SolarToolsHow This Tool Works
The Solar Panel Tilt & Angle Calculator finds the optimal tilt angle for your solar panels based on your latitude and whether you want to maximize annual, winter, or summer production. Getting the angle right can increase production 5–15% compared to a flat mount, and the math is simple enough to do by hand.
The general rule: for maximum annual production, tilt panels at your latitude angle. For winter production (when sun is lower), add 15°. For summer production (when sun is higher), subtract 15°. This calculator does the math and also tells you whether your existing roof pitch is close enough to optimal for flush-mounting.
If you're in the Northern Hemisphere, panels should face true south (azimuth 180°). In the Southern Hemisphere, face true north (azimuth 0°). Deviations from south/north reduce production — west-facing loses 15–20%, east-facing loses 10–15%.
- Enter your latitude — find it at google maps (right-click your location). North is positive, South is negative.
- Pick your goal — annual (most common), winter (for off-grid systems that need winter sun), or summer (for AC-heavy homes).
- Enter roof pitch — if mounting on a roof. Typical US roof pitch: 18–30°. UK: 30–40°. SA: 15–26°.
- Pick orientation — South for Northern Hemisphere, North for Southern Hemisphere.
The roof note tells you whether flush-mounting on your existing roof is acceptable or if you need tilted racks.
When to Use This Calculator
The latitude rule explained
The sun's angle above the horizon at solar noon equals 90° minus your latitude plus/minus the seasonal declination (±23.5°). To face the sun directly at noon, your panel should be tilted at your latitude angle. This gives maximum annual production because noon is when the sun is strongest.
Why winter and summer differ
In winter, the sun is 23.5° lower than at equinox. Tilting panels steeper (latitude + 15°) catches the low winter sun better. In summer, the sun is 23.5° higher — flatter panels (latitude - 15°) catch it. If you have adjustable ground-mount racks, changing tilt twice a year gains 5–8% production. For roof-mounted systems, the hassle isn't worth it.
Flush-mounting vs tilted racks
Roof-mounted systems are usually flush-mounted (panels parallel to roof) because it looks better and has lower wind loads. If your roof pitch is within 5° of optimal, flush-mounting loses less than 2% production. Within 15°, you lose 3–5%. Beyond 15°, consider tilted racks or a ground-mount.
Azimuth: true south vs magnetic south
True south is not the same as magnetic south (compass south). The difference is magnetic declination, which varies by location — 0–20° in the US. Use the NOAA magnetic declination calculator to find your local value. Facing panels 10° off true south loses about 1% production; 45° off loses 10–15%.
East vs west-facing roofs
If you don't have a south-facing roof, east or west can still work. East-facing produces more in the morning (good for time-of-use plans with high afternoon rates). West-facing produces more in the afternoon (better for peak-rate offset). Both produce 80–85% of south-facing production.
Frequently Asked Questions
For maximum annual production, tilt panels at your latitude angle. For example, at 35° latitude (most of the US South), tilt panels at 35°. For winter production, add 15°. For summer production, subtract 15°.
Only if you have adjustable ground-mount racks. Changing tilt twice a year (steeper in winter, flatter in summer) gains 5–8% production. For roof-mounted systems, the hassle and labor cost isn't worth the small gain.
Yes, but you'll lose 10–15% annual production compared to optimal tilt. Flat panels also collect dust and debris, reducing output further. Minimum recommended tilt is 10–15° to allow rain self-cleaning.
East or west-facing roofs produce 80–85% of south-facing production. West-facing is slightly better for time-of-use rate plans because production peaks during expensive afternoon hours. East-facing is better for morning-heavy usage.
Yes. Steeper tilts (30°+) shed snow better than flat or low-tilt mounts. In snowy climates, a steeper winter tilt (latitude + 15°) helps panels clear snow faster, recovering production sooner after storms.
True south differs from magnetic south (compass south) by your local magnetic declination. Use the NOAA Magnetic Declination Calculator (ngdc.noaa.gov). At solar noon, shadows point due north (Northern Hemisphere) — a simple field method.
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