Best Tilt Angle For Solar Panels [Summer + Winter]

Power output for solar panel systems highly depends on solar radiation incidence over the photovoltaic (PV) modules. Installing fixed solar panels might prove profitable in many locations, but ignoring the tilt angle change of the Earth across the year will reduce the performance of the same solar panel system across the seasons. Tilting the modules to a certain degree according to the seasons can improve the solar array’s performance and generate more power.

season of the year and solar radiation
Figure 1: Modeling of the Seasons of the Year – Source: Astronomy Department of the NMSU

This article explains why solar panels are affected by this phenomenon, how you can calculate the right angle to tilt your solar panels at your location, and how to optimize tilting angle for solar panel systems year-round.

Why is the Tilt Angle Important?

The day and night process is caused by the Earth completing a rotation on its axis in approximately 24 hours. I didn’t have to tell you this, but you might not know that this particular axis is tilted to a 23.5 degrees angle. Many theories attempt to explain this inclination, but no matter the cause, this angled rotation is what causes the four seasons throughout the year.

different seasons on earth by earths tilt
Figure 2: Earth Rotation Year-Round around the Sun – Source: NASA

Earth is constantly rotating around the sun, completing a circuit in an average of 365 days or one year. As a consequence of the tilted angle of the Earth, some locations receive different amounts of solar radiation year-round. This fact causes the winters to be cold due to lower solar radiation and summers to be hot as the solar radiation increases.

To make the best out of the available solar radiation, compensating the tilt angle of your panels according to the different positions of the sun will optimize power output for your solar panel system.

Finding your ideal solar panel tilt

Now that you know the theory behind why we tilt our solar panels, we can go ahead and calculate our own.

Don’t be afraid. It is very easy! Using this method, you can figure out the solar panel tilt anywhere in the world.

Finding your Latitude

The ideal angle to place your solar panels is determined by how far you are from the equator. This angular distance of your location from the equator is known as latitude.

Latitude is a vital piece of information for the performance of your solar panel system, so you should learn how to determine the latitude at your location. This can be done by just right-clicking on your location in Google Maps.

latitude on google maps
Figure 3: latitude in google maps

In this example, we can see that the latitude is 38.7°.

Calculating the Tilt Angle

The best way to maximize power output for a PV system is to place solar panels facing directly south (in the northern hemisphere) or north (in the southern hemisphere). This results in PV systems having shallower tilts the further south and higher tilting angles the further north.

  • Summer angle calculation: 0.69*latitude+3.7
  • Winter angle calculation: latitude+10°
  • Year-round angle calculation: (summer° + winter°)/2

If we calculate this for our previous example of 37.7° in Colorado Springs:

  • Summer angle: 0.69*38.7°+3.7= 30°
  • Winter angle: 38.7°+10°=48.7°
  • Year-round angle: (30°+48.7°)/2= 39°

This is particularly useful for ground-mount solar systems that are installed with an adjustable tilt angle racking system. Optimizing for winter is important for off-grid systems. You need the solar array to power your house even under the lowest solar radiation available. Optimizing for summer is mainly for grid-tied cases in which summer electricity consumption and tariffs are much higher during this season.

Conclusion

Understanding how the inclination of the Earth and rotation around the sun affects the angle of incidence of solar radiation grants you powerful knowledge to optimize your solar panel system.

While optimal tilting angle can be obtained from the calculations in the section above, increasing the inclination of your solar panels by 10 degrees during winter or decreasing it by 10 degrees during summer results in your solar panel system generating the highest power output possible for the array. By doing this, you will have more power year-round, higher savings, and quicker ROI.

Frequently Asked Questions (FAQ)

Is it worth tilting solar panels? (Can solar panels lay flat?)

Yes, it is worth tilting solar panels since this provides the highest possible power output of the array. PV modules can lay flat and still produce power, but it is not recommended because of decreased effectiveness and water accumulation during rainfall. Solar panels can be installed in a flat position in countries very close to the Equator and produce a good amount of energy. However, installing solar panels in a flat position in subtropical regions will highly reduce energy output, especially during winter.

Is a west-facing roof OK for solar panels?

Yes, a west-facing roof will still be good enough for placing solar panels but will have up to 20% higher power losses than a south-facing roof. However, in some regions, people prefer to place their panels facing west to match their consumption patterns better and avoid injection to the grid, especially when TOU tariffs (effective during the afternoon) are in place.

How does the angle of a solar panel affect the output?

Solar panel power production is proportional to the amount of solar radiation received by the modules. South facing PV modules at an angle equal to your latitude produces the best performance for the system since modules get the highest radiation. Facing PV modules in other directions decreases the performance by 8% for south-west facing modules up to 20% for west-facing modules.

How much of a difference does tilting solar panels make?

Even if solar panels are directly facing south, tilting them at different angles varies the system’s performance. A difference of 10 degrees can vary power output performance by up to 6% depending on the time of day and location.

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