Solar Shading Checker
Run a preliminary site solar analysis: modeled direct-sun hours, monthly sample dates and shadow context. Includes a reproducible sunlight analysis example.
Solar times, the sky view and date controls remain available.
Light on this day
Europe/Lisbon · Select any event to move the map to that instant. Times are displayed to the minute; selection keeps the calculated instant.
Sunrise and sunset use an open horizon and atmospheric refraction. Dawn/dusk use the sun’s center at −6°, −12° and −18°. Golden light uses −4° to +6°: a planning convention, not a weather forecast. Calculation notes →
FROM DIRECTION TO DURATION
When does direct sunlight reach here?
2026-09-18 · Lisbon, Portugal · Europe/Lisbon
Each bar shows direct sun within that local clock hour. Clock changes can skip or repeat an hour; repeated-hour totals may exceed 60 minutes.
Read hourly values
| Local hour | Direct sun |
|---|---|
| 00:00 | 0 h 00 m |
| 01:00 | 0 h 00 m |
| 02:00 | 0 h 00 m |
| 03:00 | 0 h 00 m |
| 04:00 | 0 h 00 m |
| 05:00 | 0 h 00 m |
| 06:00 | 0 h 00 m |
| 07:00 | 0 h 36 m |
| 08:00 | 1 h 00 m |
| 09:00 | 1 h 00 m |
| 10:00 | 1 h 00 m |
| 11:00 | 1 h 00 m |
| 12:00 | 1 h 00 m |
| 13:00 | 1 h 00 m |
| 14:00 | 1 h 00 m |
| 15:00 | 1 h 00 m |
| 16:00 | 1 h 00 m |
| 17:00 | 1 h 00 m |
| 18:00 | 1 h 00 m |
| 19:00 | 0 h 36 m |
| 20:00 | 0 h 00 m |
| 21:00 | 0 h 00 m |
| 22:00 | 0 h 00 m |
| 23:00 | 0 h 00 m |
Show direct-sun time windows (1)
- 07:24 WEST–19:36 WEST
Clear-sky geometry, not a weather forecast. Two-minute sampling; time-window edges are approximate. Outdoor receiving point. 0 modeled obstacles; no terrain horizon loaded. Missing geometry is not proof of an unobstructed site.
Where does shade affect your point?
Compare modeled direct-sun hours across the year. This screens obstructions; it does not estimate electricity production.
| Date | Direct sun | Explore date |
|---|---|---|
| march Equinox2026-03-20 | 12 h 00 m | |
| june Solstice2026-06-21 | 14 h 44 m | |
| september Equinox2026-09-23 | 11 h 58 m | |
| december Solstice2026-12-21 | 9 h 18 m |
Two-minute midpoint samples. 0 modeled obstacles. Horizontal outdoor point; no window-facing filter. Clear-sky geometry, not a weather forecast.
A different season. A different light.
Keep your place and jump through the year.
Find your alignment.
Choose what you want to see from Lisbon, Portugal.
1 Choose your target
The pin is where you stand. Mark the landmark or direction you want the sun to line up with.
2 Choose the light
Set precise angles and tolerance
3 Pick your date range
Select a map target first, or open precise angles to enter a direction.
The target sets a compass direction, not the height of a landmark. Windows show when the Sun’s center is within the selected angular tolerance. Terrain, buildings and weather are not included in this alignment search. Near-horizon geometry is not a guarantee of a visible sunrise.
Solar Shading Checker & Site Sunlight Analysis
SunCarta provides an early visual screen for obvious obstruction risks around a proposed solar location. It connects sun direction and altitude to the nearby objects you model, without pretending to replace bankable energy-yield software.
Use this when: Use this when the primary question is an early obstruction screen around a proposed solar location, before detailed energy-yield analysis.
Inputs this tool uses
- An approximate array point with coordinates and receiver height relative to the ground used for nearby obstacles.
- Measured or explicitly estimated screen heights, widths, locations and rotations.
- Representative dates with a local IANA time zone. A map footprint does not establish an obstacle’s height.
What this tool calculates
- Solar altitude and azimuth at the proposed array point
- Screen obstruction checks on representative dates
- Geometric shadow length and bearing
- Sampled clear-ray duration, separate from energy-yield estimates
How the estimate is made
For the array point, each two-minute midpoint contributes its actual elapsed duration when the geometric solar center is above the modeled horizon (0° with the flat default) and no modeled screen blocks the ray. Solar azimuth uses true north. Shadow length is height / tan(altitude), with uncapped numeric output and a 100 km map display clip.
How to use it
- 01
Place the array point
Use the approximate roof or ground location, not only the property centroid.
- 02
Model the horizon
Add measured nearby screens. Use the same ground reference for receiver and obstacle height; missing geometry must remain unknown.
- 03
Check representative seasons
Winter usually creates longer shadows. Compare multiple dates and inspect the hours when production matters.
Worked example
A 10 m obstacle at 30° solar altitude gives a 17.3 m level-ground shadow. If 180 full two-minute intervals remain clear, modeled direct sun is 6 h 00 min. This is not six hours of electrical production; irradiance, panel orientation and equipment losses are separate.
How to read the result
Screening result
A clear result suggests fewer obvious local obstructions; it does not quantify annual kilowatt-hours or electrical losses.
Conservative modeling
When height is uncertain, test a plausible low and high value. A decision that changes across that range needs better data.
What to do next
Run winter, equinox and summer checks, then vary each uncertain obstacle height across a plausible range. Take a changed conclusion as a request for better site measurements and a professional shade or energy-yield assessment before installation.
Limits you should know
- Roof tilt, panel azimuth, row-to-row shading and module electronics are not modeled.
- No weather, irradiance, soiling or energy-yield calculation is included.
- Use professional site assessment and appropriate design software before installation.
Questions about this calculator
Can this replace a solar installer’s shade analysis?
No. It is an early screening and comparison tool. Detailed design requires verified geometry, irradiance data and equipment-specific modeling.
Which date gives the longest shadows?
Near the local winter solstice the midday sun is generally lowest, but morning and afternoon geometry still depends on the obstacle’s direction.
Methodology version 2.0 · Reviewed September 20, 2026