Collective Solar Self-Consumption in Catalan Apartment Buildings: CAU, Sharing Agreements andR甲

Before accepting a quotation for shared solar panels, an owners’ association should decide who will use the electricity, which supply points will participate, the proposed generating capacity and how production will be allocated. It should also establish who will coordinate the CAU self-consumption code, municipal procedure, technical documentation, Catalan Self-Consumption Register and communications with the distribution company and electricity suppliers.

A completed installation is not necessarily electrically legalised, and RAC registration does not necessarily mean that shared generation is already appearing on every participant’s bill. Collective self-consumption combines an owners’ decision, municipal planning or works formalities, electrical and generation procedures before the Generalitat de Catalunya, and the subsequent association of participating electricity contracts. The exact route can vary with the installation, municipality and distribution company.

When is rooftop solar collective self-consumption?

Collective self-consumption exists when several consumers receive allocated energy from a nearby, associated generating installation. If rooftop panels supply only the lift, corridor lighting and other communal services through one CUPS supply-point code, the arrangement is administratively individual self-consumption. The same applies where only one flat or commercial unit is supplied, even though the panels occupy a communal roof. Several supplies—such as homes, business premises and communal services—must be associated for the arrangement to be collective. [3]

Before approving the work, assess available roof area, orientation, shading, structural condition and access for installation and maintenance. Check whether the property is listed or affected by planning restrictions and whether existing building services could be disturbed. The feasibility study should also examine participants’ consumption patterns, proposed capacity, whether the system will export surplus electricity and whether simplified surplus compensation is available.

The proposal should identify the installation owner, participating supplies, maintenance arrangements and a procedure for later additions, withdrawals or account-holder changes. Collective systems require a meter recording total generation; individual meters continue to measure each supply’s consumption. Photovoltaic installations up to 100 kW may use simplified surplus compensation when all applicable conditions are met, but compensation for exported energy cannot make the compensated energy component of the bill negative. [3]

• Inspect the roof, structure, shading and safe maintenance access.
• Identify planning restrictions, heritage protection and affected services.
• Collect the CUPS and current account-holder details for each participant.
• Compare generation with participants’ hourly consumption where data are available.
• Define capacity, ownership, export arrangements and maintenance responsibilities.

Building approval and the energy sharing agreement

The owners’ resolution concerning the communal roof and the energy sharing agreement serve different purposes. The former authorises work on a common element and records the association’s internal conditions. For renewable systems on common elements without exclusive use, ICAEN states that approval may be given by a simple majority of owners participating in the vote, provided they also represent a simple majority of the ownership shares present or represented. The building administrator or legal adviser should confirm how Catalan civil law applies to the particular proposal. [3]

The separate sharing agreement identifies every associated consumer and assigns each one an allocation coefficient, usually called beta or β. All participants must sign it. For every hour in the billing period, their coefficients must add up to one. Coefficients may remain constant or vary by hour; hourly variable allocation requires a text file prepared in accordance with the technical specifications under Royal Decree 244/2019. [5]

An association might base allocation on financial contributions, expected consumption, agreed percentages, time-of-use patterns or a combination of factors. There is no single formula suitable for every Barcelona apartment building, so modelling alternatives before signature can reduce avoidable mismatches between production and demand. The internal agreement should also address how future changes will be approved, while recognising that changing participants or coefficients may require renewed submissions to the relevant market agents.

• Community resolution: authorises the work and conditions for using the communal roof.
• Sharing agreement: identifies participating consumers and their allocation coefficients.
• CAU: the unique code connecting the collective arrangement’s generation and consumption points.
• CUPS: the unique identifier belonging to each participating electricity supply point.
• CIL: the production installation’s settlement identifier, where applicable; it is not the CAU or CUPS.

Technical documents and the usual administrative sequence

For the Catalan procedure covering self-consumption with surplus compensation, an installation up to 10 kW requires a technical design report, commonly called a memoria técnica. Above 10 kW, a technical project signed by a competent professional is required. Files requiring a project also provide for the relevant works supervision and completion certificate. Separate structural calculations or supporting documents may still be necessary because of roof condition, heritage controls, work at height or other affected installations. [2]

A practical sequence is to define participants, capacity and operating mode; assess the roof; secure the owners’ approval; and prepare the design report or project. The relevant municipal works procedure then needs attention, normally through prior notification for photovoltaic installations in Catalonia, subject to exceptions that must be checked with the local council. For installations with exports on developed land, systems up to 15 kW are exempt from an access and connection permit, whereas those above 15 kW and up to 100 kW require it under the cited Catalan procedure. [2] [3]

