How many hours of direct sun does my garden get?
Full sun, partial shade or shade: hours behind fences and walls of different heights, by season.
The numbers
Hours of direct sun on a wall, by the way it faces
A wall is in the sun when the sun is above the horizon and in front of it, within 90° of the direction it faces. These are the hours for an unobstructed wall; trees and neighbours can only take some of them away.
| Wall faces | 21 June | 20 March | 21 December |
|---|---|---|---|
| North | 7.2 h | 0.1 h | 0 h |
| North-east | 6.5 h | 3.5 h | 0.5 h |
| East | 8.3 h | 6.0 h | 3.8 h |
| South-east | 10.0 h | 8.6 h | 7.2 h |
| South | 9.3 h | 12.0 h | 7.8 h |
| South-west | 10.0 h | 8.6 h | 7.3 h |
| West | 8.3 h | 6.1 h | 3.9 h |
| North-west | 6.5 h | 3.5 h | 0.6 h |
| Wall faces | 21 June | 20 March | 21 December |
|---|---|---|---|
| North | 7.1 h | 0.2 h | 0 h |
| North-east | 6.3 h | 3.9 h | 1.3 h |
| East | 7.5 h | 6.1 h | 4.6 h |
| South-east | 8.6 h | 8.3 h | 7.8 h |
| South | 7.9 h | 12.0 h | 9.2 h |
| South-west | 8.7 h | 8.3 h | 7.8 h |
| West | 7.5 h | 6.1 h | 4.6 h |
| North-west | 6.4 h | 3.9 h | 1.3 h |
What each direction is like
Reading the tables
- South gets the most sun over the year and nearly all the winter sun: in December the sun never leaves the southern sky. In summer, though, the sun rises and sets north of east and west, so a south wall loses the early morning and the evening. What it gets is high and steep, which is easy to shade.
- North gets no direct sun at all from the September equinox to the March one, but in June it catches the sun early in the morning and late in the evening, seven hours in total. That low sun reaches deep into a room.
- East gets the morning all year. Bedrooms and breakfast rooms often face east for that reason; in summer the sun is already in the room before five in London.
- West gets the afternoon and evening, and that is the overheating risk: on a summer evening the sun is low, the air is already warm, and the rays come almost straight through a west window. Low sun is also the hardest to shade with an overhang.
- South-east and south-west get the most hours in summer and almost as many as south in winter: a good compromise for a living room or a balcony.
In the southern hemisphere swap north and south: in Sydney or Cape Town the north-facing wall and garden are the sunny ones.
Passive solar design
How a roof overhang keeps summer sun out and lets winter sun in
The difference between the summer and the winter sun is mostly height. At noon in London the sun stands 62° high in June and only 15° in December. A horizontal overhang above a south window uses that difference: at noon it shades the wall below it to a depth of the overhang times the tangent of the sun’s elevation.
| Date | Sun elevation | Shaded below the overhang |
|---|---|---|
| 21 June | 61.9° | 1.13 m |
| 20 March | 38.4° | 0.48 m |
| 21 December | 15.1° | 0.16 m |
A modest overhang therefore shades most of a window in summer and almost none of it in winter, when the warmth is welcome. It works only on south-facing walls (north-facing in the southern hemisphere): east and west windows meet a low sun in the morning and evening of every season, and need vertical fins, external blinds or trees instead.
Outside
Gardens and balconies
For a garden the question is what stands to its sunny side. A garden on the south side of a house is in the open all day; a garden on the north side sits in the house’s shadow for much of the year, and in December in London a two-storey house shades the ground for about 20 metres behind it. How many hours of sun your garden gets works this out for fences and walls of different heights.
A balcony behaves like a short wall with a roof: the balcony above shades it in summer just as an overhang would, so a south balcony is pleasant at midday in June, while a west balcony gets the full evening sun.
Before you decide
Beyond the compass
Hours of sun are only half the story: the local climate decides whether you want more or less of them, and the buildings and trees around a plot decide how many you actually get. On the sun position map you can place a building or a tree, set its height and see its shadow move through the day and the year, and the sun-hours layer colours every spot by the hours of direct sun it receives.
Keep reading
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