When designing rooftop solar PV systems, we often come across this question.

Is the tilt angle important, or is the direction the panels face more crucial?

In a ground-mounted system, you have the luxury of choosing both. But with rooftop installations, especially on tilted roofs, you don’t always get a choice.

What should you optimize for when trying to squeeze every extra unit of generation from your system?

Comparing Tilt Angle vs. Direction Across Multiple Locations

I have analyzed data from eight different sites across six countries, using a 50KW plant with identical modules, inverters, and design. To highlight the impact of weather and insolation, I specifically compared results from India and the US, where conditions vary significantly.

Key Takeaways from the Analysis

• Closer to the equator? Tilt angle matters less. With panels almost flat, direction has minimal impact.
• Between 10° and 30° latitude? Direction becomes more important. This applies to countries like India, UAE, Central Asia, and parts of the USA.
• East-West configuration works best in North Europe and Canada. In other regions, it is less effective.
• Matching tilt angle to latitude is useful mainly in India. In contrast, in the Middle East, Australia, Europe, and the USA, lower angles often generate more power.
• Optimizing for summer generation increases annual output. In colder climates, flatter angles help maximize energy production.

Country-Specific Observations

Australia

• Best setup: 15° tilt facing North.
• Worst setup: East-West configuration.
• Tilt angle is more important than direction.

Germany

• Best setup: 25° tilt facing South.
• Worst setup: High tilt (Winter) facing SE/SW.
• East-West setup provides average results.
• Lower tilt (Summer) gives better annual generation.
• Tilt angle has a bigger impact than direction.

India

• Generation is uniform across configurations.
• Worst setup: East-West configuration.
• Direction impacts generation more than tilt angle.
• Surprisingly, the best setup is tilt at latitude facing South-East.
• Same results in both North and South India.

UAE

• Uniformly high generation across setups.
• Best setup: Latitude tilt facing South.
• Worst setup: East-West configuration.
• Tilt angle impacts generation more than direction.

Uganda

• Located on the equator – best generation across all sites.
• Best setup: Almost flat (1° tilt).
• Minimal variation in direction since panels are nearly flat.
• Increasing tilt angle reduces generation.

USA (California & Boston)

• Best setup: 5°-15° tilt facing South.
• Higher tilt performs better than latitude-based tilt.
• Worst setup: East-West configuration.**
• Tilt angle impacts generation more than direction.

Malaysia

• Best setup: Tilt matching latitude, facing South.
• Worst setup: East-West configuration.
• Minimal variation in direction, as panels are almost flat (3° tilt).
• Increasing tilt angle reduces generation.