How to Calculate Solar Panel Tilt Angle
What Is Solar Panel Tilt?
Solar panel tilt is the angle at which your panels are mounted relative to horizontal ground. A panel lying flat has 0° tilt. A panel standing upright has 90° tilt. The goal is to find the tilt angle that captures the most sunlight throughout the year. Because the sun's position in the sky changes with seasons and latitude, the optimal tilt depends on where you live and when you want maximum production.
Why Tilt Angle Matters for Energy Production
Solar panels produce the most electricity when sunlight strikes them at a perpendicular angle — directly face-on. When sunlight hits at an angle, some energy reflects off the glass instead of being absorbed. The difference is significant: a panel at the wrong tilt can lose 10–40% of its potential output depending on your latitude. For example, a flat-mounted panel in New York (40°N) produces about 25% less energy annually than one tilted to the optimal angle. In Phoenix (33°N), the penalty for flat mounting is smaller but still around 15%.
The Simple Year-Round Formula
The quickest way to find your year-round optimal tilt angle is: Latitude × 0.87 + 3.1. For example, if you live at 40°N (New York), your year-round tilt is roughly 40 × 0.87 + 3.1 = 37.9°. In Phoenix at 33°N: 33 × 0.87 + 3.1 = 31.8°. In Port-au-Prince, Haiti at 18.5°N: 18.5 × 0.87 + 3.1 = 19.2°. In London at 51.5°N: 51.5 × 0.87 + 3.1 = 47.9°. This formula performs well across most latitudes and is a solid starting point for fixed-mount systems where you never adjust the angle.
Seasonal Adjustment: Summer vs Winter
For better year-round production, adjust your panels twice a year. In summer, the sun is high overhead — use a shallower tilt. In winter, the sun stays low — use a steeper tilt. The offset depends on your latitude band: Tropical (<25°): Subtract 5° for summer, add 5° for winter. Example: Port-au-Prince (18.5°N) uses 13.5° summer, 23.5° winter. Mid-latitude (25–50°): Subtract 15° for summer, add 15° for winter. Example: Phoenix (33°N) uses 18° summer, 48° winter. High latitude (>50°): Subtract 20° for summer, add 20° for winter. Example: London (51.5°N) uses 31.5° summer, 71.5° winter. Seasonal adjustment captures roughly 90% of the benefit of monthly adjustment with only two trips to your panels.
Monthly Adjustment for Maximum Yield
For the absolute best performance, adjust your tilt each month. The formula is: |latitude - declinationOffset|, where declinationOffset = 23.45 × cos(2π × (month + 10) / 12). This follows the sun's declination throughout the year, creating a smooth sine wave from winter maximum to summer minimum. Monthly adjustments can recover 5–15% more energy compared to a fixed year-round tilt. For example, in New York (40°N), the range goes from 14° in June to 58° in December — a swing of 44°. Most adjustable roof mounts can handle this range easily.
Example: Comparing Three Cities
Let's compare year-round, summer, and winter tilts for three very different locations: New York (40°N): Year-round 37.9°, Summer 25°, Winter 55° — a 30° seasonal swing. This large swing means seasonal adjustment is highly valuable here. Phoenix (33°N): Year-round 31.8°, Summer 18°, Winter 48° — also a 30° swing, but the shallower angles mean more total sunlight captured year-round. Port-au-Prince, Haiti (18.5°N): Year-round 19.2°, Summer 13.5°, Winter 23.5° — only a 10° swing. The tropics enjoy relatively consistent sun angles year-round, so the penalty for a fixed mount is smaller. Use our tilt calculator to see exact numbers for any location.
Common Mistakes When Setting Tilt
Mistake 1: Copying a neighbor's angle. Tilt depends on your exact latitude. A neighbor 50 miles north or south may need a different angle. Mistake 2: Leaving panels flat on a roof. Many roof-mounted panels are installed flush with the roof pitch. While convenient, this rarely matches the optimal tilt unless your roof pitch happens to equal your latitude. Mistake 3: Never adjusting seasonally. A fixed year-round mount is better than nothing, but even one seasonal adjustment per year can boost production by 10–15%. Mistake 4: Guessing by eye. The difference between a 35° and 40° tilt is hard to see but can mean 3–5% lost production. Use a tool like the SolarAlign app to measure precisely.
Frequently Asked Questions
Does tilt matter more at higher latitudes? Yes. At high latitudes (above 45°), the sun arcs low across the sky even in summer, so getting the tilt right has a bigger impact. Can I set my tilt once and forget it? Yes, but you'll leave 10–25% energy on the table compared to seasonal adjustment. Does snow affect optimal tilt? In snowy climates, a steeper tilt (55–65°) helps snow slide off panels. This often aligns well with winter optimal angles anyway. What about flat rooftops? Flat roofs are ideal because you can mount panels at any angle using racking systems. They give you full freedom to set the optimal tilt. Does the [tilt calculator account for roof pitch? The calculator gives the optimal panel angle from horizontal. If your roof is already pitched, subtract the roof pitch from the calculator result to find the mounting bracket angle needed.
Put these numbers to work with SolarAlign
The app uses your phone's sensors to help you align panels to the exact angles discussed in this article. No tools required.Get the app →