Free tool measures a roof from a photo using its tiles as a ruler
Victoria Shinder2 min readGerman company Tegrona has released Tegrona Lite, free software that estimates how many solar modules fit on a roof from a photograph, pv magazine reports. It is aimed at installers and planners who want a first answer during a site visit without CAD tools or measuring the roof.
The interesting part is how it gets geometry out of an ordinary photo. For pictures taken from the ground, where eaves and ridges look distorted and tile rows converge, the software uses the tiles themselves as a reference: because tile rows and columns are parallel on the roof, their lines reveal the vanishing points needed to rectify the image. That also works for trapezoidal and triangular roof faces, where correcting from four corners alone would not be accurate. For scale, the user picks the tile type and the software counts tiles to relate pixels to real dimensions; a single known measurement, such as a roof window, can be used instead. Drone photos and roof plans are accepted too.
Once the roof is outlined and obstacles such as chimneys and skylights are excluded, the tool lays out modules of a chosen size in portrait, landscape or mixed orientation, respecting edge distances, and updates the module count, capacity, area and number of clamps with each change. Layouts export as PDF or PNG over the original photo. All processing happens on the user's device, including in the browser version, so photos are not uploaded; Tegrona points out that this also keeps drone geolocation metadata off its servers. The tool deliberately leaves out yield simulation, shading analysis, string design and structural checks.
What it means
Small tools like this address a real bottleneck in residential solar: the cost of producing a credible first quote. A layout that took a return visit or a CAD session can be sketched in the driveway, which shortens the sales cycle and cuts the number of visits that never turn into a job.
The stated limits matter as much as the features. A module count is not a system design, and the tool says so; shading, wiring and roof structure still need proper engineering before anything is installed. Local processing is a sensible default for a tool that handles photographs of people's homes.