The efficiency of solar panels is affected by several factors and the tilt angle is one of them. So, finding the right tilt angle for solar panels is critical. However, finding the best angle for solar panels is complicated, since it changes with season and location.
In this blog post, we will discuss four techniques for finding the best angle for solar panels.
What is Meant By the Best Angle for Solar Panels?
If you are still not sure what we are talking about and from what reference the angle is measured. Then don’t worry, I will explain everything to you.
The angle of the solar panel is its vertical tilt towards the equator or simply the angle with the ground. If a solar panel is laid flat then the angle is 0 degrees whereas, if the panel is perpendicular to the ground then the angle is 90 degrees.
The best angle for solar panels is an angle between 0 to 90 degrees depending on the season and location.
Why is Finding the Best Angle for Solar Panels Important?
Solar panels are most efficient when the sun’s rays hit the panel surface perpendicularly. When the angle is oblique the energy is distributed on a larger surface area.
The sun’s rays cover 1 square meter of the area when hit at 90 degrees, and cover over 1.5 square meters when they hit the surface at 45 degrees. So, when the angle decreases, the intensity of energy falls as it is distributed over a greater area.
Energy output is maximum at an angle, which we call the optimum solar panel angle. There is one issue that is the optimum angle keeps changing throughout the year.
Note: Along with tilt angle, solar panel orientation is also important. As a thumb rule, solar panels installed in the northern hemisphere are turned to the south side while in the southern hemisphere, solar panels are oriented to the north side of the roof.
Coming back to the point.
How Often Do I Need to Change the Angle?
This is the most common question that people ask. I can’t adjust the angle every day, what options am I left with? Well, changing the angle daily is good but practically it is not possible. So, to get good energy outputs from the solar panels, the tilt is adjusted a couple of times a year.
Solar panels with a fixed angle give 71.1% energy output given that solar panels with solar trackers give 100% of energy. Whereas, if the angle is adjusted 2 times a year, the output will be 75.2 % while a four times adjustment gives 75.7% efficiency.
The best dates to change the tilt are for Northern Hemisphere for Summer (30th March) and for the Winter angle (10th September), while for Southern Hemisphere the best dates are for summer (29th September) and for winter (12th March).
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Methods of Finding the Best Angle for Solar Panels
Let me tell you some common methods of finding tilt angles for solar panels for different seasons. Usually in the US, solar panels are installed at an angle between 30 to 45 degrees.
Method # 1
If you are planning to install your solar panels with a fixed angle then there are two formulae for calculating the angle.
If the latitude value is less than 25 degrees, the fixed angle is calculated by multiplying latitude by 0.87. And for latitude values more than 25 degrees and less than 50 degrees, the best angle is calculated by multiplying the latitude value by 0.76 and adding 3.1 degrees.
Method # 2
The most simplified method of finding the best angle for solar panels is keeping the tilt angle the same as the latitude value of your area. (You can find your latitude value by making a google search based on your zip code or home address).
For instance, if you are living in New York (latitude of 40 degrees), the best angle for solar panels in New York would be 40 degrees. Likewise, for Miami Florida, it is 25 degrees since its altitude is 25.7617 degrees. It is simple right? But it is not very accurate.
Method # 3
This is another simple method. Here we add 15 to the latitude for the winter angle and subtract 15 from the latitude for the summer angle.
To find the angle for summer in New York, you have to subtract the latitude by 15. For example, subtracting 15 from 40 degrees gives us 25 degrees. The best angle for winter is calculated by adding 15 to the latitude value. For New York, it would be 55 degrees.
This method is not very accurate but it gives decent efficiency.
Method # 4
This method is more accurate and reliable than the first method. In this method, we multiply the latitude value by 0.9 and then add 29 degrees in winter. I.e., if the latitude is 40 degrees, the best angle using this formula would be 65 degrees for winter times.
To find the best angle for summertime, we first multiply latitude by 0.9 and then subtract 23.5 degrees from the answer. I.e., for New York, the best angle using this method would be 12.5 degrees.
While for spring and autumn time, the best angle can be calculated by subtracting 2.5 from latitude. I.e, 40-2.5=37.5 degrees.
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How to Adjust the Angle: Is Solar Tracker Worth the Investment?
There are two ways of changing panel inclination, namely manually or using a solar tracker.
Some solar panels are equipped with solar trackers that make the system follow the sun at all times. The efficiency of such solar panels is on average 25-30 % more than ordinary panels. Now it’s up to you, whether you can afford to install a solar tracker or you want to adjust the angle manually.
While solar trackers may increase the energy output of solar panels, due to the high initial cost, they are not worth the investment, especially for residential uses.
What Other Factors Affect the Efficiency of Solar Panels?
In addition to tilt angle, there are many other factors in play that can affect the efficiency of solar panels. Some of the major factors include:
1. Solar Panel Orientation
Improper orientation will reduce the exposure time to the sun, thus reducing energy output. Hence, solar panels must face the correct direction to receive maximum energy.
As mentioned previously in the Northern hemisphere solar panels should face true south while in the southern hemisphere solar panels are directed towards true north.
It should be noted that true north is different from magnetic north which the compass points at. You need to apply a small correction to find the true north. You may search the web for “Magnetic declination” for your area to correct.
It may be beneficial to have a slight rotation, especially towards the west in the northern hemisphere. The southwest orientation will produce more energy, especially during the evening.
2. Climatic and Environmental Factors
In the northern hemisphere, snow accumulation especially on solar panels with low tilt can completely block the sun’s rays. This significantly reduces the energy output. As per a study, the annual energy loss due to snow accumulation ranges from 1.6% (optimum 53 degrees tilt) to 5.3% at low tilt angles.
Apart from snow, other weather elements include fog, wind, moisture, temperature, mist, and so on.
3. The Roof Where Panels are Installed
The angle, shape, and shading of your roof affect the efficiency of the solar panels. Some roofs don’t offer the flexibility to adjust the tilt angle. In this case, you can install solar panels on the ground.
While for other roof designs, the calculation for solar panel tilt becomes complicated. For proper installation, you need the help of an experienced solar professional.
4. Seasonal Variation
The energy output of solar panels is affected by seasonal variations. During the summertime, the sun will sit higher in the sky while in winter, the sun is lower in the sky. Hence, solar panels receive different energy in each season.
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Conclusion
Now that you know how to calculate the best angle for solar panels in your area. After finding the best angle for each season, you may correct yourself or you may ask a solar professional.
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