C-DRONE GUIDE · 29 JULY 2026
Sunlight and shading studies on a drone 3D model: method, price
Who loses how much sun, at what time, in which season? The question arises in two worlds that ignore each other: real estate, where a building project is blamed for neighbours' loss of sunlight — a classic argument in permit appeals and neighbour disputes —, and solar energy, where a chimney, a tree or the building across the street can cut a photovoltaic roof's output far more than theoretical calculations predict. In both cases, the serious answer requires simulating sun paths over a faithful 3D model of the site — and that is where the drone changes the game: in one hour of flight, photogrammetry captures the neighbourhood as it is, real heights, real roofs, trees included, where models rebuilt from cadastral data ignore everything that sticks up. Method and prices observed in 2026.
Published on 29 July 2026, reviewed on 29 July 2026 — regulations in force as of July 2026.
The problem with theoretical models: they ignore reality
Sunlight studies are classically run on digital models rebuilt from cadastral footprints and standard heights: boxes on a map. Yet real shadows come from what those models do not contain — a gable taller than assumed, a mansard roof, chimney stacks, a twenty-metre cedar in the neighbour's garden. Vegetation, in particular, is the great absentee of theoretical models even though it dominates shading in suburban fabric.
The photogrammetric flight fixes the problem at the root: it produces a digital surface model of the site and its surroundings — buildings, trees, terrain, everything that casts a shadow — with decimetre accuracy, on which sun paths are simulated hour by hour, at solstices, equinoxes or across the whole year. Solar analysis on surface models has long been validated: a study by Andreas Jochem, Bernhard Höfle, Martin Rutzinger and Norbert Pfeifer published in 2009 in Sensors established it for assessing roof solar potential from aerial point clouds (see the study on Google Scholar).
For real estate: permits, appeals and neighbour disputes
For a developer or architect, the sunlight study serves before filing — checking the proposed massing's impact on neighbouring plots, adjusting a profile, documenting the file — and after, when an appeal or a neighbour alleges lost sunlight: the simulation on the real environment shows, hour by hour and season by season, what the project actually changes for each affected façade and garden. It is a far stronger exhibit than a photomontage, and complements the aerial insertion views of the same file.
In neighbour disputes — where abnormal nuisance is judged in part by the sunlight lost —, the same simulation objectively quantifies sun hours before and after, instead of debating impressions. The supporting 3D model is the one we describe in our digital twin by photogrammetry guide; it then serves every other package of the operation.
For photovoltaics: quantifying shading before investing
On a roof or carport, near shading — plant rooms, stacks, parapets, trees, neighbouring buildings — is the first cause of the gap between theoretical and actual output: a shadow on a few modules during peak hours penalises a whole string. Simulation on the drone model computes, panel by panel, shading hours across the year and the associated losses; it guides layout, optimiser choices and, sometimes, the decision not to equip an area.
The study fits naturally into the roof survey before solar panels — same flight, complementary deliverables — and applies equally to ground-mounted projects and car-park canopies, where shading from buildings and street trees is easily underestimated. For an operating plant with disappointing output, the simulation says whether the problem is shading or modules — in which case IEC 62446-3 thermography takes over.
Process and deliverables
The mission has three stages. A photogrammetric flight of the site and its relevant surroundings — typically a 100 to 300 m radius depending on mask heights —, flown RTK to fix the model (our RTK/PPK guide details accuracy levels). The computation: sun paths on agreed dates, hourly shadow maps, annual irradiation maps, before/after comparison for a project. The delivery: dated plates, shadow animations, tables of sunlight hours per façade or losses per roof zone — exhibits readable by a judge, a neighbour or an investor.
In town, the flight follows the rules recalled in our flying in cities guide. The model is reusable: a year later only the vegetation has changed, and a partial update suffices.
Prices observed in 2026
Ranges observed in 2026 (excl. VAT):
- Shading study for a photovoltaic roof (flight + annual simulation, losses per zone): €700 to €1,500.
- Sunlight study for a building project (site + surroundings, before/after, per-façade plates): €1,200 to €2,500.
- Litigation package (dates set by the expert, adversarial plates, metadata): €1,500 to €3,000.
- Update of an existing model: €400 to €800.
The main cost is modelling the surroundings, not the simulation itself — hence the value of pooling the study with the project's photogrammetric survey. Request a quote stating the address, the purpose (permit, litigation, photovoltaics) and the desired simulation dates.