Switzerland has the best winter sun in this set and the tightest door in front of it.
Separating built from unbuilt land is a founding principle of Swiss planning, and a purely private house on green land is not one of the exceptions — on agricultural land you may not even be allowed to buy the parcel.
Where a building already stands lawfully, the sun in a Valais valley is genuinely good and the bill is dominated by labour rather than hardware.
Key number
9%
The share of a typical Swiss single-family rooftop solar bill that is the panels themselves — CHF 2,633 of about CHF 27,750 at autumn 2025 prices. Mounting, DC work and scaffolding are 44%, and planning, administration, inspections and transport another 19%.
Outside the building zone, the default is no
Building outside the building zones runs on the Spatial Planning Act, Articles 16 to 16b, 24 to 24d and 37a, with Articles 33 to 43 of the Ordinance.
The federal spatial development office is explicit: separating built from unbuilt land is a fundamental principle, permits outside the zones carry strict conditions, and they are only effective where the competent cantonal authority grants them or consents in writing by formal decision.
The commune receives the application; the canton decides it.
The exceptions cover uses that require a location outside the zones, and changes to existing lawful buildings — a dwelling on green land is generally only reachable where a genuine farm needs it operationally. The office also warns that unauthorised works create restoration obligations that run for decades and bind later owners, and advises buyers to get documentation that what stands was lawfully built.
Source: Federal Office for Spatial Development, building outside the building zones, citing the Spatial Planning Act and Ordinance
You may not be allowed to buy the land either
Agricultural land is governed by the Federal Act on Rural Land Law.
Acquiring an agricultural holding or parcel needs authorisation under Article 61, and authorisation is generally reserved to a Selbstbewirtschafter — someone who will work the land themselves, with self-cultivation seriously intended and practically possible.
The same act polices price: a price is excessive where it exceeds the five-year average for comparable local land by more than 5%, a margin cantons may raise to at most 15%.
Lex Koller then restricts acquisition by persons abroad. European Union and EFTA nationals lawfully resident in Switzerland are not persons abroad and buy freely; third-country nationals are, and need cantonal authorisation.
Source: Federal Office for Agriculture on rural land law, Article 61 authorisation, self-cultivation and the excessive-price test; cantonal guidance on Lex Koller
The Sicherheitsnachweis
Every low-voltage installation needs a Sicherheitsnachweis, the safety verification required by Article 37 of the Low-Voltage Installations Ordinance (SR 734.27), under the federal inspectorate for heavy current installations. It records the installation, the inspection period and the result of the inspection carried out.
Photovoltaic installations are inside the ordinance where they run at up to 1000 V alternating or 1500 V direct current, which covers domestic arrays, and the verification must carry a measurement and test protocol for photovoltaics. The inspectorate’s Directive 233 requires the current protocol, meeting SN EN 62446-1:2016. None of it depends on a network connection.
Source: Federal Inspectorate for Heavy Current Installations on periodic inspections and safety verifications, Low-Voltage Installations Ordinance SR 734.27 Article 37 and Directive 233
The sun, and the mountain that eats it
PVGIS gives Sion in the Valais 4.34 peak sun hours a day across the year at a 39-degree tilt and 2.12 in December — the strongest December of any site in this set outside the Balkans. Bern runs 4.14 and 1.98. Steepening the Sion array to 60 degrees lifts December from 57.8 to 63.8 kWh per kilowatt-peak while cutting the year from 1,290 to 1,227 kWh.
Altitude does not automatically help, because the skyline gets in the way. At Davos the model with its calculated terrain horizon returns 3.18 peak sun hours across the year and 0.87 in December; with the horizon switched off, 3.29 and 1.13. The ridges cost about a quarter of December output there. In Alpine valleys the horizon profile for the exact coordinates matters more than the altitude on the deed.
