Best angle for solar panels and how to get it right

Updated: Jul 05, 2024
Created: Dec 25, 2020
10 min

Andrei GorichenskiiAuthor

When we’re talking about efficiency of solar panels, the right positioning is key. An optimum solar panel angle can help you to get even more energy out of your investment! The question of best solar panels’ angle is complicated: it can change with the season and latitude you’re in. Let’s look into it in more detail.

Angle of the solar panel is its vertical tilt

The angle of solar panels corresponds to their vertical tilt towards the equator. Pretty simple: if panels lie flat, their angle is at zero, if they stay perpendicular to ground, the angle is 90 degrees.

In our article on positioning and angle we’ve already discussed the best side for solar panels: in the northern hemisphere panels turned to the south side give you the maximum amount of energy. In the southern hemisphere it’s therefore the north side of the roof. An angle of panels can vary though.

Solar panels installed at a low angle get dirty quicker because the litter doesn’t slide off panels with rain as well

The angle at which solar panels are installed is not always an adjustable thing — sometimes the roof is steep by itself. It’s the easiest to adjust the angle of solar panels installed on flat roofs — they don’t have an initial tilt and panels are easier to access. Ground-mounted solar installations are also easy to adjust. Keep in mind that panels at low angle tend to accumulate dirt and debris faster because all the litter doesn’t slide off panels with rain quite as well.

You can add solar trackers to your system that make the panels follow the sun at all times. Solar panels with trackers can be on average 25-30% more efficient: they squeeze out about 10% more energy in winter and 40% more energy in summer. Obviously, the panels don’t need to be adjusted at different seasons as they adjust themselves. Trackers are expensive though and adding them to a standard residential system is usually not something you can justify economically — not yet at least.

Setting solar panels angle to latitude is fine

If we simplify things, then the angle of your panels can be equal to your latitude. For example, New York’s latitude is 40 degrees, so panels can be installed at 40 degrees angle and their performance will be just fine. You can stop at this point or you can try to optimize your system further.

An angle between 30 and 45 degrees works well across all the US

Latitude number works well for spring and autumn. In summer sun is higher, therefore the angle should be diminished by 15 degrees for best results. In winter the sun is lower and so you have to add 15 degrees to the angle of your panels. For example, in New York your panels’ angle would be at 25 degrees for summer and 55 degrees in winter. However, even this method can be optimized and improved.

Different tilt for each season gives solar panels a little boost

But wait! Is it even worth it to adjust the angle of solar panels though? Let’s look at some data.

Solar panels with a fixed angle capture about 71.1% of the optimum amount of solar energy during the year

Say, solar panels with solar trackers capture 100% of the sunlight they can absorb. the available energy. Solar panels with fixed angle which remains the same for the whole year, receive about 71.1% of the optimum amount of solar energy, according to Charles Landau, senior software engineer and an expert on object-oriented operating systems. When you adjust the angle of your panels two times a year — for summer and winter — it gives you 75.2%. Four-times a year adjustment — for each season — can raise this number only to 75.7%. The reason why this percentage can’t get too high is that solar panels lose some amount of sunlight during the day anyway — there is no “catch-all” angle.

Landau even figured out the date when the switch of angle is optimal. In the northern hemisphere summer switch should occur on March 30. The winter switch is ideal on September 10. In the southern hemisphere, it’s reversed: September 29 works best for summer switch and March 12 is when it’s time to adjust for winter.

There are ways to calculate an optimum angle for solar panels for your state

When solar panels are being tested at Standard Test Conditions, the efficiency number that they receive in the end corresponds to their performance at 77 degrees Fahrenheit, air mass 1.5 spectrum and irradiance of 1000 W/m2. These conditions represent performance of panels when the light hits them at approximately 37 degrees. This means that in the US if the angle of your panels is somewhere between 30-45 degrees, they are probably doing a fine job.

What if you’re determined to find out the optimal tilt for your location? There are a couple of formulas that can give you a more precise number. One of most popular methods among solar designers involves the following procedure:

1. Subtract 2.5 degrees from latitude for spring/fall
2. Multiply your latitude by 0.9
3. Add 29 degrees for the winter angle
4. Subtract 23.5 degrees for summer.

For example, if you are living in New York, then the spring/autumn angle is

40 - 2.5 = 37.5 degrees

In winter it should be:

40 × 0.9 + 29 = 65 degrees

Quite steep, but in theory, it should let panels receive the maximum amount of sunlight during midday hours. Finally, in summer it’s:

40 × 0.9 - 23.5 = 12.5 degrees

Landau, who appeared earlier in this article, claims that for fixed solar panels an angle should be calculated as follows:

• if your latitude is less than 25 degrees, multiply it by 0.87
• if your latitude is more than 25 degrees, but less than 50, then multiply it by 0.76 then add 3.1 degrees.

This method gives you the best angle for solar panels if you don’t plan to adjust them during the year.

If you plan to make corrections for winter and summer, then the formula changes a bit. If your latitude is somewhere between 25 and 50 degrees then you multiply your latitude by 0.93 minus 21 degrees for summer, and you multiply the latitude by 0.875 and add 19.2 in winter.

Let’s continue with New York’s latitude as an example: fixed angle in this situation equals to

40 × 0.76 + 3.1 = 33.5 degrees

This angle should give you about 71% of the maximum amount of sunlight. In a situation where you adjust an angle two times a year, the winter angle is

40 × 0.875 + 19.2 = 54.2 degrees

and the summer’s angle is

40 × 0.93 - 21 = 16.2 degrees

In this configuration your panels catch around 75% of annual sunlight — of course, approximately. Landau himself notes that he describes the most ideal situation, plus points out that the best angle can be different at high altitudes.

Angle of solar panels is not as important as other factors

While these numbers are impressive and all, in practice the changes in performance of solar panels caused by an angle are relatively minor. Factors such as positioning on a roof, weather and especially properties of your model are much more important.

Here is an example: the south side of a roof raises the efficiency of solar panels by 15% compared to those that are installed on an eastern or western side. Trying to get a precise angle each season gives your panels just around 5% more sunlight than just setting the angle to your latitude once and for all. If a homeowner in New York would set his solar panels at 5 degrees for the whole year, he would lose only about 10% of annual production compared to one, whose panels were at 30 degrees — and we’re talking about a 25 degrees difference!