Electrical Certification in Porto and Greater Porto (Formerly CERTIEL)

When Certification Is Actually Required — and When It Isn't

Certification is required in four specific situations: a new electricity contract on an installation that has never had one or has been disconnected for a long time; an increase in contracted power above certain limits; a significant alteration to the installation, such as a renovation that touches the consumer unit (fuse box) and the circuits; and installations in non-domestic use, which covers alojamento local holiday lets, shops and service businesses.

Outside those cases, a home that is simply being lived in on its existing contract does not need certifying just for the sake of it. We say this plainly because people regularly come to us convinced they must certify the house before they can sell it, and in most cases they don't — something worth knowing if you have been told otherwise by an agent or a friend used to the rules in another country.

Where the confusion is real is alojamento local: once a property is run as a holiday let, the installation stops counting as domestic in terms of use, and certification becomes part of what is asked for. Owners converting a family home into an AL tend to find this out late, and it is one of the most common surprises for foreign buyers who purchase with rental income in mind.

What Gets Checked, and What Fails Most Often

The check focuses on whatever protects people and whatever documents the installation. In practice that means: the presence and correct operation of the RCD (residual current device, known locally as the diferencial), continuity of the earth conductor at every point, earth resistance that is measured rather than assumed, cable cross-sections suited to the circuit breakers, proper separation of circuits and a labelled consumer unit.

The things that fail are nearly always the same: no earth at all, or an earth reading that is too high, bathroom sockets without adequate protection, and circuits protected by a breaker rated higher than the cable can carry — usually because someone swapped a breaker that kept tripping for a bigger one instead of dealing with the cause.

None of this is expensive to put right when you know about it in advance. It becomes expensive when it turns up on the day of the check, with the electricity contract waiting on the result and the building work already signed off as finished.

Our Scope: Low-Voltage Internal Installations

We install and certify the internal low-voltage installation: the consumer unit, circuits, protective devices, earthing and the technical form that goes with them. That covers the vast majority of homes, flats and small shops.

What is not within our scope is the physical connection from the grid to the property where that requires a technician qualified for medium voltage — substations and high-power supplies. In those cases we prepare and certify everything on the inside of the property and coordinate with an external technician for the part that needs that qualification.

We set this out from the start and in writing, because mixing up the two is what causes missed deadlines: some clients hire someone for the internal installation believing it includes the grid connection, and then spend weeks waiting for something nobody actually requested.

How the Process Works, Step by Step

First comes the visit and survey: we look at what is there, measure the earth and identify any non-conformities. From that you get a quote that lists the corrections that are required separately from anything optional — keeping them apart matters, so that you can decide for yourself.

Next comes carrying out the corrections and testing. Only once the tests are complete is the technical form issued and the paperwork submitted. From that point the timescale no longer depends on us, but we will tell you honestly what the usual order of magnitude is rather than promising dates we don't control.

We always hand the documents to you, the client, and not just to the electricity supplier. It is a document you will need again — for a sale, a power increase or future building work — and it is surprisingly common for nobody to have a copy. For smaller installations the document in question is the ficha eletrotécnica, which must be signed by someone properly qualified — and we explain how to confirm that in our guide on how to check an electrician is certified with DGEG.

Keep the Paperwork — You Will Need It Again

We always give the technical form and the proof of registration to the client, not only to whoever requested them. It sounds obvious, yet it isn't: we regularly meet people who certified their installation five years ago and have no copy of anything, because the document stayed with the builder or with the supplier.

You will need it again — for a sale, a power increase, future building work or when opening an alojamento local. Without it, the whole process is repeated and you pay twice for something that had already been done. If you split your time between Portugal and another country, store a digital copy somewhere you can reach from abroad.

The same goes for the consumer unit diagram: a board with every circuit labelled saves time on every future fault, and it is the difference between tracking down a problem in five minutes or fumbling in the dark by trial and error.

When is certification of an electrical installation mandatory?

For new installations, for significant alterations, and whenever a new supply contract is requested after building work. It is also often required when selling or letting a property if the installation has been altered.

What exactly is checked?

The condition and suitability of the consumer unit and its protective devices, continuity of the earth conductor, insulation of the circuits, correct operation of the RCDs and compliance of the installation with the applicable technical rules.

What happens if the installation doesn't pass?

We tell you what is missing and how much it will cost to fix, before going any further. It is usually a handful of specific points — no RCD, circuits without earth, cables that are too thin — rather than the whole installation.

How long does it take?

Checking an ordinary home is done in a single visit. The overall timescale depends on whether corrections are needed before the documentation can be issued.

Do I need to certify my house in order to sell it?

As a rule, no, if the installation stays as it is and the buyer takes over the existing contract. It becomes necessary if the buyer sets up a new contract on an installation that has been disconnected, or if building work alters the installation. If in doubt, ask before ordering anything: you may be about to pay for something you don't need.

I'm opening an alojamento local holiday let. What changes?

The framework changes: the use is no longer domestic, the installation is treated as non-domestic and certification becomes part of the licensing process. This is the situation that catches the most people out, often when bookings are already open.

My installation is old. Is it bound to fail?

Not necessarily. An old installation that was well done and has a sound earth will pass. What fails is a missing earth, an absent RCD and wrongly sized breakers. At the initial survey we tell you exactly where each of these stands and what it costs to fix, before you commit to anything.