The anatomy of the paperwork behind a legal installation

The paperwork matters as much as the panels

A self-consumption installation is two jobs at once: the one on the roof and the one on paper. The first can be seen from the street; the second decides whether you can offset your surplus energy, whether you can claim tax deductions, and whether tomorrow you can sell the house with everything in order. Around the area there are immaculate roofs that have been feeding energy into the grid without compensation for a long time, because their file is missing one step.

The order matters, because each document opens the door to the next: without the technical report there is no serious responsible declaration, without the installation certificate there is no legalisation, and without legalisation there is no register and no compensation. That is why we tell the whole story in order, with what the client receives at each milestone and what they should keep.

The initial study and the technical report

Everything starts before anyone climbs onto the roof: the home's real consumption, orientation, shading, the state of the roof and of the electrical panel. From there comes the design and, with it, the technical report: the document that describes the installation exactly as it will be built. For ordinary residential installations, a report signed by a licensed installer is enough; larger installations may require a full project drawn up by a qualified engineer. The report covers, among other things:

What the client receives at this milestone: a copy of the technical report. It is the portrait of their installation and the foundation of everything that follows, so it should always be kept.

• The description of the modules, the inverter and the electrical protections.
• The electrical diagram of the installation and its connection to the home.
• The position of the panels on the roof and the planned cabling.
• The justification of compliance with the applicable regulations.

The town hall: responsible declaration, not a licence (almost always)

In the Valencian Community, since Decree Law 14/2020, today incorporated into the TRLOTUP, rooftop self-consumption installations on urban land are processed through a responsible declaration: the document is filed at the town hall together with the technical documentation, and the work can be carried out under the declarant's responsibility, without waiting for a building licence. The framework is the same in Xàtiva, Canals, Ontinyent or Navarrés, although each town hall has its own forms and fees.

The important exception: listed buildings or those within the protected surroundings of a Site of Cultural Interest. There, a licence or authorisation from the heritage authority may be required, and it pays to know this before buying a single panel. In historic centres like Xàtiva's, it is not a rare case.

What the client receives at this milestone: the filing receipt of the responsible declaration, with its registry stamp. It is the proof that the work was notified where it should be.

The electrical installation certificate and legalisation with Industry

Once the assembly is finished, the licensed installer issues the electrical installation certificate, the CIE, popularly known as the boletín. It is the document certifying that the installation complies with the regulations and that whoever built it answers for it with their signature and their licensed company number.

With the CIE and the technical report, the installation is registered with the Industry department of the Generalitat. That legalisation is what makes the installation officially exist: without it there can be no self-consumption register and no compensation. The work here is to file the complete documentation and follow it up until the registration is done.

What the client receives at this milestone: their copy of the CIE and, later, the proof of registration with Industry. They are two of the most important papers in the whole folder.

The self-consumption register

With the installation legalised comes the entry in the administrative self-consumption register. For residential installations this step builds on the documentation already filed with Industry, but it is worth checking that the registration has actually happened rather than taking it for granted: it is a discreet formality that later proves decisive, because the Valencian regional tax deduction specifically requires the self-consumption register entry and the IVACE certificate in order to be claimed.

What the client receives at this milestone: the reference or proof of entry in the register. An unglamorous piece of paper that is worth money on the tax return.

The distribution company and surplus compensation

In parallel, the local distribution company must be aware of the installation so it can adapt the access contract and so the meter measures in both directions. Once legalisation is complete, the information reaches the distribution company and the supplier can activate the simplified surplus compensation scheme: the energy the roof feeds into the grid is discounted on the bill according to each household's contract.

This is the point where most installations get stuck when the file has been handled halfway: if a paper from the earlier steps is missing, compensation is not activated and the surplus flows out without being discounted on the bill. The roof works, but the contract never hears about it.

What the client receives at this milestone: the contract or annex with compensation activated, whose effect then shows up, line by line, on the electricity bill.

Energy certificates and deductions: the papers worth money

The Spanish state income tax deduction for energy-efficiency improvement works allows 40% of the investment to be deducted on a maximum base of 7,500 euros, under RDL 2/2026 and for works up to 31-12-2026. It requires an energy performance certificate from before and another from after the works, registered within the deadline. Without those two certificates there is no deduction, however well the installation was built.

The Valencian Community adds its own regional deduction: 40% on a base of 8,800 euros for a main residence, 20% for a second home, and it can be carried forward over 4 tax years if a single year's tax bill does not allow it to be applied in full. It requires the entry in the self-consumption register and the IVACE certificate. If a charger for an electric car is also installed, there is a 15% deduction on a base of 4,000 euros until 31-12-2026, and in communal garages the Horizontal Property Act, in article 17.5, only requires prior notice to the owners' association to install one in an individual parking space.

The direct MOVES III grants ended on 31-12-2025, so today the playing field is the deductions. They all share the same logic: paperwork filed and registered on time, or money lost.

Who signs what and what you should keep

Throughout the journey, every signature has an owner, and it helps to be clear about it from the start:

And this is the client's folder, the one worth keeping alongside the deeds of the house:

That folder is the difference between an installation that produces and an installation that produces, offsets, deducts and can stand up to anyone's scrutiny. It is the part of the trade you cannot see from the street, and the reason behind our promise to leave it legal: the whole file, delivered and explained, not a handsome roof with an empty drawer.

• The licensed installer or engineer signs the technical report, the CIE and the legalisation documentation filed with Industry.
• The owner signs the municipal responsible declaration (even if the engineering firm prepares it), the representation authorisations for the procedures and the contract with their supplier.
• The certifying technician signs the energy performance certificates from before and after the works.

Frequently asked questions