THE SHORT ANSWER
Shade should appear as evidence and an assumption, not a vague adjective. Ask what was observed, how it was modeled and who owns future vegetation decisions.
Map the sources of shade
Use safe ground photos to identify mature trees, neighboring structures, chimneys, dormers and seasonal vegetation. Record approximate direction and time when shade is observed. Do not trespass, prune protected trees or climb the roof for a proposal comparison.
Find the numerical treatment
NREL PVWatts includes system losses but its default loss categories are modeling inputs, not a property shade survey. [1] Ask whether the proposal used a measured shade study, imagery, a separate design tool or a general percentage, and request the dated result.
Separate current and future conditions
A model can describe assumptions about today’s canopy; it cannot promise future tree growth or neighboring construction. DOE notes that shade and site conditions affect solar suitability. [2] Decide which vegetation work, if any, is realistic and authorized before relying on it.
Compare roof-plane consequences
Ask how shade changes module placement and production by plane. If a proposal moves panels to a less productive surface to avoid a tree, compare the modeled tradeoff. A higher module count can still yield a less convincing design when assumptions are hidden.
Preserve a baseline for later questions
Keep shade photos, study output, pruning assumptions and final layout with the proposal. If production changes years later, the service team can compare conditions instead of guessing what the designer observed. The record does not guarantee energy; it makes the estimate auditable.
Before your next conversation
- Photograph visible shade sources safely.
- Request the shade-study method and date.
- Record vegetation assumptions.
- Keep the final shade baseline.
Primary sources
- National Renewable Energy Laboratory: PVWatts Calculator
Primary source reviewed September 10, 2026. Utility rules, equipment availability, project design and contract terms remain specific to the property and proposal.
- U.S. Department of Energy: Homeowner’s Guide to Going Solar
Primary source reviewed September 10, 2026. Utility rules, equipment availability, project design and contract terms remain specific to the property and proposal.
Planning examples and questions are Origin’s editorial guidance, not a property-specific diagnosis, engineering design, tax determination or promise of savings. Manufacturer and utility references do not imply an affiliation with Origin.
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