Source: PVGIS 5.2, Joint Research Centre, PVGIS-SARAH2 2005–2020, optimal and 60-degree tilt, with and without calculated terrain horizon
What a build costs
A Swiss utility’s 2026 cost guide puts a typical 8 to 10 kWp single-family system on about 50 square metres of roof at CHF 25,000 to 30,000 installed, before subsidy.
Its breakdown at autumn 2025 prices is the useful part: modules CHF 2,633; substructure, mounting, DC installation and scaffolding CHF 12,267; inverter and its installation CHF 2,733; commissioning CHF 1,500; planning, administration, inspections and transport CHF 5,367.
The federal one-off remuneration covers up to around 30% of a qualifying installation, and it is a feed-in-side instrument rather than something a stand-alone system was written for. The electricity being replaced is expensive: the Swiss electricity commission’s 2026 tariffs put a typical household at 27.7 Rappen per kWh, about 1.3 Rappen below 2025, or CHF 1,247 a year on the standard 4,500 kWh profile.
Source: Swiss utility photovoltaic cost guide 2026 with autumn 2025 price breakdown; Swiss Federal Electricity Commission 2026 household tariffs
Water, sewage and the connection obligation
Swiss water protection starts from an obligation to connect. Article 11(2) of the Water Protection Act defines the area of public sewers as the building zones, other areas for which a sewer was built, and further areas where connection is appropriate and reasonable — a test that can reach a property outside the building zone.
Where connection is demonstrably unreasonable, cantonal practice requires wastewater handled to the state of the art: a small treatment plant, or a sealed drainless tank emptied periodically to a central works, approved by the cantonal environment office and in some cantons under a contract recorded in the land register. Composting toilets and greywater are judged inside that cantonal framework.
Source: Cantonal guidance on wastewater disposal outside the building zone under Article 11 of the Water Protection Act
Common questions
Can I build an off-grid house on Swiss farmland?
Generally no. Permits outside the building zones need the cantonal authority's grant or express written consent, and the exceptions cover location-bound uses and existing lawful buildings rather than private houses on green land; a dwelling is usually only reachable where a genuine farm needs it operationally.
Can a foreigner buy the land?
Two filters apply. Rural land law reserves the acquisition of agricultural land to self-cultivators under Article 61 authorisation and caps the price. Lex Koller separately treats third-country nationals as persons abroad needing cantonal authorisation, while European Union and EFTA nationals lawfully and actually resident in Switzerland are not.
Does an off-grid system still need the Sicherheitsnachweis?
Yes. The safety verification under Article 37 of the Low-Voltage Installations Ordinance attaches to the installation, not to a grid connection, and a domestic photovoltaic array operating up to 1000 V AC or 1500 V DC is inside the ordinance, with the photovoltaic measurement and test protocol required alongside it.
Where these figures come from
- PVGIS 5.2, European Commission Joint Research Centre (annual and December peak sun hours and monthly yield per kWp at optimal fixed tilt, PVGIS-SARAH2 2005–2020, 14% system loss, with and without calculated terrain horizon) — read August 2026
- Federal Office for Spatial Development (ARE) — building outside the building zones: legal basis, cantonal consent, and restoration obligations binding later owners — read August 2026
- Federal Inspectorate for Heavy Current Installations (ESTI) — periodic inspections and safety verifications under the Low-Voltage Installations Ordinance SR 734.27 — read August 2026
- Federal Office for Agriculture (BLW) — rural land law: authorisation to acquire agricultural land, self-cultivation, and the excessive-price test — read August 2026
- Swiss Federal Electricity Commission (ElCom) electricity price portal — 2026 household tariffs, 27.7 Rappen per kWh for a typical household — read August 2026
- Swiss utility photovoltaic cost guide 2026 — CHF 25,000–30,000 for 8–10 kWp installed and the autumn 2025 cost breakdown by component — read August 2026
- Canton of Aargau — wastewater disposal outside the building zone: Article 11 of the Water Protection Act, small treatment plants and sealed drainless tanks — read August 2026
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