Key numbers
- Year-round tilt ≈ your latitude
- Monthly tilt = latitude − solar declination on the 15th
- Seasonal rule: latitude − 15° in summer, + 15° in winter
- Declination swings between +23.45° (June) and −23.45° (December)
On this page
How to use the Solar Panel Angle Calculator
- 1Enter your numbersFill in location, latitude (if other) (°) and month. Every field starts with a typical value you can overwrite.
- 2Check the assumptionsTilt is measured from horizontal. Point panels true south in the northern hemisphere, true north in the southern. The month angle squares the panel to the noon sun on the 15th.
- 3Read the resultsThe calculator shows best tilt for this month, best fixed year-round tilt, summer setting (rule of thumb), winter setting (rule of thumb), noon sun height this month and face the panels, and updates as you type.
- 4Use the resultCompare it with your bill, a quote or a product spec sheet before you buy or install anything.
Results update as you type. Back to the calculator ↑
This solar panel angle calculator gives the tilt that points your panels most directly at the sun for any month, plus a fixed year-round angle and simple summer and winter settings. Pick a city or enter your latitude, choose a month, and read the result.
How the solar panel tilt is calculated
The best tilt for a month is the angle that makes the panel square to the noon sun on the 15th of that month.
- Monthly tilt = |latitude| − solar declination (declination signed toward your hemisphere)
- Solar declination δ = 23.45 × sin(360/365 × (284 + day of year)), the Cooper (1969) equation
- Year-round tilt = |latitude|
- Summer tilt = |latitude| − 15°; winter tilt = |latitude| + 15°
- Noon sun height = 90° − |latitude − declination|
Solar declination is the latitude where the sun is directly overhead at noon. It moves between +23.45° at the June solstice and −23.45° at the December solstice (PVEducation).
Worked example with the default inputs
The default is Denver, Colorado, at latitude 39.7°, in June.
- June 15 is day 166 of the year.
- Declination = 23.45 × sin(360/365 × 450) = about +23.3°.
- Monthly tilt = 39.7 − 23.3 = 16°.
- Noon sun height = 90 − 16.4 = 74° above the horizon.
- Year-round tilt = 40°, summer setting 25°, winter setting 55°.
- Face the panels true south (180°).
Best angle for solar panels by city
All values are tilt from horizontal for the 15th of the month, computed with the calculator’s formula.
| City (latitude) | March | June | December | Year-round |
|---|---|---|---|---|
| Miami, FL (25.8°) | 29° | 2° | 49° | 26° |
| Houston, TX (29.8°) | 33° | 6° | 53° | 30° |
| Phoenix, AZ (33.4°) | 36° | 10° | 57° | 33° |
| Denver, CO (39.7°) | 43° | 16° | 63° | 40° |
| New York, NY (40.7°) | 44° | 17° | 64° | 41° |
| Seattle, WA (47.6°) | 50° | 24° | 71° | 48° |
| Anchorage, AK (61.2°) | 64° | 38° | 85° | 61° |
Notice the June angles are much flatter than the December ones. The winter sun sits low, so panels must stand more upright to face it.
What affects the best angle
Fixed or adjustable mount. A rooftop array is almost always fixed, so the year-round angle (about your latitude) is the target. A ground mount or RV panel can follow the monthly angle.
When you need the energy. An off-grid cabin used mostly in winter should favor the steeper winter angle, because that is when sunlight is scarce. See the off-grid solar system guide for seasonal sizing.
Snow. Steeper panels shed snow faster, another reason to lean toward the winter setting in snowy climates.
Roof pitch. A 6/12 roof pitch is about 27° and a 12/12 pitch is 45°. If your roof is within about 10–15° of the ideal, flush mounting is usually the better value.
Azimuth. Tilt is only half of the aim. Use the solar position calculator to see where the sun is through the day and check shading from trees or buildings.
