Since 2025, installing solar panels is no longer always a choice: it is an obligation for certain buildings. The federal electricity law requires photovoltaics on large new constructions, and the cantons' new energy model (MoPEC 2025) extends the requirement to roof renovations. Here is who is affected, and from when.
The federal obligation: large new buildings
The federal electricity law came into force in stages, on 1 January 2025 and then 1 January 2026. It requires a photovoltaic installation for any new construction — or complete renovation — whose floor area exceeds 300 m².
In practical terms:
- the collector area must cover at least 40 % of the building's determining area;
- the installation may be placed on the roof, the façade, or both;
- the solar electricity fed back into the grid is remunerated at a guaranteed minimum price throughout Switzerland.
For a standard detached house, the 300 m² threshold is generally not reached. The federal obligation mainly targets apartment blocks, commercial buildings and large constructions.
The MoPEC 2025: solar comes to roof renovations
The MoPEC (the cantons' model energy regulations) is the reference text that the cantons incorporate into their own energy law. Its 5th edition, the MoPEC 2025, was adopted by the Conference of Cantonal Energy Directors at the end of August 2025.
Key change for existing owners: the photovoltaic production obligation is extended to roof renovations. As soon as a canton has transposed it, redoing the covering or the waterproofing of a roof over at least 50 m² triggers the obligation to install solar.
New build, renovation, replacement: who is affected?
New construction larger than 300 m²
Federal solar obligation, in force. Photovoltaics is part of the project from the design stage.
Roof renovation larger than 50 m²
Obligation arising from the MoPEC 2025, applicable as soon as your canton has adopted it. Plan for solar when you redo the roof covering.
Replacing a fossil-fuel heating system
The MoPEC 2025 then requires a renewable-energy system — a separate topic, covered in detail in our dedicated guide.
A constraint, but also support
The solar obligation often goes hand in hand with subsidies: the Buildings Programme and several cantons support photovoltaics and energy renovation. Before giving up on a project because of the cost, it is worth estimating the available support with our subsidy calculator.
One prior question remains: are your roof and your plot suited to an extension or an added storey that would make the installation pay off? The zone, the utilisation index and the building envelope determine what you can add — well beyond the solar question alone. That is exactly what a plot report sets out in black and white, backed by official sources, before you engage an architect.