Path-Q Solar
How can I estimate whether roof shading changes during different seasons?
Answer
Use a site survey or solar-shading study that examines the roof throughout the year, rather than relying on a single observation or a single aerial image. Compare the sun's position and obstruction shadows at representative times across seasons, especially during the hours the array would produce most of its energy.
Key points
- Observe or model nearby trees, buildings, poles, terrain, and roof features.
- Record the obstruction's height, distance, direction, and whether it changes seasonally.
- Ask for estimated shade losses by roof section, not just a general statement that the site is sunny.
What it depends on
- Roof orientation and tilt
- Location, height, and seasonal behavior of obstructions
- Sun position by month and time of day
- Proposed panel layout and electrical configuration
Risks and trade-offs
- Leaf-off and leaf-on conditions can produce very different results.
- A visual check at one time of year can understate winter or late-day shading.
- Removing or trimming vegetation may change shade but can create cost, maintenance, or property issues.
Information you may need
- Roof orientation and measurements
- Photos or a site survey from multiple directions
- Tree and obstruction heights and seasonal conditions
- Proposed panel locations
Your next step
What to do next
Request a year-round shade analysis for each proposed roof section and ask how its assumptions were measured.
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