Solar Panels in Porto and Greater Porto — Electrical Work and Connection

What the Electrical Side of a Solar Installation Involves

A home photovoltaic system has three parts, and only one of them is the 'panels'. There are the modules on the roof, there is the inverter that converts the direct current the panels produce into usable alternating current, and there is the connection to the house's consumer unit — which is the point where the system stops being a piece of equipment and becomes part of the electrical installation.

That third part is where we work: a dedicated circuit from the inverter to the consumer unit, protection on both the DC and AC sides, isolation switching, earthing of the system and integration with the protective devices already in place. It is also the part most often done badly when an installation is sold as a sealed package and fitted in a hurry.

Earthing the modules and the mounting frame is not a bureaucratic formality: a rooftop system is the highest point of the house, and without proper equipotential bonding and a suitable surge protection device it becomes the favourite way in for a voltage surge.

Self-Consumption, Surplus and What Really Pays Off

The calculation that decides everything is simple and almost never done: how much of the energy produced you can use at the very moment it is produced. This is called the self-consumption rate, and it is what determines your real savings — not the installed capacity.

In a house that stands empty during the day, with everyone out at work, a large system generates power at hours when nobody is using it, and the surplus is worth far less than the energy you save. In that scenario, more panels do not improve the numbers; what does is shifting consumption — the washing machine, the water heater, charging the car — into the sunny hours.

That is why sizing a system by the roof area available is the most expensive mistake in the sector. The right size comes from the household's actual consumption profile, and you get that by looking at the bills and the way you live, not at the roof.

Batteries: When They Make Sense and When They Don't

A battery stores the daytime surplus so you can use it in the evening. It makes sense when your self-consumption rate is low because of your routine and you cannot shift your usage, or when there are frequent power cuts and you want independence — something more common on the outskirts of Greater Porto than in the city itself.

It makes less sense when your consumption already happens during the day, because the battery ends up doing a job the house was already doing for free. In that case the money goes further spent on something else in the installation.

What you need to know beforehand is that a battery changes the protective devices and the way the whole system operates, especially if it is set up to run in island mode when the grid goes down. It is not an accessory you can bolt on without touching anything else.

Our Scope, Stated Plainly

We carry out the internal electrical work and its certification: inverter connection, consumer unit, protective devices, earthing and the installation's documentation. We work both on systems we supply and on systems you have already bought from another supplier — that exact request comes to us quite often.

We do not make the physical connection to the grid in cases that require a technician qualified for medium voltage. For self-consumption installations that export surplus to the grid and fall into that category, we coordinate with an external technician, and we tell you so before you commit to anything.

We also do the part that usually gets forgotten: preparing the house for solar before it exists. If you are renovating — as many people who buy an older house in the Porto area do — leaving conduit and a cable route from the roof to the consumer unit costs little now and saves a full round of building work two years down the line.

Is it worth installing solar panels in Greater Porto?

It pays off mainly for households that use power during the day: people working from home, homes with a heat pump or an electric car charging in daylight. Porto gets fewer hours of sunshine than the south of Portugal, but a system properly sized for self-consumption still delivers a return.

Do you handle the grid connection for selling surplus power?

The internal electrical work and the connection to the consumer unit are down to us. Registering the self-consumption production unit and exporting surplus to the grid involve a separate process and a technician qualified for that purpose. We tell you from the outset what we handle and what needs that additional step.

Do I need batteries?

They are not compulsory and they don't always pay off. Without batteries, you use the power at the moment it is produced. Batteries make sense if you use most of your electricity at night or want independence during power cuts, but they add considerably to the cost of the installation.

Do you maintain existing installations?

Yes: checking connections and protective devices, the inverter, production monitoring and diagnosing drops in output.

I bought the panels elsewhere. Will you do just the electrical installation?

Yes, and it is a common request. We ask to see the technical data sheets for the inverter and the modules first, to confirm the protective devices and cable sizes. We don't install equipment we cannot verify technically.

How many panels do I need?

That comes from the household's real consumption and daily routine, not from the size of the roof. With a year of electricity bills and a chat about your habits, a system can be sized quite precisely. Installing more than you can use is the most common way of spending money you never get back.

What if the roof has old tiles or contains asbestos?

The mounting structure changes, and in some cases installing is not advisable. On a roof made of old fibre cement you don't drill or fix anything until that issue, which is not an electrical one, has been dealt with. We tell you at the visit rather than leaving the problem for installation day.