How to Calculate the Optimal Solar Panel Tilt for Your Latitude

July 20, 2022
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Recent surveys show that an increasing number of homeowners share an enthusiasm for solar panels. In fact, the Energy Information Administration (EIA) has projected renewables to be the leading source of energy generation. It’s no surprise when about 46 percent of homeowners have given serious thought to adding panels to their homes. 

If you already have solar panels or are giving serious thought to installing a system, 

the first step for those already with solar panel systems or those giving the installation a serious thought is to use a solar ROI calculator. However, without an optimal tilt angle, the ROI can vary greatly because your panels would not be performing at peak efficiency. 

What Is Solar Panel Tilt Angle? 

The tilt angle is the angle made from solar panels to the surface of the ground. It’s always a positive number and mentioned as a degree. 

For example, if the tilt angle is 0°, that would mean the solar panels are flat and parallel to the ground. On the other hand, solar panels with a 90° angle would indicate that they are vertical and perpendicular to the ground. 

Why You Must Optimize Your Solar Panel Tilt

As you drive around, you may notice that solar panels in certain neighborhoods face a different direction and angle than others. Although it’s logical for a person to think that all the panels have to do is face the sun, you must remember that the sun’s position is always changing depending on your time zone and the time of the year. 

So in order for a homeowner to maximize their energy production, they must maximize solar absorption — this is especially important for those with an off-grid solar system

For a homeowner to maximize their solar absorption, the solar panels must have a tilt angle that allows the sun’s rays to be perpendicular to the panels. In other words, the panels must always be at an incline and recalculated to be perpendicular to the sun’s rays. 

However, as briefly mentioned earlier, it’s not a one-and-done installation because the sun’s position is always changing depending on the time, season and time zone. For example, the sun moves from east to west throughout the day and is overhead during summer and positioned toward the southern sky during winter months. That’s why homeowners need to install their systems with an optimal tilt angle that accounts for hourly changes throughout the day and seasonal changes throughout the year. 

Calculating the Optimal Fixed Solar Panel Tilt Angle

There are two types of optimal angles you can calculate. The first and most common type and the most convenient for homeowners and small businesses are fixed solar panel tilt angles. 

Generally speaking, fixed panels use the latitude of the installation location to determine the optimal tilt angle. In other words, the rounded latitude is the optimal tilt angle. 

For example, if you live in New York, which has a latitude of 40.71° N, the optimal tilt angle would be 41°. If you live in Madrid, Spain, which has a latitude of 40.41° N, the optimal tilt angle would be 40°. 

These tilt angles account for seasonal and hourly changes, so your solar panel system will produce power throughout the day. However, it will be the most efficient around noon and during the summer. 

Another general rule is that the optimal tilt angle will be lower and closer to 0° the closer the installation is to the equator, and the higher it will be, up to 90°, the farther away it is. For the U.S., the optimal tilt angle for fixed panels is between 30° and 45°, depending on the state. 

Adjusting the Tilt Angle for Seasonally Adjusted Panels

Suppose you use an off-grid solar system for your vacation home or are simply dissatisfied with your fixed panel’s energy production. In that case, you might prefer a seasonally adjusted panel. This tilt angle is more hands-on but is best for those who want to maximize their energy production during specific seasons. 

For example, the sun is overhead during the summer, so the optimal tilt angle will be to have the panels horizontal and parallel to the ground. On the other hand, during winter, the sun is near the horizon, so the solar panels must be inclined vertically. 

However, during spring and fall, you can calculate the optimal angle similar to how you calculate it for fixed panels. Essentially, the optimal tilt angle during spring and fall is the rounded latitude of the location. 

There are two methods to calculate the optimal tilt angle during summer.

Summer Optimal Angles

The first method is much quicker but has fewer accurate results. You simply take the latitude of the location and subtract 15°. For example, if you live in Boston with a latitude of 42.36°N, you’d round it down to 42° and subtract 15°. In this case, the optimal tilt angle would be 27°. 

The second method is like the first but requires a little more math. Method Two takes the latitude of the location, multiplies it by 0.9, and subtracts 23.5°. The equation, using the same example as the first method, would be 42 x 0.9 – 23.5, which equals 14.3 or 14°. 

As you can see, that still results in a 13° difference between the two methods. For the most accurate results, it’s best to speak with your local solar vendor and see if they have a calculator you can use. 

Winter Optimal Angles

The two methods to determine optimal winter tilt angles are very similar to determining the summer tilt angles. The first method is the exact same, except you add 15 instead of subtracting. So the equation, using the same latitude as above, would be 42 + 15 instead of 42 – 15. 

The second method is also similar. The equation for method two is to take the latitude, multiply it by 0.9 and add 29°. So the equation would be 42 x 0.9 + 29. 

Achieving the Optimal Tilt Angle

The bottom line is that although a solar panel system’s performance is affected by its tilt angle, it’s not a dealbreaker. Yes, you would get the most bang for your buck by adjusting the panels based on altitude and season, but it’s highly likely that you have a fixed system that doesn’t allow for any adjustments throughout the year. 

If that’s the case, there’s no need to worry. As long as the tilt angle of your panels is set to your location’s latitude, you can rest assured that you’re still getting enough power and saving money. 

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