Connecting solar panels to your fuse box: how does it work?

Solar panels deliver direct current: a constant flow in one direction, just like a battery. Your sockets and appliances run on 230-volt alternating current, and the public grid runs on alternating current too. Between the roof and your installation there is therefore an inverter that converts the direct current from the panels into usable alternating current. Without that conversion you cannot use the generated power.

The inverter does more than just convert. It monitors the voltage and frequency and ensures that what it delivers keeps neatly in step with the grid. If the grid drops out or something is wrong, the inverter switches itself off. That is a safety feature: that way no voltage can go onto the grid while people may be working on it, for example. The inverter is therefore the heart of the installation and the place where most faults arise.

From the inverter the alternating current runs to your fuse box. Preferably that happens via a dedicated circuit, with its own RCD/MCB that only protects the panels. That has two advantages. First, it is clear: you can switch the panels off separately without affecting the rest of your home, for example during maintenance on the inverter. Second, it is safer, because a fault in the solar installation does not immediately drag other circuits down with it.

An RCD/MCB combines two protections in one: it switches off on leakage current (to prevent shock hazard) and on overload or short circuit. For an installation that delivers power every day, that is the proper way to connect. In older boxes with only fuses or without an RCD, that does not simply fit in; an adaptation or replacement of the fuse box is then needed before the panels can be added.

Whether there is space for an extra circuit depends on your box. If it is already full, a module needs to be added or the box needs replacing. A certified installer assesses this beforehand, so there are no surprises.

For an average set of panels on a single-phase connection an extensive intervention is usually not needed, provided your fuse box is in order. In practice you do run up against limits. An inverter putting a lot of power on one phase can raise the voltage on that phase too far, causing the inverter to switch off and you to lose yield. With larger systems the installation is therefore sometimes spread across more phases, or a switch is made to a three-phase connection.

If you are also upgrading at the same time for an EV charger, a heat pump or a home battery, it is smart to look at everything together. Applying for a heavier mains connection goes via the grid operator and takes time. By thinking through the solar installation, the box and a possible upgrade in one go, you avoid having work done twice in quick succession. We always look ahead to what is still to come.

As soon as your panels generate more than you are consuming at that moment, the surplus flows into your meter cabinet and onto the grid. A smart meter registers this in both directions: it counts the power you draw and the power you feed back separately. In your meter readings you therefore see separate counters for draw and for feed-in. That is the basis on which your energy supplier makes up your bill.

An old, spinning Ferraris meter could run backwards on feed-in, but these are disappearing and are not suitable for modern feed-in. If you still have an old meter, the grid operator replaces it with a smart meter. The connection of the panels themselves does not change because of that: it still runs via your fuse box. The meter only determines how your generation and consumption are counted, and that is exactly what you need to know what you get back.

The panels on the roof and the cabling to the inverter are often supplied and placed by the solar panel supplier. The part after that, from the inverter to your fuse box, is genuinely electrical work on your fixed installation. Under NEN 1010 that belongs with a certified installer: the right circuit, a good RCD/MCB, cables that match the load and sound earthing.

That is not just a matter of safety, although that is the most important reason. It also matters for your guarantee and your insurance. Inverter manufacturers sometimes impose requirements on a correct installation, and if damage occurs your insurer looks at whether the work was demonstrably installed to the standard. A connection you cannot check from the outside is one you want to be right. We connect your panels with certified status, measure through the installation and hand over neatly, so it is correct and demonstrably safe.