Solar Panel Angle Calculator

Solar panels produce maximum power when sunlight hits them at a 90-degree angle (perpendicular to the surface). As the sun moves across the sky and shifts seasonally, the angle between the panel and the sun changes constantly. A fixed panel can only be optimised for one position, so the goal is to find the tilt that captures the most total energy across the period you care about - full year, specific season, or a particular month.

At the equator (0° latitude), the sun passes nearly straight overhead, and the annual rule gives a flat panel: the calculator returns 0° there. Its seasonal figures at the equator are 15° facing north for summer and 15° facing south for winter at the default adjustments, and the result notes that they rest on the rule of thumb alone. At 45°N (Minneapolis, Montreal, Milan), the sun is much lower in the sky, especially in winter. A flat panel there meets the sunlight at a shallow angle. Of the seven NASA POWER sites this page draws on (Miami 25.76°N, Phoenix 33.45°N, Albuquerque 35.08°N, Denver 39.74°N, New York 40.71°N, Seattle 47.61°N, Anchorage 61.22°N), the nearest to 45°N is Seattle, where NASA's model puts a flat panel's yearly energy 11.02% below a panel at its modelled optimal tilt. Use our solar panel output calculator to see how this difference translates into real kWh for your specific panel setup.

The general rule: set your annual tilt angle equal to your latitude. The US Department of Energy Federal Energy Management Program states that the optimal tilt angle for solar exposure equals the local latitude, and the PVWatts documentation calls that setting a common rule of thumb for fixed arrays. The rule balances summer (when the sun is high and panels should be flatter) against winter (when the sun is low and panels should be steeper). NASA POWER's modelled optimal tilt angles, from its 2001-2020 climatology, sit lower: Seattle 31.5°, New York 31.0°, Albuquerque 31.5°. This calculator prints the latitude rule and does not apply NASA's model, so the Seattle preset (47.6°N) returns 47.6° and the New York preset (40.7°N) returns 40.7°, roughly 16° and 10° steeper than those modelled figures.

NASA POWER's model at the five preset cities, each at the latitude of its NASA site:

Across all seven sites in NASA POWER's model, from Miami (25.76°N) to Anchorage (61.22°N), a panel at the latitude tilt collects 96.55% to 99.79% of the yearly energy NASA models at its optimal tilt. For the seasons, here is NASA's mean optimal tilt for June to August and for December to February beside latitude minus 15° and latitude plus 15° (the rule the calculator applies at its default adjustments):

A negative NASA angle means the panel faces north: NASA prints a north-facing optimum for Miami in May, June and July and for Phoenix in June. The ±15° seasonal offsets, the calculator's default adjustments, are a printed rule of thumb. The tilt guide at solarpaneltilt.com says books and articles on solar energy often give the advice of latitude plus 15 degrees in winter and minus 15 degrees in summer. A 2011 conference paper (arXiv 2004.12252) computes seasonal tilts of 16° for summer and 48° for winter at 32.7°N, which is 16.7° below and 15.3° above the latitude. In NASA POWER's monthly series at the seven sites, two positions a year (latitude minus 15° from April to September, latitude plus 15° from October to March) collect 3.37% to 5.16% more energy over the year than a fixed latitude tilt, with each month weighted by its days. Setting the tilt to NASA's modelled optimum every month is the upper bound: 4.44% to 9.15% more. That matters for off-grid systems that struggle in winter. Check your results against your product data or a licensed professional before acting.

These angles are measured from horizontal (0° = flat, 90° = vertical). Each row is the calculator's own result at its default adjustments: summer is latitude minus 15°, winter is latitude plus 15°, and you can change either adjustment above. At 25°N, just south of Miami's NASA site (25.76°N), the calculator adds a note to the summer and winter figures that they rest on the rule of thumb alone. The US Department of Energy Federal Energy Management Program prints the annual rule and a range in a footnote, which begins: "The optimal tilt angle for solar exposure is equal to the local latitude. In the continental United States, a tilt angle between 15°–40° facing south will result in the best production." The seasonal offsets come from the solarpaneltilt.com guide and the arXiv paper cited above, not from DOE. For how close the latitude tilt comes to NASA's modelled optimum, see the first table in the section on why tilt matters.

Fixed-tilt mounts hold the panels at one angle year-round; a panel mounted flush on a roof, parallel to it, takes the roof's pitch as its tilt. Cost: $0 extra beyond the racking itself. Output penalty: in NASA POWER's series at seven US sites, two seasonal positions collect 3.37% to 5.16% more energy over the year than a fixed panel at the latitude tilt; a roof pitch away from the latitude changes that figure. A fixed mount has nothing to adjust; it gives up that seasonal gain.

Seasonally adjustable mounts let you change the tilt 2-4 times per year. Ground-mount systems use these more often than rooftop installations because roof access for seasonal adjustments is impractical and potentially dangerous. Cost: $200-500 extra per array. Prices and rates on this page are our own estimates as of the date shown; they change often. Enter your own figures for a current result. Output gain: two positions (latitude minus 15° from April to September, latitude plus 15° from October to March) collect 3.37% to 5.16% more a year than a fixed latitude tilt in NASA POWER's series at the same seven sites, and retuning to NASA's modelled optimum every month sets the upper bound at 4.44% to 9.15%. Extra winter output matters for off-grid systems. Use the solar panel and battery sizing calculator to spec the full ground-mount system once you decide on adjustable mounts.

Single-axis trackers follow the sun from east to west throughout the day. They boost output 20-35% compared to fixed-tilt and are used on commercial solar farms. Cost: $1,000-3,000 per tracker. For residential use, the math rarely works - the extra cost buys less output than simply adding another panel or two, and the mechanical complexity adds maintenance and failure points. Dual-axis trackers add north-south seasonal tracking and gain another 5-10%, but at $3,000-6,000 per tracker they are strictly commercial-scale equipment.