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Switzerland's solar mandate in 2026: How your canton differs from federal rules

Switzerland's solar mandate in 2026: How your canton differs from federal rules

Ivan Miric·

Since 2024, Switzerland has a nationwide solar mandate for new buildings above 300 m² of building area. At least 50 % of the usable roof must be covered with photovoltaics or solar thermal.

That is the floor. Several cantons go further, and a few tightening rules came into force in 2026 that builders keep missing.

Lucerne: no threshold, renovations included

Lucerne is the strictest case. Across the canton:

  • Every new building, regardless of footprint
  • 50 % of usable roof area on new construction
  • 25 % on renovations, federal law does not require this

If you are renovating a roof in Lucerne, the solar question is on the table from day one.

Aargau: leaflet 26a sets the practice

In September 2025 Aargau revised its leaflet on the "duty to use solar energy". It spells out how usable roof area is calculated, the available exemptions (heritage protection, structurally unsuitable, uneconomic), and how proof is delivered with the building permit.

Zurich, Bern, Basel-Stadt: federal floor plus climate ambitions

Zurich, Bern and Basel-Stadt mostly stick to the 300 m² threshold but push harder on heating replacement and value-added levies. Combined with the federal Mantelerlass, many owners voluntarily oversize systems, the economics improved sharply in 2026.

French- and Italian-speaking cantons: their own routes

Geneva has its own mandate via the cantonal climate law. Vaud anchors its rules in the cantonal energy ordinance. Ticino is close to federal but adds requirements for public buildings.

The exact rule depends on canton, building type and project. Before filing the permit, call the cantonal energy office.

What it means in practice

Three points for your project:

  • Plan early. Structure, shading and the self-consumption concept belong in the pre-design phase, not in construction.
  • More is usually cheaper. If you are building anyway, ask "how much PV fits on this roof?", not "how little will pass". The marginal cost per kWp drops fast.
  • Self-consumption is the lever. With a battery, heat pump and wallbox you reach 70 %+, and the rest is now backed by a federal minimum tariff in 2026.

Free State designs systems canton by canton and handles coordination with the building authority. Under SolarFree we fund the install, you meet the mandate without putting capital down.

Get a free assessment for your project.

Sources: Energiestadt, cantonal energy offices, Swissolar, Federal Office for Spatial Development ARE. As of April 2026. Information without guarantee.