° | 26.1° |
The sun angle at noon is how high the sun sits above the horizon at midday. Facing your panels south at the tilt shown for each month keeps them as close to perpendicular to the sun as possible, which is where they generate the most electricity.
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It comes out of your latitude. Marion sits at 40.55°, which puts the best fixed angle at 37.5°. Near the equator the midday sun is almost overhead, so panels lie close to flat, around 3°. The further from the equator you are, the lower the sun sits, and the steeper your panels have to stand to face it squarely.
The climb is not one for one. At 30° of latitude the best fixed tilt is about 31°, but at 60° of latitude it is about 46°, not 60°. The optimum flattens off toward the poles because the winter sun is low and much of the light arriving is diffuse rather than direct. Every angle on this page comes from a curve fitted to measured optimal-slope data for 52 cities, so it follows that flattening instead of assuming tilt equals latitude. See how the two compare.
The angle is settled. Here is what is worth checking on the panels themselves:
Generation modeled with PVGIS at this location's own coordinates, © European Union, 2001-2026. Electricity prices from the US Energy Information Administration.