Guide
Optimizing Solar Panel Placement with a Live Shadow Tracker
A single shadow on a solar panel can cut energy output by 30–50%. This guide shows how to use Shadow Forecaster's live sun arc and shadow tracker to position panels where they receive uninterrupted sunlight — hour by hour, season by season.
Why shadow tracking matters for solar
Solar panels are only as productive as the light they capture. Unlike garden plants, which tolerate dappled shade, photovoltaic cells are wired in series — when one cell is shaded, it acts like a bottleneck and drags down the entire string's output. A sunlight tracker helps you:
- Map exact sun paths across your roof, balcony, or ground mount for the full year.
- Identify obstructions — chimneys, trees, neighbouring buildings — before they cause solar drop-off.
- Plan panel tilt and spacing so rows do not shade each other during low winter sun.
- Time battery charging and appliance use to the hours of guaranteed direct light.
Step 1 — Set your location in the sunlight tracker
Open the Shadow Forecaster home and allow location access. The sun arc redraws for your exact coordinates, giving accurate sunrise, hourly positions, and sunset for today. If you are planning an off-grid cabin or a new roof installation, enter the site coordinates manually in your device settings or move to the location with your phone.
Step 2 — Trace the sun arc across your site
Drag the sun along the arc. The shadow under the tree rotates and stretches in real time, mirroring what a panel would experience. Pause at critical hours and note where shade falls:
- Morning (8–10 am): Check for east-side obstacles and early shading from trees or buildings.
- Solar noon (~12 pm): This is peak yield time — even a small chimney shadow here costs dearly.
- Afternoon (2–4 pm): West-side trees and fences often cast long shadows during peak summer demand.
Step 3 — Identify seasonal shading patterns
The sun rides much lower in winter, so shadows stretch farther and appear from angles that summer planning misses. Re-check the tracker at three key dates:
- Summer solstice (June): Shortest shadows, highest arc — ideal for baseline yield.
- Equinox (March / September): Moderate arc, balanced day length — good for average output estimates.
- Winter solstice (December): Lowest sun, longest shadows — reveals worst-case obstructions.
If a spot is clear at the winter solstice, it is likely safe year-round. If it is shaded in winter but open in summer, treat it as a seasonal panel bank and size your system accordingly.
Step 4 — Avoid inter-row shading
For multi-row ground or rooftop arrays, the front row can cast shadows on the row behind during early morning and late afternoon. Use the tracker to measure the longest shadow your front row will throw at the winter solstice, then add 20% buffer for spacing. A common rule:
- Row spacing ≥ 2.5 × panel height for latitudes 30–50°.
- Row spacing ≥ 3 × panel height for latitudes 50°+.
Tips for off-grid and renewable energy setups
- Photograph your roof or ground mount at 9am, noon, and 3pm on a clear winter day for a permanent reference.
- Orient panels within 30° of true south (northern hemisphere) or true south-facing for best average yield.
- Pair the sunlight tracker with a tilt-adjustable mount — steepen tilt in winter, flatten in summer.
- Re-survey after any nearby construction, tree growth, or antenna installation.
- Use micro-inverters or power optimizers if partial shading is unavoidable — they isolate shaded cells.