Solar & Daylight Data
Daylight & Orientation: Perth, Australia
Monthly and seasonal sunlight on each wall orientation and the roof in Perth, Australia, with cloud cover.
On this page
Last updated September 25, 2026 · Location: GeoNames point -31.9522, 115.8614 ([GeoNames AU dump](https://download.geonames.org/export/dump/AU.zip), CC BY 4.0, ID 2063523); time zone Australia/Perth from the same GeoNames record. Sun positions, sunrise and sunset calculated by Harth with [NOAA's solar calculator equations](https://gml.noaa.gov/grad/solcalc/calcdetails.html), including standard atmospheric refraction, for a sea-level horizon. Sunlight, cloud and air temperature: [NASA POWER climatology](https://power.larc.nasa.gov/docs/services/api/temporal/climatology/) monthly means for 2001–2020 at this point (API v2.10.0, retrieved 2026-09-25).
Direct answer
A north-facing wall in Perth receives 1,262 kWh/m² of sunlight a year and 352 kWh/m² in June–August, the most winter sun of any wall. In December–February the east and west walls take the most, 395 kWh/m² each, while a south wall gets 550 kWh/m² a year. A flat roof receives 2,021 kWh/m² a year. Cloud cover averages 47%, lowest in January and highest in July. East and west walls each receive 1,157 kWh/m² a year, 34% of it in December–February. In January, the clearest month, a flat roof receives 8.2 kWh/m² a day and the clearness index reaches 0.69. North-east and north-west walls receive 1,303 and 1,302 kWh/m² a year; south-east and south-west walls 799 and 798.
Content and cited inputs reviewed by Harth team · Published 2026-08-26 · Updated 2026-09-25.
How much sunlight does each Perth facade get, month by month?
Total solar energy reaching a square metre of wall or flat roof in each month, in kWh/m², from NASA POWER all-sky averages for 2001–2020.
| Month | Roof | North | East | South | West | Cloud cover |
|---|---|---|---|---|---|---|
| January | 254 | 76 | 139 | 73 | 138 | 33% |
| February | 205 | 89 | 115 | 51 | 115 | 37% |
| March | 188 | 123 | 109 | 43 | 109 | 40% |
| April | 134 | 126 | 80 | 34 | 80 | 51% |
| May | 104 | 129 | 64 | 27 | 64 | 54% |
| June | 82 | 115 | 52 | 23 | 52 | 59% |
| July | 90 | 117 | 56 | 25 | 56 | 60% |
| August | 116 | 120 | 70 | 32 | 70 | 58% |
| September | 151 | 113 | 88 | 40 | 88 | 53% |
| October | 203 | 102 | 114 | 51 | 114 | 45% |
| November | 233 | 80 | 128 | 67 | 128 | 40% |
| December | 261 | 73 | 141 | 82 | 141 | 36% |
Yearly and seasonal sunlight by orientation in Perth
| Surface | Year (kWh/m²) | June–August | December–February | Share of year in December–February |
|---|---|---|---|---|
| Roof | 2,021 | 289 | 720 | 36% |
| North | 1,262 | 352 | 237 | 19% |
| North-east | 1,303 | 285 | 341 | 26% |
| East | 1,157 | 178 | 395 | 34% |
| South-east | 799 | 93 | 319 | 40% |
| South | 550 | 80 | 206 | 37% |
| South-west | 798 | 93 | 319 | 40% |
| West | 1,156 | 178 | 394 | 34% |
| North-west | 1,302 | 285 | 341 | 26% |
How clear the sky is over Perth
Cloud cover averages 47% over the year, from 33% in January to 60% in July. The clearness index — the share of sunlight above the atmosphere that reaches the ground — peaks at 0.69 in January. A flat roof receives 2,021 kWh/m² a year, 8.2 kWh/m² a day in January.
Choosing orientations in Perth
For winter sun, the north facade is the one to glaze: it collects 352 kWh/m² over June–August, against 80 for the south facade. In December–February the east and west facades take the most sun, 395 kWh/m² each, so large glazing there needs external shading or low-g glass. The south facade gets the steadiest, mostly diffuse light — 550 kWh/m² a year — which suits studios and deep-plan rooms that need daylight without glare.
How these figures were calculated
NASA POWER gives mean daily global and diffuse sunlight on a horizontal surface for each month. Harth split each day into 10-minute steps with the Collares-Pereira & Rabl and Liu & Jordan profiles, projected each step onto vertical walls with an isotropic sky and ground reflectance of 0.2, and multiplied by the days in the month. East and west come out equal because the averages are symmetric about solar noon; on a real site, afternoon cloud, neighbouring buildings and trees change the split.
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Sources and method
Location: GeoNames point -31.9522, 115.8614 (GeoNames AU dump, CC BY 4.0, ID 2063523); time zone Australia/Perth from the same GeoNames record. Sun positions, sunrise and sunset calculated by Harth with NOAA's solar calculator equations, including standard atmospheric refraction, for a sea-level horizon. Sunlight, cloud and air temperature: NASA POWER climatology monthly means for 2001–2020 at this point (API v2.10.0, retrieved 2026-09-25).
Source links
Frequently asked questions
Which way should a house face in Perth for winter sun?
Face the main living spaces north. In Perth a north-facing wall receives 352 kWh/m² of sunlight over June–August, compared with 178 for east or west and 80 for south.
How much sun does a west-facing wall get in Perth in summer?
About 394 kWh/m² over December–February, 34% of its yearly 1,156 kWh/m², arriving as low afternoon sun that overhangs do not stop.
How cloudy is Perth?
NASA POWER satellite records for 2001–2020 put Perth's mean cloud cover at 47%, from 33% in January to 60% in July.
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