The Core Challenge for Condominium Solar
In Switzerland, Stockwerkeigentum (condominium or strata ownership) is a form of property right where each owner holds an individual unit plus a proportional share of the common elements — including the roof. This means no single owner can unilaterally install a solar system on the communal roof. Any change to the common parts requires a collective decision by the Stockwerkeigentümergemeinschaft (STWEG — the owners' association).
This is the central hurdle: getting enough owners aligned on a decision that requires upfront cost, shared governance, and a long-term commitment.
What Vote Is Required?
Swiss property law (Zivilgesetzbuch, ZGB Art. 712g) distinguishes between administrative decisions and significant alterations:
- Ordinary administration (e.g., repairing the existing roof): simple majority
- Larger renovation or new installation (solar on the communal roof): this typically falls under nützliche Verwendungen (useful improvements), requiring a qualified majority — usually at least two-thirds of all co-owners representing at least two-thirds of the share value (Wertquoten)
- Check your building's Gemeinschaftsordnung (the STWEG's own constitution): some buildings set higher thresholds; others explicitly enable solar with a simple majority as part of an energy clause
Minority owners cannot block a qualified majority vote — but minority owners also cannot be forced to contribute financially to improvements that only benefit others (see the ZEV financial structure below).
Setting Up a ZEV in a Condominium Building
The Zusammenschluss zum Eigenverbrauch (ZEV) framework is the legal mechanism that enables solar sharing among multiple parties in a Swiss building. For the foundational mechanics — eligibility, sub-metering, internal billing — see our full ZEV guide for apartment buildings. For a Stockwerkeigentum:
Who can participate?
Participation in the ZEV is voluntary for individual unit owners. An owner who votes against the installation or simply does not wish to participate remains on the standard grid connection and continues paying normal tariffs to the Verteilnetzbetreiber (VNB).
→ Your bill, your roof, your result — find out your solar savings now.
Who acts as ZEV operator?
The STWEG itself, or a delegated committee member, typically acts as the ZEV operator. This role involves:
- Internal metering and billing for ZEV members
- Managing grid export remuneration
- Coordinating maintenance costs
Some STWEG communities appoint a professional energy management company (e.g., Energie Service Biel/Bienne or a building manager with energy experience) to handle the operational complexity.
ZEV financial model in a condominium
| Item | Funded by | Notes |
|---|---|---|
| Solar installation cost | ZEV participants (proportionally) | Non-participants do not contribute |
| Pronovo EIV rebate | STWEG as system owner | Rebate credited against installation cost |
| Electricity sold internally | ZEV operator bills participants | At rate below standard grid tariff |
| Grid export income | STWEG / ZEV operator | Distributed per participation share |
| Maintenance costs | ZEV participants | Allocated by participation share |
Step-by-Step: From Proposal to Operation
Initiate the proposal: one or more co-owners bring a solar/ZEV motion to the annual STWEG assembly. Commission an initial feasibility assessment from a Solarprofi-labelled installer.
Obtain a detailed quote and yield simulation: a Polysun report showing predicted yield, self-consumption rate, and indicative ZEV electricity price for participants.
Draft the ZEV agreement: with a lawyer or energy adviser familiar with Swiss condominium law, draft the internal ZEV rules (pricing, cost allocation, exit terms, what happens on unit sale).
Vote at the STWEG assembly: present the full package — costs, benefits, ZEV agreement, Pronovo rebate, and cantonal bonuses. Aim for the required qualified majority.
Register the ZEV with the VNB: before installation begins, notify the local grid operator of the planned ZEV.
Install and commission: the chosen installer completes the installation, sub-meters all participating units.
Register with Pronovo: submit the EIV application within three months of commissioning.
Begin ZEV billing: monthly statements to ZEV participants at the internally agreed rate.
→ Still unsure if the maths add up? Check your personal payback period — it takes 60 seconds.
What Happens When a ZEV Participant Sells Their Flat?
This is one of the most frequently asked questions. The ZEV agreement should include explicit provisions:
- The new owner typically assumes the selling owner's ZEV participation
- Sellers must disclose the ZEV obligation in the property sale documentation
- A defined exit option (with a notice period and any exit costs) protects new owners who do not wish to participate
Absent clear terms, a unit sale can create disputes — so legal drafting at the start is essential.