THE SHORT ANSWER
A useful layout identifies every roof plane, module count, direction and major obstruction. Verify the drawing against safe photos and survey measurements.
Orient the drawing
Find north, street side and each roof plane. Count modules by plane and compare the shapes with ground photos or plans. Do not assume the top of a drawing is north. Label dormers, hips, valleys and attached structures that make one plane distinct from another.
Mark fixed obstructions
Identify vents, skylights, chimneys, mechanical equipment, required access areas and existing rooftop devices. DOE advises considering roof condition and site suitability. [1] An early layout may move after field verification, so ask which objects are surveyed and which are estimated.
Check orientation inputs
NREL PVWatts uses tilt and azimuth as production inputs. [2] Ask which values represent each roof plane and whether the proposal models planes separately when their directions differ. One blended annual number can hide an incorrect orientation entered for part of the array.
Distinguish usable space from chosen space
A blank roof area may be reserved for access, setback, shade, structural or homeowner reasons. Ask for the design rationale without presuming every visible surface should contain panels. Likewise, a crowded concept should not be treated as buildable before code and site review.
Freeze the surveyed revision
After the site survey, request a dated layout showing verified module count and roof planes. Compare it with the proposal’s capacity and production estimate. If modules move or disappear, require the resulting kWdc, energy estimate and scope changes before approving construction.
Before your next conversation
- Find north and label roof planes.
- Count modules on each plane.
- Verify obstructions and orientation inputs.
- Save the post-survey layout revision.
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.
Make the decision specific to your home.
Bring the layout to an Origin Direct design review.
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