The CAU should be obtained through the applicable distribution-company process, after which the system is installed and certified. Before requesting operating authorisation and RAC registration, the corresponding low-voltage responsible declaration must be filed. The generation file, signed sharing agreement and coefficient file can then be completed, followed by checks on activation for each contract. This is an indicative sequence rather than a universal guarantee: consult the current Generalitat, council and distribution-company instructions. [2] [4]

• Define consumers, proposed allocation, capacity and export arrangements.
• Commission the roof assessment and technical report or project.
• Complete the applicable municipal and grid-access procedures.
• Obtain the CAU, install and certify the system.
• File the low-voltage declaration before completing generation and RAC formalities.

CAU, RAC and the documents the community should retain

Good document control begins before installation. Keep the tax identification details of the association or installation owner, proof of representation, the certified community resolution and a list of current participants, CUPS codes and account holders. The technical file should contain the design report or project, electrical installation certificate and, where applicable, the works supervision and completion certificate. Municipal documents and any required access and connection records should also be retained.

The CAU, or Código de Autoconsumo, uniquely identifies the self-consumption arrangement and connects its associated generation and consumption points. One collective arrangement has one CAU, not a separate code for every neighbour. RAC means Registre d’Autoconsum de Catalunya, the Catalan Self-Consumption Register. Following successful completion of the procedure, the Generalitat registers the installation, and the RAC number appears in the registration document or relevant resolution. These identifiers are not interchangeable with one another or with each participant’s CUPS. [4]

The association should also retain the signed sharing agreement, the validated coefficient file and evidence that the required information was sent to the relevant agents. The distribution company handles metering and allocation data, while participants’ electricity suppliers apply the resulting arrangements to their contracts and bills. Consequently, RAC registration does not replace the communications required to activate collective self-consumption across every associated supply. [2] [5]

• Community resolution and evidence of the representative’s authority.
• Participant list with names, current account holders and CUPS codes.
• Technical report or project, electrical certificate and completion documents.
• CAU, low-voltage declaration and RAC registration document.
• Signed sharing agreement, coefficient file and submission records.

Costs, timescale and troubleshooting missing bill credits

The Generalitat currently lists its procedure for compensated self-consumption installations up to 100 kW as free of charge. This does not mean the overall project is free: municipal charges, technical design, structural calculations, installation work, inspections and professional administration may all involve costs. There is no single official price covering these items across Catalonia, so obtain an itemised quotation and check current local charges directly with the relevant council. [2]

For the cited procedure, the Generalitat publishes a maximum period of three months to check the submitted information. This is an administrative maximum, not a promised total project duration or a guarantee that every bill will be updated within that period. Municipal processing, correction requests, distribution-company actions and individual suppliers may follow different schedules. Fees, forms and published timescales can change and should always be verified on the official websites before filing. [2]

If the panels are producing electricity but no allocation or compensation appears on bills, trace the entire documentary chain. Confirm the electrical certificate, low-voltage declaration, RAC registration and unique CAU. Then compare every CUPS and account holder against the current contracts, confirm that all associated consumers signed the same sharing agreement, and verify that coefficients total one for every hour. Finally, obtain evidence that the distribution company and each supplier received and processed the information. [2] [4] [5]

• Compare the declared owner, capacity and electrical arrangement across all documents.
• Download the RAC evidence and locate the RAC registration number.
• Check the single CAU and every associated CUPS for transcription errors.
• Review signatures, file format and coefficient totals.
• Inspect each participant’s contract and bills rather than relying on one sample.

Frequently asked questions

Must every owner in the building participate?

Not necessarily. Collective self-consumption requires several associated consumers, but it does not require every property owner to become a participant. The association must approve the use of the common element under the applicable rules. The owners involved in that decision should not be confused with the consumers who join and sign the energy sharing agreement.

Can another resident join or can the coefficients change later?

Changes may be possible, but amending an internal spreadsheet is not sufficient. The association must review the signed sharing agreement, allocation coefficients and communications to the distribution company and suppliers. It should also establish whether registered information or individual contracts must change. Confirm the current procedure with the relevant agents before approving an alteration.

Is the RAC number the same as the CAU?

No. The CAU uniquely identifies the self-consumption arrangement and links generation with associated consumption points. The RAC number identifies its entry in the Catalan Self-Consumption Register. Each participating supply retains its own CUPS, while the CIL is a separate identifier used for the production installation where applicable.