On a flat roof, modules can be freely oriented – and the question is usually East-West versus South. South brings the highest yield per module, but a narrow midday peak. East-West brings slightly less per module, but more modules fit on the roof and the electricity is distributed throughout the day. For self-consumption, this is usually the smarter choice today. (As of: July 2026)
Key points in brief
- On the flat roof, modules are elevated – the orientation can be chosen freely, unlike on a pitched roof.
- South orientation: highest yield per module, but steep midday peak and larger row spacing.
- East-West orientation: flatter elevation, smaller spacing, more modules on the roof – yield distributed over the day.
- For self-consumption, electricity distributed throughout the day often counts for more than the pure midday peak.
- What counts is the yield of the entire roof, not that of the individual module – and this is where East-West is often ahead.
Why is orientation on the flat roof a question at all?
On a pitched roof, the roof area dictates the orientation – the modules follow what the roof provides. The flat roof does not have this specification: here the modules are placed on a substructure, elevated, and this elevation can be done in any direction and at almost any angle. From this freedom arises the decision that does not exist in this way on the pitched roof.
Two concepts are opposed to each other: the classic South orientation, in which all modules point south, and the East-West orientation, in which the modules are set up in two directions – one catching the morning sun, the other the evening sun. Both have their logic, and which one wins depends less on the textbook than on your electricity consumption.
South orientation: the highest peak
South-facing modules, elevated at the optimal angle, deliver the highest yield – calculated per module. This is the reason why South was long considered the measure of all things: anyone who wants to get the maximum annual production out of a single module points it south.
The catch becomes apparent when you look from the individual module to the entire roof. South-elevated rows cast shadows backwards – the next row must be far enough away, otherwise it shades itself. On the limited flat roof, this means: larger row spacing, fewer modules overall. And the yield delivered by the South system is concentrated around midday – a steep peak, often exactly when there is the least going on in the household.
East-West orientation: more modules, distributed electricity
With East-West elevation, the modules are flatter and inclined in both directions – one half catches the morning sun, the other the evening sun. Two effects follow from this arrangement, which together tip the scales.
First, the area: Flatter elevated modules cast shorter shadows, the rows move closer together, more modules fit on the same roof. What the individual module delivers less of is often compensated for by the larger number.
Second, the daily distribution: Instead of a narrow midday peak, the East-West system delivers a broader yield – mornings from the east, evenings from the west. It is exactly during these times that consumption falls in many households: breakfast and after work. And for self-consumption, electricity that comes at the right time is worth more than that which pushes into the grid at the midday peak – why self-consumption counts so much is derived in detail elsewhere.
The comparison at a glance
| South orientation | East-West orientation | |
|---|---|---|
| Yield per module | highest | slightly lower |
| Modules per roof area | fewer (large row spacing) | more (small spacing) |
| Daily course | steep midday peak | distributed over morning and evening |
| Self-consumption | Peak often during absence | hits morning and evening consumption |
| Elevation | steeper | flatter |
Simplified comparison, as of: July 2026. Decisive is the planning on the specific roof with a real consumption profile.
What does that mean for your roof?
The honest answer starts with a counter-question: What do you want to do with the electricity? Anyone who consumes as much as possible themselves – heat pump, e-car, someone at home during the day – benefits from the distributed East-West yield and the larger number of modules. That is why East-West is often the obvious choice on modern flat roofs of single-family homes today.
However, there are still cases for South: a small roof where every module counts and the area is not the bottleneck; a consumption profile with a pronounced midday load; or the combination with a battery, which shifts the peak into the evening anyway. And last but not least, the real conditions play a role in the decision – shading by superstructures, the statics of the elevation and the wind loads on the flat roof. How strongly orientation and inclination generally influence the yield is detailed in the guide to orientation and inclination; whether your specific roof is suitable is shown by a look at sonnendach.ch.
The widespread rule of thumb from practice: On a flat roof with limited space and the goal of high self-consumption, East-West usually wins. Where space is plentiful and the midday peak matches consumption, South remains in the running. Ultimately, the calculation is made on the specific roof – not just by compass direction.
On flat roofs, we almost always experience the East-West question as an aha moment: most homeowners enter the conversation with «South is best» – that is what they have learned, and for the individual module it is also true. We then shift the perspective from the module to the entire roof: on a typical flat roof area, we can accommodate noticeably more modules with the East-West elevation because the rows can be closer together. And the electricity comes in the morning and evening – when people shower, cook and charge the car – instead of in a midday peak that nobody at home uses. That almost always convinces in the end. The exceptions are the small flat roofs, where every square metre counts and South gets the last drop out. But the reflex «always South» comes from the pitched roof – on the flat roof it pays to recalculate.
Frequently asked questions
Doesn't East-West bring less yield than South?
Per module yes, calculated for the whole roof often no: Because flatter elevated East-West rows can stand closer together, more modules fit on the same roof. The lower yield per module is partly or fully compensated for by the larger number – and the distributed electricity better matches consumption.
Which orientation is better for self-consumption?
Usually East-West. The yield is distributed over the morning and evening – exactly the times when many households consume the most. The narrow midday peak of the South system, on the other hand, often falls during absence and is fed in instead of used yourself.
Why do South rows need larger spacing?
Because they are elevated steeper and thus cast longer shadows backwards. To prevent one row from shading the next, the spacing must be larger – this costs space and thus modules. East-West modules are flatter, cast shorter shadows and move closer together.
Can I also mix South AND East-West on the flat roof?
In principle, much is possible, but rarely sensible: a uniform orientation simplifies planning, elevation and cabling. A clear decision based on roof size and consumption profile – made by a specialist company on site – is usually more sensible than mixed forms.
Does the inclination play a role on the flat roof?
Yes – the elevation dictates the angle, and this influences yield and row spacing. Flatter angles mean less yield per module, but narrower rows and smaller wind attack surface; steeper angles the opposite. The optimisation of this interaction is part of the planning.
Free initial consultation
Which orientation gets the most out of your flat roof?
We plan the elevation according to your roof area and your consumption – and specifically calculate East-West against South, instead of deciding by rule of thumb.
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Sources: Swissolar (planning principles for flat roofs); empirical values from the planning and installation practice of ecoEn GmbH, Zurich region.
Last updated: 9 July 2026 · Author: ecoEn editorial team
