Live Demo — Shadow Analysis Calculator
Set your location, date, time and nearby obstacles to see solar angles, obstacle shadow length and obstruction status instantly.
Shadow Analysis Calculator
Free professional shadow analysis calculator for solar lighting projects. Input your site latitude, the analysis date and time, obstacle height, distance and azimuth, plus the panel mounting geometry, to compute the solar position, the obstacle shadow length, and a clear obstruction assessment that protects panel generation from shading loss.
Key Features
Sun Position Parameters
Set local latitude plus a pre-defined calculation date (winter solstice, summer solstice or equinox) and time of day.
Obstacle Parameters
Describe nearby buildings or trees with obstacle height, distance from the panel and azimuth orientation relative to it.
Solar Panel Parameters
Define the panel mounting tilt and azimuth so the obstruction check reflects your actual installation geometry.
Solar Position Calculation
Compute solar declination, elevation and azimuth angles using standard solar-geometry equations.
Shadow Length Calculation
Derive the obstacle shadow length (L = H / tan α) and the resulting shadow range at the panel location.
Obstruction Assessment
Get an instant pass/fail obstruction status and obstruction type, with typical loss guidance for tree, building and self-shading.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | δ = 23.45 × sin(360 × (284 + n) / 365); α = arcsin(sin φ × sin δ + cos φ × cos δ × cos ω); L_shadow = H_obstacle / tan α |
| Latitude | 0° - 60° |
| Calculation Date | Winter solstice / Summer solstice / Equinox |
| Calculation Time | Noon / Morning / Afternoon |
| Obstacle Height | 3 - 328 ft |
| Obstacle Distance | 3 - 328 ft |
| Obstacle / Mounting Azimuth | 0° - 360° / 0° - 180° (0 = due south) |
| Industry Standards | ASHRAE Handbook, EN 17037, IEC 61724-1 |
| Output | Solar elevation (°), solar azimuth (°), shadow length (ft), shadow range (ft), obstruction status + type |
Frequently Asked Questions
How is the solar elevation angle computed?
The calculator first derives the solar declination from the day of the year, then applies the standard formula α = arcsin(sin φ × sin δ + cos φ × cos δ × cos ω), where φ is latitude, δ is declination and ω is the hour angle determined by the selected time of day.
Why analyze at winter solstice noon?
At the winter solstice the sun reaches its lowest noon elevation of the year, so shadows are the longest. If an obstacle does not reach the panel at that worst-case moment, it will normally stay clear for the whole year — the classic design verification point.
How is the obstacle shadow length obtained?
The shadow length is L_shadow = H_obstacle / tan α, i.e. the obstacle height divided by the tangent of the solar elevation angle. The result is compared with the obstacle's distance to the panel to judge whether the shadow actually reaches the array.
What does the obstruction status tell me?
The status reports whether the obstacle shadows the panel at the chosen moment (pass/fail). Typical guidance maps tree shadows to 5-15% generation loss, building shadows to 10-30%, and self-obstruction between rows to 3-8%, helping you decide whether to trim, move or adjust the layout.
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