Background
#In 2026, the Valais PV solar obligation mainly concerns new buildings, extensions and certain roof renovations: the cantonal Energy Act generally requires at least 20 W per m² of energy reference area, without allowing more than 30 kW to be prescribed.
If the roof covering is removed on an existing building, 20 W/m² and no more than 80% of the affected roof area become relevant limits. For roof areas above 500 m², on-site electricity generation must be established within 25 years if average annual solar irradiation exceeds 1,200 kWh/m². The cantonal energy office names exemptions such as GEAK class C after renovation, simultaneous facade renovation and renewal of only the north-facing roof; the specific classification follows the cantonal Energy Act, Energy Ordinance and EN-VS-104 energy proof.
What roof and planning dictate
#The project trigger determines the rule: for new buildings and extensions, Art. 33 of the cantonal Energy Act requires at least 20 W/m² of energy reference area; more than 30 kW cannot be required. Under the cantonal page, an extension below 50 m² of energy reference area or below 20% of the existing area, but not exceeding 1,000 m², is exempt.
Removing the roof covering on an existing building triggers a separate obligation under Art. 43 of the cantonal Energy Act and Art. 64 of the Energy Ordinance. The target is at least 20 W/m² of energy reference area and no more than 30 kW; the module area need not exceed 80% of the roof surfaces whose covering is removed.
For roof areas above 500 m², installed capacity is not the only criterion. The building must generate its own electricity within 25 years of the cantonal Energy Act taking effect; only roof surfaces with average annual solar irradiation above 1,200 kWh/m² are mandatory. The requirement is met with at least 40% of the roof area or at least 20 W/m² of energy reference area.
Solar irradiation at the actual site limits the obligation. The Valais energy office points to map.geo.admin.ch for annual irradiation; for roof areas above 500 m², surfaces with average irradiation of no more than 1,200 kWh/m² do not have to be equipped.
An on-site system is not the only statutory compliance route. The Valais energy portal names equivalent production through financial participation in a renewable installation in the canton or a neighbouring canton, or through a self-consumption grouping. This alternative must be documented specifically in the project and proof planning.
An economic exemption is not an automatic waiver. According to the Valais energy page, the mandatory part will generally not qualify for a disproportionality exemption if generation costs are 25 centimes/kWh or lower; above that level, the case is assessed individually under Art. 5 of the Energy Act and Art. 5 of the Energy Ordinance.
The process in six steps
#Tick off for your project
Record the project trigger
before requesting a quote, determine whether the project is a new building, an extension, removal of the roof covering or an existing building with more than 500 m² of roof area. These four cases use different reference values and periods in Valais under Arts. 33 and 43 of the Energy Act.
Measure the energy reference area and roof surfaces
document the energy reference area for a new building or extension; for roof renovation, record the roof area actually stripped; above 500 m², separate the relevant partial surfaces as well. Without these areas, the 20 W/m² or 40% requirement cannot be determined reliably.
Check irradiation and exemptions
for large roofs, compare average annual irradiation using map.geo.admin.ch. Then document GEAK class C after renovation, simultaneous facade renovation, north-facing roof renewal and seasonal-only use as possible exemptions.
Choose the compliance route
size the PV quantity under the 20 W/m², 30 kW, 80% or 500 m² rule, or assess an allowed alternative through financial participation or a self-consumption grouping. For an alternative, the location, participation and equivalence must be traceable in the energy proof.
Prepare EN-VS-104 and the economic assessment
the Valais energy office provides the EN-VS-104 energy proof and implementation guidance. If economic disproportionality is claimed, document the generation costs of the mandatory part; 25 centimes/kWh or lower is generally not sufficient for an exemption.
Coordinate the building and energy procedures
the selected system, alternative or exemption must match the building-application documents and energy proof. For the specific parcel, the municipality, the Energy Office and, for permit questions, the Cantonal Building Commission are decisive; a PV quote alone does not replace the proof.
Checked for your roof, not just read up on
Once the framing is clear, a property-specific check with roof, grid and documentation is worthwhile.
Frequently asked questions
#Sources
#The responsible authorities are decisive. Always verify binding details – amounts, deadlines and conditions – for your specific property against the current status of the respective authority.