Apartment Sunlight Checker
Check the seasonal direct-sun window for an apartment, balcony or prospective home before you rent or buy.
Your window in the light.
Sun angle 52.4° · direct sun now · Use the timeline or edit orientation to update
Illustrative scene; drawn objects are decorative · 0.6 m modeled floor reach (8 m room) · flat ground and your own obstacles. Change window dimensions and orientation under “Edit dimensions”.
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 →
7 h 28 m modeled direct sun at this point · 0 user-entered obstacles · two-minute samples · clear sky assumption.
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 00 m |
| 08:00 | 0 h 00 m |
| 09:00 | 0 h 00 m |
| 10:00 | 0 h 00 m |
| 11:00 | 0 h 00 m |
| 12:00 | 0 h 52 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)
- 12:08 WEST–19:36 WEST
Clear-sky geometry, not a weather forecast. Two-minute sampling; time-window edges are approximate. Sun must face the selected window. 0 modeled obstacles; no terrain horizon loaded. Missing geometry is not proof of an unobstructed site.
What reaches your window?
Facing direction changes when direct sunlight can enter. The floor reach below uses your window height and sill.
Illustrative 8 m deep room. The far edge uses sill + window height. Width affects the patch’s width, not this distance; furnishings and overhangs are not included.
| Date | Direct sun | Explore date |
|---|---|---|
| march Equinox2026-03-20 | 7 h 26 m | |
| june Solstice2026-06-21 | 8 h 02 m | |
| september Equinox2026-09-23 | 7 h 24 m | |
| december Solstice2026-12-21 | 6 h 50 m |
Two-minute midpoint samples. 0 modeled obstacles. Counts sunlight facing the window. 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.
Apartment and Balcony Sunlight Checker
Compare the same dates and local times for two prospective homes. Enter the window’s outward-facing bearing and dimensions, then test verified outside screens. Receiver height is a modeling input, not a measurement inferred from the street address.
Use this when: Use this when the primary question is a home, apartment or balcony’s direct-sun exposure, including its facing surface and nearby blockers.
Inputs this tool uses
- The exact facade coordinates, outward-facing true-north bearing and local time zone.
- Window width, height and sill height in metres, plus receiver height above the local ground reference.
- Nearby opaque screens with measured dimensions; save one named scene per candidate.
What this tool calculates
- Direct-sun periods for the chosen facing direction
- Approximate sun reach through a measured window
- Exterior blocking from manually verified nearby structures
- Seasonal sunrise and sunset at the property coordinates
How the estimate is made
Direct sun requires a solar ray above the geometric horizon, in front of the facade and clear of modeled blockers. Floor reach is a simple window projection capped at 8 m. Receiver height changes screen clearance; it does not reconstruct the apartment, balcony slab or neighboring roof.
How to use it
- 01
Confirm the exact facade
Use a plan, compass or map to identify the direction the important window or balcony faces.
- 02
Model the nearest blockers
Enter measured nearby screens and receiver height. Balcony slabs and overhangs need a separate site check.
- 03
Check the worst season
Use the hemisphere’s winter and summer dates. Compare the same local clock time and inspect the window-facing condition.
Worked example
With identical 2.4 m window-top heights and 30° solar altitude, a window facing the sun has about 4.2 m geometric floor reach. Turning its bearing 60° away reduces that to about 2.1 m before considering blockers. This is a constructed comparison, not a claim about a real listing.
How to read the result
Useful comparison
Use the same dates and verified assumptions for each candidate home. Relative differences are often more reliable than a single exact minute.
Confidence
A result becomes stronger when orientation, floor height, window measurements and obstacle heights are all known.
What to do next
Save the two candidates, compare a local winter and summer date, and arrange a viewing near the decisive time. Export the scene to keep the assumptions with your notes.
Limits you should know
- SunCarta does not verify a listing agent’s measurements or building plans.
- Interior brightness depends on glass, finishes, room depth and reflected daylight.
- Never use the result as the only basis for a major property decision; visit at a relevant time when possible.
Questions about this calculator
Can I use a real-estate listing address?
Yes, but the search only centers the map. You still need to pin the exact facade or outdoor point and set its real orientation.
Does a higher floor always receive more sun?
Not always, but additional height can clear a nearby obstruction. Model the receiving point and the blocker elevations carefully.
Methodology version 2.0 · Reviewed September 18, 2026