Are you looking for an apartment or a house and would like to know how much natural light actually enters the rooms? The listing photos show a bright living room, but at what time was the photo taken, and in which season? Google Maps and several complementary tools now allow you to answer this question even before visiting the property.
Google Solar API: what the simulation really calculates
Google launched the Google Maps Platform Solar API in 2023-2024. This tool does not just display a map: it models the roofs of buildings in 3D and cross-references these models with historical sunlight data.
Specifically, the Solar API calculates the irradiation received by each section of the roof, taking into account shading created by neighboring buildings, trees, and the terrain. The result provides an estimate of the actual photovoltaic potential of a roof, not a theoretical average based solely on latitude.
For an individual considering installing solar panels, the difference is significant. A south-facing roof that is partially shaded by a neighboring building will produce much less than a roof slightly tilted towards the southwest but completely unobstructed. The Solar API precisely incorporates this type of parameter. Understanding the sunlight simulation on Google Maps allows you to leverage this data before making any investment.
Simulating shadows around a house with 3D tools
The Solar API primarily addresses solar projects. To evaluate the daily light comfort of a home, other tools go further.
Shadowmap: real-time shadow visualization
Shadowmap is a 3D simulator that displays the shadows cast around a building at any date and time of the year. It uses solar vectors and the sun’s trajectory, combined with 3D data of surrounding buildings.
Spotting an apartment on the second floor of a building? Shadowmap allows you to check if the facade will be in shadow starting at 3 PM in winter due to the block of buildings across the street. The shading from neighboring buildings is the most underestimated factor when purchasing real estate.
Sunlight Sim: simulating light room by room
Applications that emerged in 2024-2025 push the logic even further. Sunlight Sim, for example, combines a photo of a room with the house’s position on the map and the sun’s trajectory. The application generates a grid crossing four seasons and four times of day, then assigns a light score to each configuration.
A light score by season and hour replaces the subjective impression left by a twenty-minute visit on a sunny day.
Ground data and satellite data: understanding the limits
Before fully relying on these simulations, some limitations should be clearly stated.
- The 3D models used by the Solar API or Shadowmap are based on surveys that are not continuously updated. A recently constructed building may not yet be included in the data.
- Vegetation is rarely modeled accurately. A large deciduous tree lets light through in winter but blocks some sunlight in summer, which 3D building models do not always capture.
- Reflections and reverberation (glazed facade opposite, light surface on the ground) alter the perceived brightness in a room without appearing in a simulation based solely on shadows.
A field check remains necessary for sensitive projects such as installing solar panels or choosing a home where natural light is a priority.
Solar potential and thermal comfort: two distinct uses
It is tempting to confuse solar potential and thermal comfort, but they are not measured in the same way.
The solar potential, as calculated by the Solar API, measures the energy recoverable by photovoltaic panels. It depends on direct irradiation, roof tilt, and the absence of shade. A roof perfect for solar energy is not necessarily synonymous with a pleasant living space.
The thermal comfort of a house also depends on insulation, wall inertia, ventilation, and the sun-facing glazed area. A south-facing house with large bay windows and poor insulation will overheat in summer. A tool like Shadowmap helps anticipate the duration of direct exposure of facades, but real comfort also depends on the building’s envelope.
To evaluate a solar energy project, the Solar API provides actionable data. To choose a pleasant living space, one must cross-reference sunlight simulation with an analysis of insulation and ventilation.
Practical method for analyzing the sunlight of a property
You have spotted a house or apartment that interests you. Here’s how to leverage these tools in a logical order.
- Open Google Maps in satellite mode and identify the orientation of the building relative to north (always at the top of the screen in standard map mode).
- Use Shadowmap to visualize the shadows cast on the facades and the garden on critical dates: winter solstice (longest shadows) and summer solstice.
- If a solar panel project is being considered, consult the Solar API or a tool like potentielsolaire.com for an estimate of photovoltaic production.
- Validate on-site by visiting the property at two different times of the day, ideally once in the morning and once in the late afternoon.
Cross-referencing digital simulation and field visit eliminates the majority of unpleasant surprises related to the brightness of a property.
These simulation tools are rapidly advancing. The combination of increasingly precise 3D models and historical weather data makes the analysis accessible to any individual, without technical expertise. The point of caution remains the freshness of the data: always check if the immediate environment of the property (new buildings, mature trees) matches what the simulation displays.