South-facing is the answer most people expect when they ask about roof orientation, and it is often the best single orientation. It is rarely the whole story, particularly on a property with more than one roof face or with anything nearby that casts a shadow.
Orientation sets a curve, not a cut-off
A south-facing array generates the most total energy over a day, with a curve peaked around midday. East and west orientations generate less in total but spread that generation earlier or later in the day.
For a property whose demand is spread across the morning and afternoon rather than concentrated at midday, an east-west split can sometimes suit the building better than a single south-facing array, even though its total output is lower.
Pitch interacts with orientation
The angle of the roof changes how much any given orientation actually receives. A shallow pitch is more forgiving of orientation away from south; a steep pitch rewards getting the orientation right and penalises getting it wrong.
Shading is usually the bigger factor
A well-oriented roof with a chimney, a neighbouring building or a mature tree casting a shadow across part of the array for part of the day can underperform a modestly-oriented roof with a clear view of the sky.
Shading also changes seasonally. A tree that is bare in winter and full in summer, or a low winter sun that clears an obstruction a taller summer sun does not, both need to be assessed across the year, not on a single site visit.
Multiple roof faces are common, not exceptional
Many properties, particularly villas and townhouses, have more than one usable roof face. Splitting the array across them, with separate strings or micro-inverters where appropriate, is often the practical answer rather than trying to force everything onto the single best-oriented section.
What a site assessment actually checks
A useful orientation assessment goes beyond a compass reading:
- Compass orientation of every usable roof face
- Pitch of each face
- Shading from nearby structures and vegetation, across the seasons
- Whether splitting the array across faces suits the property's demand pattern
Related: Residential Solar
This article is general, technical background written for the Solara Energy demonstration website. It is not project-specific advice.
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