Solar panel angle calculator
The optimal tilt for your location, and what a system will actually produce — calculated from 30 years of measured irradiance rather than a latitude rule of thumb.
A typical home system is 5–10 kW. Roughly 15 panels for 6 kW.
S (180°) — ideal for the northern hemisphere
Estimated annual production
11,075 kWh
1,846 kWh per kW installed · 923 kWh a month on average
Monthly production
Best month 1,091 kWh · worst month 704 kWh · 1.5× swing
- Optimal tilt
- 29°
- Summer tilt
- 0°
- Winter tilt
- 57°
- Gain vs flat
- +11%
Based on NASA POWER 30-year climate averages for Phoenix and a 78% system performance ratio. Long-term expectation, not a guarantee for any single year. Shading, roof pitch and local rules are not modelled.
Optimal tilt and yield by city
Annual production per kW installed, at each city's optimal angle. This is the number the solar industry calls specific yield, and it is the fairest way to compare locations.
| City | Latitude | Optimal tilt | Gain vs flat | kWh per kW / year |
|---|---|---|---|---|
| PhoenixUnited States | 33.4° | 29° | +11% | 1,846 |
| Los AngelesUnited States | 34.1° | 29° | +11% | 1,777 |
| DubaiUnited Arab Emirates | 25.2° | 20° | +4% | 1,687 |
| DenverUnited States | 39.7° | 34° | +14% | 1,577 |
| MiamiUnited States | 25.8° | 22° | +5% | 1,504 |
| AustinUnited States | 30.3° | 25° | +7% | 1,465 |
| SydneyAustralia | -33.9° | 30° | +10% | 1,462 |
| SingaporeSingapore | 1.4° | 0° | +0% | 1,308 |
| New YorkUnited States | 40.7° | 32° | +12% | 1,247 |
| TokyoJapan | 35.7° | 32° | +12% | 1,239 |
| ChicagoUnited States | 41.9° | 31° | +11% | 1,212 |
| TorontoCanada | 43.7° | 30° | +10% | 1,143 |
| SeattleUnited States | 47.6° | 33° | +12% | 1,088 |
| LondonUnited Kingdom | 51.5° | 36° | +14% | 952 |
| BerlinGermany | 52.5° | 34° | +12% | 901 |
| ReykjavikIceland | 64.1° | 36° | +11% | 716 |
Why the latitude rule of thumb is wrong
The advice you usually see is “set the tilt equal to your latitude”. That follows from geometry alone: it points the panel straight at the sun's average position through the year. But it assumes all sunlight arrives as a direct beam.
In reality a large share is diffuse — scattered by cloud and haze, arriving from the whole sky rather than from the sun's direction. A flatter panel sees more sky and captures more of it. The cloudier the climate, the more the optimum drops below latitude.
You can see this in the table above. Seattle and London sit at similar latitudes to places where the rule works well, yet their optimal tilts land well below their latitude, because so much of their light is diffuse. This calculator uses measured direct and diffuse irradiance for each location and searches every angle from 0° to 90° for the actual maximum.
What the numbers mean
Specific yield (kWh per kW)
Annual production divided by system size. It strips out how big your array is, so you can compare Phoenix with Berlin directly. Anything above 1,600 is excellent; below 1,000 means the economics depend heavily on local electricity prices and incentives.
Gain versus flat
How much tilting beats laying panels horizontally. Near the equator this is almost nothing — in Singapore the optimum is flat. At mid-latitudes it is 10 to 15%, which is usually the difference between a system that pays back and one that does not.
Summer and winter angles
Steeper in winter, flatter in summer, because the sun sits lower in winter. If your constraint is winter output — an off-grid cabin, or a place with winter-peaking demand — optimise for the winter angle and accept a lower annual total.
Frequently asked questions
- What is the best angle for solar panels?
- Roughly your latitude, but almost always a little less. The common rule of thumb ignores cloud cover: where a large share of sunlight arrives as diffuse light scattered by cloud, a flatter panel sees more of the sky and the optimum drops. In Seattle the ideal tilt is around 14° below the latitude; in dry Phoenix the gap is smaller.
- Should panels face exactly south?
- In the northern hemisphere, yes — due south is optimal, and true south, not magnetic south. In the southern hemisphere it is due north. Being 30° off costs only a few percent a year, so an existing roof plane is usually fine. Facing east or west costs roughly 15 to 20%.
- Is it worth adjusting the tilt seasonally?
- Usually not for a fixed rooftop array. Moving between a summer and winter angle twice a year typically gains about 4 to 6% over a good fixed angle — real, but rarely worth the mounting hardware and the roof access. It makes more sense for ground mounts and off-grid systems that are winter-constrained.
- Why does your estimate differ from an installer's quote?
- We model the sun and the climate, not your specific roof. Shading from trees or a chimney, the actual roof pitch, panel degradation over time, inverter clipping and local wiring losses all move the number. Treat this as the ceiling a clean, unshaded array would approach.
- What is a performance ratio?
- The fraction of theoretical output a real system actually delivers, after inverter losses, wiring, soiling and heat. Modern installations land around 0.75 to 0.85; we use 0.78. Hot climates sit lower because panels lose efficiency as they warm.