THE SHORT ANSWER
Read a preliminary panel layout as a labeled design concept, not a construction approval. Check the building, roof planes, image date, panel assumptions and unresolved obstructions. Google’s Solar API distinguishes underlying imagery dates from processing dates and provides separate roof-segment and panel fields. [1] Ask the designer to explain which information actually supports your proposal.
Confirm the building and the age of the picture
Match the drawing to the correct house, attached garage and any separate structures. Find the street side and north indicator; the top of an image is not automatically north. Compare the outline with current ground-level photographs, especially when a roof, extension or tree has changed. Record a mismatch as an open question rather than accepting a visually attractive overlay as proof of accuracy.
An imagery processing date is not the date the roof was photographed. Ask for the underlying image acquisition date and any known limitations. If that date is approximate or unavailable in the report, preserve that uncertainty. The presence of a Google-derived model does not establish that every feature reflects the property today.
Separate roof direction from panel orientation
Give each proposed roof plane a simple label, such as main rear or garage east. Ask the designer to identify its tilt, direction and panel count. In Google’s reference, roof azimuth uses north as 0 degrees, east as 90 and south as 180. Panel portrait or landscape orientation is relative to the roof segment; it is not a substitute for the roof’s compass direction. [1]
Do not treat a zero azimuth on a nearly flat segment as proof that the modules face north. Ask how the actual mounting arrangement will be represented. If two planes face different directions, a single average input should be explained rather than assumed to describe both accurately.
Reconcile module counts with the proposed equipment
Count modules on each plane and compare the total with the equipment schedule. Record the assumed module model, rated watts and physical dimensions. A model’s default panel size or capacity should not silently become the specification of the equipment you are buying. If the final product differs, ask the designer to check the physical layout and production assumptions again.
Hypothetical example: eight 400-watt modules on one plane and twelve on another total 20 modules, or 8 kW DC of nameplate capacity. This arithmetic does not establish an annual kWh output. The two groups can have different orientation and shade conditions. Ask for the estimate associated with the selected configuration, not a simple assumption that every additional panel contributes identical annual energy.
Distinguish open roof area from approved panel space
Locate skylights, vents, chimneys, valleys and existing equipment, and ask which have been measured versus inferred from imagery. A blank area may reflect shade, access, structural constraints or a homeowner preference. A dense panel overlay can still require revision after professional review. Do not interpret unused image space as an instruction to fill the roof.
Request an explanation of the applicable access and clearance constraints from the qualified designer. This guide does not supply a universal setback dimension or decide which local requirements apply. Ask the project team to resolve conflicts between the preliminary layout, roof condition and permitting requirements before treating the drawing as ready for installation.
Keep the layout tied to the estimate and revision
Save the dated drawing alongside its module schedule and production estimate. If panels move, change model or are removed after the site survey, request the revised count, capacity and energy estimate together. A new picture paired with an old savings report is not a complete revision. Ask which assumptions changed and which remain unverified.
Also distinguish modeled DC energy from the energy expected to reach household or utility metering; ask how the report accounts for conversion and other losses. An annual offset estimate is not a promise of a zero bill or backup power. Use the layout review to decide what evidence is still needed before approving scope, rather than choosing panels solely to reach an attractive savings headline.
Before your next conversation
- Verify the building and underlying image date.
- Label each roof plane and distinguish compass direction from portrait/landscape.
- Match panel count, watts and dimensions to proposed equipment.
- Keep survey changes, production estimates and drawings on the same revision.
Primary sources
- Google Maps Platform: Solar API BuildingInsights reference
Checked October 20, 2026 for imagery dates, roof-segment pitch/azimuth, panel orientation, equipment assumptions and modeled energy fields. These model fields are not an engineering certification or a claim that every field appears in Origin’s interface.
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.
Make the decision specific to your home.
Bring the panel layout and its unanswered questions to a preliminary design review. The final design still depends on site, equipment and permitting checks.
Request an Origin Direct quote →Scope, pricing and availability are confirmed for your property. A request is not a confirmed appointment.
Related guidance
- Prepare safe roof-photo evidence
- Separate system capacity from annual energy
- Reconcile changes after the site survey