Extending Your Electrical Installation in Porto and Greater Porto

The Mistake You Pay For: New Appliances on an Old Circuit

The most common extension of an installation in Greater Porto is the kitchen. The gas cooker goes, an induction hob comes in, and the hob gets connected to whatever circuit was already there, because “it's the same socket”. It isn't: an induction hob draws between 3.5 and 7 kW, several times what the old appliance used.

The consequences don't show up straight away, and that is exactly what makes it dangerous. The cable heats up inside the wall for months, the insulation breaks down, and the symptom eventually appears as a smell, a discoloured socket or a breaker that starts tripping for no obvious reason.

The same applies to air conditioning, heat pumps, water heaters and car charging. All of them need a dedicated circuit running from the consumer unit, with its own cable size and protection. Done properly, it is half a day's work; done too late, it means an opened-up wall.

Enclosing a Balcony, Converting an Outbuilding or Adding an Office: What Changes

Enclosing a balcony or converting a room turns an outdoor space into a lived-in one, and the requirements change with it: a single outdoor socket is no longer enough, and you now need lighting, a proper number of sockets and, if there is heating or cooling, a dedicated circuit.

With outbuildings and converted garages another issue comes up: the supply comes from the main house, often through an undersized cable that was laid for one light and one socket. If the outbuilding is going to become an office or living accommodation, it is usually worth fitting a sub-distribution board with its own protection rather than stretching the existing circuit.

For remote working there is one more detail people only regret afterwards: running data cabling while the walls are open. At that stage it costs almost nothing and puts an end to the problem of Wi-Fi that never quite reaches.

When an Extension Means Working on the Consumer Unit

Not every extension needs a new consumer unit. It does when there is no free space for the new breakers, when the board still has fuses or has no RCD, or when the combined load of the appliances needs more power than the installation can safely carry.

In those cases it is better to decide once: replacing the consumer unit during the extension costs a fraction of doing it as a separate job six months later, because the labour and the power cut are already happening. See our consumer unit page.

Then there is the formal side: if the extension is significant, the installation will need fresh certification. We raise this during the visit and include it in the quote, because it is one of the costs that most often appears as a surprise at the end of a job. Where the extension is significant, such as new circuits fed from a replaced consumer unit or a change in how the property is used, the installation may have to be declared again; this is where knowing when the ficha eletrotécnica (the electrical installation form) is mandatory comes in. The form is in Portuguese and we can deal with it for you.

Pools, Outdoor Areas and Bathrooms: Where the Rules Get Stricter

Some parts of the home have tighter requirements, and those are exactly the places where people improvise the most. Bathrooms have defined zones around the bath and shower where only equipment with the appropriate protection is allowed; a socket added next to the basin for convenience may well sit inside one of those zones.

Outdoor areas, gardens and swimming pools add water and constant exposure to the weather: sealed weatherproof boxes and fittings, dedicated RCD protection, and cable rated for burial, which is not the same cable used indoors. A garden extension lead plugged into an indoor socket is one of the most dangerous set-ups we come across, and one of the most common.

This is also where “just adding one socket” stops being cheap: it is not the socket itself that costs money, it is the circuit with the right protection. When an extension involves these areas, we say so during the visit and explain why, rather than quoting a price that doesn't cover what the installation actually requires.

Can I add sockets without touching the consumer unit?

Sometimes, yes, if the existing circuit has spare capacity and the cable size allows it. But adding load to a circuit that is already at its limit is what causes tripping and overheating, so we check beforehand, not afterwards.

I'm installing an induction hob. Does it need its own circuit?

Yes. An induction hob needs a dedicated circuit with its own protection and a suitable cable size. Connecting it to the kitchen socket circuit is one of the most common causes of repeated tripping.

Can the installation be extended without breaking into walls?

Often, yes, by using existing conduit or surface trunking. We look at the cable route during the visit and tell you honestly what needs chasing into the wall and what doesn't.

Do you extend installations to garages, outbuildings and outdoor areas?

Yes: outdoor lighting, garage sockets, outbuildings, gates, irrigation systems and barbecue areas. In those cases we use materials rated for outdoor use and fit separate RCD protection.

I'm getting an induction hob. Do I really need a new circuit?

In practice, almost always. The hob needs a dedicated circuit with the right cable size and its own protection, and the circuit in an older kitchen rarely meets that. We check during the visit: if a suitable circuit happens to be there already, we tell you and you save the work.

How long does it take to add a circuit?

If there is a route for the cable and space in the consumer unit, half a day to a day. What varies is the route: through trunking or existing conduit it is quick; chasing into a stone wall is another matter. We can tell during the visit.

I'm renovating in stages. When should I call the electrician?

Before plastering and before the floors are laid, because that is the only time running cable and conduit is cheap. Calling after the building work is finished is the number one reason quotes end up doubling.

I want extra sockets in a bedroom. Is that a big job?

It depends entirely on the cable route. If there is usable conduit or a skirting trunking system, it is a matter of hours. If it means chasing into a stone wall and then making good and repainting, most of the cost is no longer electrical. We see it during the visit and give you both options.

Do I need permission from the condomínio for electrical work?

The condomínio is the building's owners' association. Inside your own flat, you don't need its permission. You do when the work touches shared parts of the building, such as the rising main, the landing distribution boxes, the facade or the roof, or when it involves increasing the supply to your flat. We tell you during the visit which case applies, so you don't find out halfway through. Bear in mind that building administrators and owners' meetings in Portugal generally work in Portuguese, so it helps to know early whether their approval is needed.