How a Real Shading Analysis Actually Works: Tools and Methods

A proper shading analysis maps how shadows actually move across a roof through an entire year, not a single glance during a site visit. The sun's path changes with the seasons, so an obstruction that looks harmless in the afternoon a site surveyor happens to visit can still cast a real shadow across the array at a different time of day or time of year.

Why isn't a quick visual check enough?

A site visit on one particular day and time captures the sun's position at that exact moment, not across the full range of angles the array will actually face over a year of operation. An obstruction that seems clear of the roof in the middle of the day can still cross into shadow territory during early morning or late afternoon hours, when the sun sits at a much lower angle.

This is exactly why a proper analysis needs a method that models the sun's path across the full year, not a method that only confirms what was visible at one specific visit.

What is the Solar Pathfinder, and how does it actually work?

The Solar Pathfinder is an analog device, a concave mirror mounted on a tripod that reflects the surrounding horizon, trees, buildings, anything that could cast a shadow, onto a plastic dome marked with the sun's path for every month of the year. Whatever obstructions appear reflected in the dome directly show which months and times of day will actually be shaded.

It has been a standard tool in the solar industry for decades precisely because it needs no batteries or software, just correct placement and a clear read of the dome. A surveyor traces the visible obstructions against the printed sun-path lines to build an accurate shading picture on the spot.

What does reading a Pathfinder result actually look like?

The printed sun-path lines on the dome are labelled by month, curving from sunrise to sunset. Wherever a reflected obstruction, a tree branch, a neighbouring roofline, crosses one of those lines, that specific month and time of day will be shaded at that exact spot on the roof.

A surveyor reads this directly off the dome at the time of the visit, no calculation or software needed afterward. The device does the work of compressing a full year of sun angles into one physical reading, which is precisely why it remains useful despite newer electronic alternatives.

What about electronic and software-based methods?

Handheld electronic devices exist that capture a fisheye photo of the sky and horizon, then calculate shading loss automatically from that image, a faster process than manually reading a Pathfinder dome. Free software tools, including PVGIS, let a surveyor input a specific location and roof orientation and generate a modelled shading and generation estimate without any on-site device at all.

These tools trade some of the Pathfinder's direct, physical read of the actual site for speed and the ability to model a location before ever visiting it in person, useful for an initial estimate ahead of a full physical survey.

When does a drone-based survey actually earn its cost?

Drone photography captures a roof's surroundings from multiple elevated points quickly, which becomes genuinely valuable on a large or geometrically complex roof where manually tracing sightlines to every potential obstruction by hand would take considerably longer. For a straightforward landed home roof with a small number of clear obstructions, a drone survey is often more capability than the situation actually needs.

The right method scales with roof complexity, not with a fixed idea that more technology always means a better result. A surveyor recommending a drone survey for every job, regardless of roof complexity, is worth asking to justify that recommendation for your specific case.

Does Singapore's sun path change how this analysis should be done?

Singapore's near-equatorial position keeps the sun relatively high overhead across the whole year, without the dramatic low winter sun angle that makes shading a much bigger factor in countries farther from the equator. Shadows here tend to be shorter and change less dramatically month to month than they would elsewhere.

This does not remove the need for a proper year-round analysis, though, since even a shorter shadow from a neighbouring structure can still fall across part of an array during specific hours. It does mean the analysis is confirming a generally more favourable starting position, not searching for a severe seasonal swing the way an equivalent survey farther from the equator would need to.

What should you ask an installer about their shading survey?

Ask specifically what method they use, and whether it accounts for a full year of sun angles rather than conditions on the day of the site visit alone. Ask to see the actual output, a Pathfinder dome photo, a software-generated shading report, or drone imagery, rather than accepting a verbal assurance that shading was checked.

See what shading actually costs in lost output and how to fix it after installation for what happens if a shading issue is missed at this stage. Run the full roof suitability checklist before requesting quotes, and the Sunnify solar estimate to start planning your own installation.