Lay panels out on your actual roof
Several planes, real obstacles, portrait against landscape — and a count you can trust, because a panel is only counted when it genuinely fits.
Lay panels out on your roof
Several planes, real obstacles, and a count you can trust — because nothing is counted that would physically collide.
The module
Roof planes
Obstacles on this plane
Vents, chimneys, skylights, hatches. Position is measured from the plane's top-left corner.
Layout
Panels on this plane
This table is the canvas — everything you can do by clicking, you can do here with a keyboard. Editing a position moves the panel; an illegal position is refused and explained.
Every plane
How this is calculated
Every coordinate is held in metres with the origin at the plane's top-left corner. Rendering scales those to pixels separately, so zooming or switching between feet and metres cannot move a panel.
A panel is placed only when it sits wholly inside the usable area (the plane less your setbacks) and clears every obstacle and every other panel. Auto-fill walks the grid left to right, top to bottom, and skips any position that fails one of those tests — so the same inputs always produce the same layout.
Mixed orientation fills with one orientation first, then tries the rotated module in the strips left over at the right and bottom. It never reports fewer panels than a single orientation would.
Gaps sit between panels, never outside the first and last.
What this drawing is, and what it is not
It is a plan-view arrangement of rectangles that respects the boundaries you gave it. That makes it genuinely useful for sanity-checking a quote, comparing two roof faces, or working out whether a system size is even possible before you spend money on a site visit.
It is not a permit drawing, a structural assessment or an electrical design. It does not know your roof's load capacity, where the rafters run, how the array will be attached, where rapid-shutdown equipment must sit, or what fire-access pathways your local authority requires. Those distances are the ones that most often force a redesign, and no calculator can know them — which is why the setback fields start at zero and warn you rather than filling in a plausible-looking guess.
Slope length or footprint?
If you measured with a tape along the roof, use "along the roof surface". If your dimensions came from a plan, a satellite image or a property map, they are horizontal projections and the real surface is longer — about 12% on a 6:12 pitch, 41% on a 12:12. Choose "horizontal" and enter the pitch, and the height will be corrected before anything is placed. Getting this backwards understates how many panels fit, sometimes by a whole row.
Obstacles are usually worse than they look
A 600 mm vent rarely costs you one panel. It falls in the middle of a row, and because panels are rectangles that must not overlap it, it can cost two or three — and sometimes shifts everything below it. The layout shows the real consequence rather than subtracting an area, and it tells you how many panels each obstacle actually cost.