With on-roof mounting, the modules are fixed on a substructure above the existing roof covering – that is the standard and the cheaper variant. With in-roof mounting, the modules replace the roof skin and sit flush in the roof surface. In-roof costs more but convinces visually and pays off above all when a roof renovation is due anyway.
Key points in brief
- On-roof is the normal case: proven, cheaper, possible on practically any intact roof.
- In-roof integrates the modules into the roof surface and at the same time takes over its function as the roof skin.
- The greatest advantage of in-roof is the look – for many the decisive reason.
- In-roof becomes economically interesting when the roof covering and the solar system are renewed in one go.
- With regard to watertightness, in-roof has higher requirements for execution.
How do the two mounting types differ?
The difference lies in the relationship of the modules to the roof. With on-roof mounting the existing covering – tiles, fibre cement, sheet metal – remains fully in place. On top of it comes a substructure to which the modules are mounted a few centimetres above the roof surface. The roof keeps its function, the system sits above it.
With in-roof mounting, tiles or other covering are removed where the modules go. The modules move into the roof plane and there take on the task of the roof skin themselves: they drain rain and protect against the weather. The result is a smooth, flush surface without modules mounted on top.
| Feature | On-roof | In-roof |
|---|---|---|
| Roofing | remains in place | is replaced |
| Appearance | modules sit raised on top | flush in the roof surface |
| Costs per kWp | lower | higher |
| Rear ventilation | very good | more limited |
| Ideal for | intact roof | new build or roof renovation |
Simplified overview, as of: July 2026. Concrete suitability depends on roof, covering and condition.
Why is on-roof the standard?
Because it's the right answer for the great majority of roofs. On-roof can be implemented on any intact roof without touching the covering. The installation effort is lower, the systems are mature, and the modules are well ventilated from behind – which benefits output, because cooler modules deliver more (the connection is in the article Heat & output).
In short: if your roof is in order and no renovation is due in the next few years, on-roof is almost always the economically sensible choice. The price difference to in-roof can't be justified by anything going beyond looks.
When does in-roof pay off?
In-roof plays out its strengths in two situations:
In a new build. Here the roof skin is being newly created anyway – planning the modules as the covering is an architecturally clean route. The roof looks all of a piece, without technology mounted on top.
In a roof renovation. If the covering is due for renewal due to age, the calculation shifts. Because part of the costs that make in-roof more expensive arise in a renovation anyway: tiles and plumbing work you would otherwise pay for separately are partly saved. Anyone who thinks of roof and solar system together gets more out of both budgets – the article Combining roof renovation & PV works this out.
Then there is the factor that is hard to put a figure on but is real: the look. Where an inconspicuous solution integrated into the roof surface is wanted – for design reasons or because of requirements in protected zones – in-roof is often the only accepted variant. Related here is the topic of solar tiles, which take this integration idea even further.
What must be considered technically with in-roof?
Because with in-roof the modules replace the roof skin, watertightness is the decisive question. The system must reliably drain rain and must not let moisture under the modules even in driving rain or snowmelt. That is well solvable with proven in-roof systems – but it forgives poor execution less than an on-roof system, where the actual roof lies underneath anyway.
Second point: rear ventilation. In-roof modules sit closer to the roof structure, the air circulation behind them is lower than with on-roof. In practice the yield difference turns out moderate, but belongs in honest planning. Good in-roof systems take ventilation into account in their construction.
Both lead to the same conclusion: in-roof is not a do-it-yourself topic and belongs in the hands of a company that knows the system. What makes up a system in general is shown in the overview All components explained.
How big is the cost difference?
In-roof lies above a comparable on-roof system per kilowatt – the premium arises from the more elaborate system and the higher demands on installation. How large the difference turns out depends strongly on roof and system; a blanket figure would be unreliable. What matters is the right reference point: with a roof renovation coming up, you don't compare on-roof against in-roof, but renovation plus on-roof against in-roof as a combined solution. In that calculation the gap shrinks markedly. The details in the cost comparison: In-roof or on-roof – the costs.
The question of in-roof or on-roof is decided in our projects almost never on technology, but on two other things: the condition of the roof and the building owner's aesthetic expectations. Anyone with an intact roof and no special visual wishes does right with on-roof – anything else would be money for an effect you can hardly see. Anyone who is renovating anyway or values a calm roof appearance may find in-roof the more fitting solution. In the consultation we lay both variants side by side with their real figures instead of selling a philosophy.
Frequently asked questions
Is in-roof or on-roof better?
Neither is better across the board – they solve different situations. On-roof is cheaper and the standard for intact roofs. In-roof convinces visually and pays off above all in a new build or roof renovation, when the covering is renewed anyway.
Does an in-roof system deliver less electricity?
Tendentially a little, because rear ventilation is lower and warmer modules perform minimally less. The difference is moderate in practice and cushioned by good systems in their design – it is not an exclusion criterion.
Can I convert an existing on-roof system to in-roof?
That is uneconomical: it would mean dismantling, a new covering and a different system. The switch practically never pays off for looks alone – the in-roof decision makes sense only if it is made from the start or as part of a renovation.
Is in-roof watertight enough in heavy rain?
Yes, proven in-roof systems are designed to replace the roof skin fully. Professional execution is decisive – here in-roof forgives less carelessness than on-roof, which is why the company's experience counts.
Is in-roof suitable for every roof?
Not without restriction. Roof pitch, covering and construction play a role. On very flat roofs or with certain coverings, on-roof is the better or only choice. The on-site inspection clarifies suitability.
Free initial consultation
In-roof or on-roof for your roof?
We assess your roof, show you both variants with real figures and recommend what suits your situation. Free of charge and without obligation.
Prefer to talk? +41 78 830 83 35
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Swissolar-certified specialist company · ESTI installation authorisation (Art. 14 NIV) · in Zurich since 2017 · over 150 systems completed · a personal answer from the specialist company, no call centre
Sources: EnergieSchweiz, Swissolar, manufacturer documentation.
Last updated: 9 July 2026 · Author: ecoEn editorial team