Fixed, adjustable or tracking mounts
A fixed mount set at your latitude is the simplest and most common choice, and it is what almost every home rooftop uses. An adjustable mount lets you switch between the summer and winter angles, which suits ground arrays, RVs and boats where you can reach the panels safely. A single-axis or dual-axis tracker follows the sun automatically through the day; it gathers more energy per panel but adds moving parts, cost and maintenance. For most homes, adding one more fixed panel is cheaper than adding a tracker, so the calculator focuses on fixed and seasonal settings.
History of the declination equation
The declination formula in this calculator comes from an unlikely place: a paper on solar stills. In 1969 P. I. Cooper published “The absorption of radiation in solar stills” in the journal Solar Energy, and its compact sine approximation, δ = 23.45° × sin(360/365 × (284 + n)), became the standard shortcut in solar engineering textbooks (Cooper, 1969). The 23.45° amplitude is the tilt of Earth’s axis, and the 284-day offset places zero declination near the March equinox.
The equation is accurate to within about a degree, which is ample for choosing a panel tilt. Astronomers and tracker makers use longer series, such as those behind NOAA’s solar calculator, when sub-degree accuracy matters.
| Year | Milestone | Source |
|---|---|---|
| 1969 | Cooper publishes the sine approximation for solar declination | Solar Energy 12:333 |
Tips for setting the tilt
- Measure the roof or rack angle with a phone inclinometer app, laid flat on the panel frame.
- Correct your compass for magnetic declination before setting azimuth.
- If you adjust only twice a year, switch to the summer angle around the March equinox and to the winter angle around the September equinox.
- Once the angle is set, size the array with the solar panel calculator.
References
- Cooper, P. I. (1969). “The absorption of radiation in solar stills.” Solar Energy, 12(3), 333–346. doi:10.1016/0038-092X(69)90047-4
- Honsberg, C., & Bowden, S. “Declination Angle.” PVEducation. pveducation.org
Tilt is one small decision within the bigger choice of how to use renewable energy at home. For the physics of why angle matters, read how solar panels work.
FAQ
Frequently asked questions
What is the best angle for solar panels?
For a fixed panel that never moves, the best year-round tilt is close to your latitude, for example about 40° in Denver or 34° in Los Angeles. If you can adjust the panels, use about latitude minus 15° in summer and latitude plus 15° in winter, or the exact monthly angle from the calculator.
Is tilt measured from horizontal or vertical?
This calculator measures tilt from horizontal. 0° means the panel lies flat and 90° means it stands vertical like a wall. Most roof pitch apps and inclinometers also read from horizontal, so you can compare directly.
Which direction should solar panels face?
In the northern hemisphere, face fixed panels true south, which is an azimuth of 180°. In the southern hemisphere, face them true north. True south differs from magnetic south by the local magnetic declination, so correct your compass reading.
How much do I lose if my roof angle is not ideal?
Usually less than people expect, because output falls with the cosine of the angle error, and a 10° error loses under 2% of direct sunlight. Most installers mount panels flush to the existing roof pitch rather than adding tilt racks.
Should I change the angle of my panels each season?
Adjusting twice a year, in spring and fall, captures most of the gain from seasonal tilting. Monthly changes add a little more. It is practical for ground mounts and RVs, but rarely worth it on a roof.
Why is the summer angle so flat?
In summer the noon sun is high in the sky, so a flatter panel faces it more squarely. In Denver the June noon sun reaches about 74° above the horizon, so a 16° tilt points the panel straight at it.
Does the calculator work in the UK, Canada, Australia or New Zealand?
Yes. The angle depends only on latitude, so it works anywhere. Pick London, Toronto or Sydney from the city list, or choose Other and type your latitude, which you can read from any map for your address or ZIP code. Enter southern-hemisphere latitudes as negative numbers and face those panels true north.
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Last updated October 25, 2026. Part of our renewable energy toolkit. Found an error? Tell us.