Path-Q Solar
How does afternoon shade from a neighboring building affect rooftop solar?
Answer
Recurring afternoon shade reduces production during the affected hours, with the impact depending on the shaded area, season, roof orientation, and duration. It can still be worthwhile to use unshaded roof areas, but the loss should be included in a time-based production model.
Key points
- Afternoon shade may matter more or less depending on when the building uses electricity and how exported energy is valued.
- Tall or nearby obstructions can cast longer shadows in winter or when the sun is lower.
- Panel-level or separate-section design may reduce the effect of partial shading but cannot recover sunlight that does not reach the panels.
What it depends on
- Building height, distance, roof orientation, and seasonal sun angles
- Extent and timing of shade across the array
- Electrical design, battery use, and electricity consumption timing
Risks and trade-offs
- A yearly shading percentage can conceal important hourly or seasonal losses.
- Equipment intended to reduce mismatch may add cost and maintenance complexity.
- A future change to the neighboring building or site may alter the production estimate.
Information you may need
- Time-based shade study or measured obstruction profile
- Panel layout showing shaded and unshaded sections
- Hourly electricity use and proposed equipment
Your next step
What to do next
Ask for a shade analysis showing production by month and hour, then compare an unshaded-only design with the full proposed layout.
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SQ00652