Solar panel tilt angle calculator
Enter your latitude and get the best tilt angle for your solar panels — year-round, summer and winter — plus an honest estimate of what a non-optimal angle costs you.
Quick answer: for a fixed installation, tilt your panels at roughly 0.9 × your latitude — about 28–36° across most of the US. A few degrees either way changes annual output by only ~1–3%; being far off (e.g. flat at 40° latitude) can cost ~10–15%.
Your setup
Ballpark, not gospel. These are the standard latitude rules installers use for fixed mounts. Local weather patterns, shading and azimuth shift real output ±10% — confirm with your installer before committing hardware.
The formulas this calculator uses
All angles are derived from the absolute value of your latitude L, and every result is clamped to 0–60°:
- Year-round optimum: L × 0.9
- Summer optimum: L − 15°
- Winter optimum: L + 15°
The "your roof vs optimal" figure is a cosine approximation: for each half of the year it takes the cosine of the difference between your tilt and that season's ideal tilt, averages the two halves, and compares the result against the same figure at the year-round optimum. That makes small deviations look small (cosine of a few degrees ≈ 1) and large deviations look costly — which matches how real arrays behave. It ignores seasonal cloud patterns and azimuth, so treat it as approximate.
| Latitude band | Year-round | Summer | Winter |
|---|---|---|---|
| 0–15° | 7° | 0° | 23° |
| 15–30° | 20° | 8° | 38° |
| 30–45° | 34° | 23° | 53° |
| 45–60° | 47° | 38° | 60° |
Reference values at each band's midpoint, computed with the same formulas the calculator uses.
How to use your result
Fixed year-round (most roofs)
Use the year-round angle. Most residential roofs are fixed, and fixed is fine: within ~10° of optimal you lose only ~1–3% annually, so matching a standard roof pitch (18–25°) is usually close enough to be worth the simplicity. Adjustable ground mounts can chase the summer/winter pair above and gain a few percent.
Seasonal adjustment — when it pays
Change tilt twice a year: the summer angle around late March, the winter angle around late September. This buys a few percent of extra annual output over the fixed optimum. It makes sense on pole- or ground-mounted arrays you can reach safely; on a pitched roof the hardware and the trips up a ladder rarely pay back.
Flat roofs
Flat-roof systems use ballasted mounts or tilt frames to reach the year-round angle without penetrations. Many installers set a compromise 5–15° instead: it sacrifices some output but costs less, needs less ballast, and stays low enough to shed rain for self-cleaning. Get a structural engineer's sign-off on wind and snow loads — a tilted panel is a sail.
Questions people actually ask
Straight answers, no fluff. Then run your own numbers above.
What is the best tilt angle for solar panels?
For a fixed year-round setup, roughly 0.9 × your latitude — about 28–36° across most of the US. Steeper than that for winter, flatter for summer. A few degrees either way barely changes annual output.
What tilt should solar panels have in summer vs winter?
A common rule: latitude − 15° for summer, latitude + 15° for winter (both clamped to 0–60°). Seasonal adjustment adds a few percent over a fixed year-round angle — worth it on adjustable ground mounts, rarely worth the hardware on a fixed roof.
How far off can my panel angle be before it matters?
Not far — a few degrees either way typically costs only ~1–3% of annual output (that's what the cosine geometry works out to). What actually hurts is being far off: a flat panel at 40° latitude gives up roughly 15–25% versus the optimal tilt, by the calculator’s estimate.
Can solar panels be installed flat on a flat roof?
They can, but you'll usually want a small tilt anyway: 5–15° frames are standard on flat roofs because they cost little, add noticeable output versus flat, and let rain wash dust off. Ballasted mounts add the tilt without roof penetrations — but get a structural check for wind and snow loads.
Which direction should solar panels face?
Toward the equator: south in the northern hemisphere, north in the southern hemisphere. Direction matters as much as tilt — east/west orientations lose roughly 15–20% versus due south at US latitudes. The calculator's angles assume you can face the panels correctly.
Does tilt matter more at higher latitudes?
Yes. Near the equator the sun is overhead year-round so flat and tilted panels perform almost alike. At 40–50° latitude the sun's path swings much more, and the gap between flat and optimally tilted can reach roughly 15–25% of annual output.
Want the deeper explanation? The best angle for solar panels guide walks through the latitude rule in full. Turning angles into energy? The panel output calculator converts your array into kWh, and the Texas and California state calculators size a full system from your bill. Panel footprints for mounting them are in the solar panel dimensions guide.