Short answer
What you need to know first.
For builders, architects and owners in Aargau who need to know before building application or quote whether their new building falls under the solar obligation and how PV planning interacts with energy proof, permitting and economic assessment.
Important
This page does not replace a property-specific legal or subsidy assessment. The solar obligation in Aargau depends on the concrete building application, chargeable building area, protection requirements and economic viability evidence. The current energy ordinance, responsible municipality and cantonal execution aids are binding.
Decision points
What determines the right path.
The 300 m² threshold is the first determinant: new buildings are affected when the chargeable building area per building application totals more than 300 m². Not only main buildings matter, but also small buildings, extensions and parts of underground structures that project above the relevant terrain and are covered.
The minimum size is area-based: photovoltaic modules and glazed, selectively coated solar thermal absorbers must together reach at least 20 percent of the chargeable building area. Whether this area is implemented on the roof, facade or in combination is a planning question and should not be decided only after the energy proof.
Aargau does not treat technical impossibility as a simple standard exception. The fact sheet assumes that implementation is generally possible when roof and facade areas are considered; economic proportionality therefore becomes the central exemption argument.
Anyone claiming economic disproportionality must provide evidence using the cantonal calculation aid. Relevant factors include amortisation over 25 years or proof that the required energy yield cannot be achieved despite including permissible roof and facade variants.
Townscape and landscape protection can justify an exemption, but not automatically. An exemption is only possible where, based on specialist assessment, the installation is inadmissible in zones with elevated requirements; partial implementations or alternative facade solutions should therefore be considered early.
The solar obligation and the building-law notification procedure are separate topics. The obligation under § 26a EnergieV determines whether solar area must be planned; the solar notification form and permit question determine how the concrete installation is submitted procedurally.
Sequence
How the project stays cleanly managed.
- 1
Calculate building areas in the preliminary project: combine all buildings in one building application and check whether the chargeable building area exceeds 300 m². Splitting simultaneously constructed buildings into several applications should not be planned as an avoidance strategy.
- 2
Derive the minimum solar area: determine the 20 percent requirement from the chargeable building area and check whether roof, facade or a combination of PV and solar thermal can sensibly accommodate the area.
- 3
Coordinate roof and facade planning with the architecture: clarify roof structures, parapets, terraces, railings, access, fire protection, maintenance and shading early so the solar area does not later conflict with ventilation, technical equipment or design.
- 4
Bring energy proof and building submission together: the obligation to use solar energy belongs in the building project documents. Since April 2025, energy proofs in Aargau are submitted electronically via EVEN; PV planning should therefore be consistent with the proof documents.
- 5
Prepare exceptions only with evidence: obtain specialist assessment for protection conflicts; for economic viability use the cantonal calculator with the required standard values. Without traceable evidence, an exemption is not robust.
- 6
Clarify the procedure for the concrete installation separately: in addition to the solar obligation, check whether the planned roof or facade system is subject to notification or a full building permit. This affects timing, documents and the realistic installation start.
Checklist
Questions to settle before the quote.
- Correctly assess new buildings above 300 m² chargeable building area
- Check the 20 percent minimum area and the combination of PV and solar thermal
- Prepare exemption only for protection conflicts or proven economic disproportionality
FAQ