SolarMathKit

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Panel orientation

What Is the Best Tilt Angle for Solar Panels?

Find a practical solar panel tilt angle and azimuth for your location. Enter latitude, longitude, and your current roof or mount orientation to compare sampled PVWatts candidates for annual and winter production. This is a location model, not a shade or structural survey.

Compare tilt and azimuth

The tool samples practical angles with PVWatts V8 and compares them with the orientation you enter. It does not inspect roof shape or shade.

PVWatts model assumptionsEditable planning values

Calculating runs a bounded two-pass comparison: practical tilt candidates first, then practical azimuth candidates at the best sampled tilt.

Your sampled orientation estimate

Local calculation

Enter your values, then calculate. Results will show the formula inputs and rounding used.

Formula used

best sampled orientation = arg max PVWatts annual AC kWh across bounded tilt candidates, then bounded azimuth candidates

The first pass compares practical tilt angles around the site's latitude while facing the equator. The second pass compares practical azimuths at the best sampled tilt. A separate winter comparison uses December–February in the Northern Hemisphere or June–August in the Southern Hemisphere.

See the full assumptions and rounding policy.

Maintenance and verification

Maintained by: SolarMathKit Formula version: 1.3.0 Last reviewed:

The calculator calls the shared, tested TypeScript calculation modules documented in the methodology. Automated tests cover published examples, invalid inputs, rounding, and result invariants.

SolarMathKit maintains this implementation. The review is an internal technical check, not an independent engineering certification.

Worked example: compare a low-slope roof

Enter the site coordinates, a current 20° tilt and 180° azimuth, then keep the visible PVWatts assumptions.

  1. Build bounded tilt candidates around the absolute latitude and include the current 20° roof.
  2. Model each tilt with a 1kW reference array and local typical weather.
  3. Use the best sampled annual tilt for a second pass across practical azimuth candidates.
  4. Compare the final sampled annual and winter leaders with the current orientation.
Result: The result reports modeled kWh per installed kW, the sampled gain, and the exact candidates evaluated. It does not claim a continuous mathematical optimum.

Common mistakes to avoid

  • Assuming tilt must always equal latitude.
  • Confusing magnetic compass headings with PVWatts azimuth measured clockwise from true north.
  • Changing a fixed roof design for a tiny modeled energy gain.
  • Ignoring shade, roof geometry, wind, snow, structure, and mounting constraints.

Questions people ask

Is the reported angle the exact optimum?

No. It is the best result among a bounded set of practical candidates. This keeps the comparison understandable and avoids excessive external requests.

What does azimuth mean here?

PVWatts uses degrees clockwise from true north: 0° north, 90° east, 180° south, and 270° west.

Why can the best angle differ from latitude?

Weather distribution, seasonal production, diffuse light, array setup, and the optimization target all affect modeled output.

Does this account for shade?

No. PVWatts typical weather does not inspect nearby trees, buildings, roof obstructions, or a site-specific horizon.

Before you build: Check voltage, current, temperature, protection, cable sizing and installation rules with the equipment manuals and a qualified professional.