Solar Panel Tilt Angle Calculator
5 Solar Panel Tilt Calculation Methods
Here are 5 different ways to calculate the optimal solar tilt angle for your location:
- Our Solar Panel Tilt Angle Calculator
- Simple Rules of Thumb
- An Excel or Google Sheets Spreadsheet
- The PVWatts Calculator
- A Stanford Research Team's Tilt Angle Formula
Let's run through each way, step-by-step.
1. Our Solar Panel Tilt Angle Calculator
Scroll up to our solar panel angle calculator at the top of this page.
In the box, enter a location such as your address, city, or zip code. I live in Atlanta, GA, so I typed "Atlanta" into the box.
Then select your location from the dropdown results. I selected the top result: "Atlanta, GA, USA".
The calculator will calculate the optimal year-round solar tilt angle (from horizontal) for your location. Mine is 28.6°.
Scroll down and you'll see it also calculates your best tilt angles by season and month. Here are mine:
Alternatively, you can just click "Use Your Current Location".
Then click "Allow" when the site asks to use your location.
The calculator will then use your current location to calculate your optimal solar tilt angle.
2. Simple Rules of Thumb
Don't wanna mess with any solar tilt calculations?
Here are 2 simple rules of thumb for finding your tilt angle:
Rule of Thumb: Set your solar panel tilt angle equal to your latitude.
Seasonal Adjustments: Subtract 15° in the summer. Add 15° in the winter.
And if you wanted to adjust your solar panels every month, you could just adjust them by 5 degrees each month -- bottoming out in June and maxing out in December in accordance with the summer and winter solstices.
To find my latitude, I went to Google Maps. Then I clicked on the map near my location. (For this example I just clicked in the center of Atlanta.)
Once I did, I saw my location's latitude and longitude coordinates at the bottom of the map. The first number is my latitude.
According to Google Maps, my latitude is 33.7°.
Thus, using these rules of thumb:
My optimal year-round tilt angle: 33.7°
My optimal tilt angles by season:
- Spring: 33.7°
- Summer: 18.7°
- Fall: 33.7°
- Winter: 48.7°
3. An Excel or Google Sheets Spreadsheet
Here's a simple spreadsheet for calculating the ideal angle for your solar panels:
How to save your own copy of the spreadsheet
1. Click "View the Spreadsheet" above.
2. If using Excel, go to File > Download > Microsoft Excel (.xlsx) to download your own copy. Open it in Excel.
3. If using Google Sheets, go to File > Make a copy. (You must be logged in to Google for this option to be available.)
4. Then click OK to save your own copy to your Google Drive.
How to use the spreadsheet
1. Enter your latitude.
2. Locate your optimal year-round tilt angle. The spreadsheet includes a formula that will automatically calculate the angle based on your latitude.
3. Scroll down to locate your optimal tilt angles by season and by month. These are seasonal and monthly adjustments based on the simple rules of thumb mentioned above.
Note: You do not need to send me a request for editing permission to use this spreadsheet. Just download it or make a copy following the instructions above.
4. The PVWatts Calculator
The PVWatts Calculator is a solar energy calculator made by the National Renewable Energy Laboratory (NREL).
It's the gold standard for estimating how much solar energy your system will produce.
How to use PVWatts to find your optimal solar tilt angle
1. Enter your address then click "Go". For this example I've entered the address of Atlanta City Hall.
2. On the Solar Resource Data page, scroll down to the map to confirm that the calculator found the right location. If it did, click "Go to system info". (If it didn't, click "Change Location" and try again.)
3. On the System Info page, experiment with different values in the "Tilt (deg)" field until you find the tilt angle that generates the most electricity. Start by typing in a number, then click "Go to PVWatts results". I entered "29" as my first tilt value.
Tip: Use our solar panel tilt angle calculator at the top of the page to get an angle to use as your starting point in PVWatts. I did this and got 28.6° which I rounded up to 29°.
4. Note the estimated system output. At 29° tilt, this solar power system at my location would generate an estimated 5,809 kWh per year.
5. Go back to the System Info page and edit the tilt number up and down in increments of 1 until you find the tilt angle that generates the most solar energy at your location. After trying many different numbers, I found that 31° and 32° are my year-round optimal tilt angles -- both would generate an estimated 5,814 kWh per year.
Note: There's no way for the PVWatts Calculator to just tell you the optimal tilt angle. You'll just have to use trial and error. Also, the calculator does not give you the option to input seasonal or monthly tilt angle adjustments.
H/T to The Solar Nerd whose article taught me this solar tilt calculation method.
5. A Stanford Research Team's Tilt Angle Formula
Our solar panel tilt calculator is based on a Stanford research paper.
The researchers behind it analyzed optimal solar tilt angles for all countries worldwide. Then, they produced two formulas to calculate the optimal tilt angle for any given location.
What are these magical formulas, you ask?
If you live in the northern hemisphere (latitude > 0):
Optimal tilt angle (northern hemisphere) = 1.3793 + Φ(1.2011 + Φ(-0.014404 + Φ0.000080509))
(Φ = latitude)
If you live in the southern hemisphere (latitude < 0):
Optimal tilt angle (southern hemisphere) = -0.41657 + Φ(1.4216 + Φ(0.024051 + Φ0.00021828))
(Φ = latitude)
There you have it:
A simple, research-backed way of calculating the optimal tilt angle of your solar panels.
Note: These are the formulas under the hood of our solar panel angle calculator at the top of the page.
Like I explained above, I used Google Maps to find my latitude.
Doing so, I learned that my latitude is 33.7°.
Because my latitude is greater than 0, I can use the first formula listed above to calculate my best solar panel tilt angle:
My optimal year-round tilt angle = 1.3793 + Φ(1.2011 + Φ(-0.014404 + Φ0.000080509))
Φ = 33.7°
My optimal year-round tilt angle = 1.3793 + (33.7°)(1.2011 + (33.7°)(-0.014404 + (33.7°)0.000080509))
After busting out my calculator (and doing a quick refresher on the order of operations), I get the following:
My optimal year-round tilt angle: 28.6°
(Because our calculator uses these formulas, we got the same answer as our calculator.)
If I want to adjust my solar panels seasonally or monthly, I can add and subtract to this angle based on the rules of thumb described above.