Solar power and electric car charging

Solar and electric cars get on for a very specific reason: the system produces when the car tends to be parked. Making use of that is not automatic; the charger has to know how. Here we explain how the two fit together and what to ask for so that it works.

How a solar system works

The panels turn sunlight into direct current through the photoelectric effect. The silicon modules fitted on homes today have conversion efficiencies of around 15% to 22%.

That direct current is no use as it is: the house runs on alternating current. The inverter takes care of that, and it also monitors the system and lets you see output in real time. It is the component that most shapes how the whole thing behaves, and it is also where the integration with charging is decided.

The surplus, which is what this is about

At midday a domestic system usually produces more than the house uses. That surplus is exported to the grid and credited on the bill at a low price. Using it inside the house is worth considerably more than selling it.

That is where the charging point comes in. With a measuring sensor in the main consumer unit, the charger sees in real time how much energy is spare and adjusts its power to use exactly that. The car absorbs the surplus instead of exporting it. When a cloud passes, it drops; when it clears, it rises.

Which charger you need

Not all of them allow it, and it is the question to ask before buying anything. In our charger range charging from photovoltaic surplus comes as standard on the Woltio Pro, which also includes the measuring sensor in the price, and on the V2C Trydan. The Policharger NW has it as an option and the Orbis Viaris Uni Plus is ready to integrate with photovoltaic systems.

On installed price, the Woltio Pro page is the most sensible starting point when the panels are already there. If the installation has to integrate with an external management platform, the V2C Trydan page.

Dynamic load balancing, which is not the same thing

It is worth not confusing two functions that usually come together. Solar charging decides how much spare energy is sent to the car. Dynamic load balancing decides how much power the charger can use without tripping the house.

The second is the one that saves you having to increase your contracted power. The charger measures what the home is using and steps aside when the oven and the hob are on. It is what makes it possible to charge every night without touching your electricity contract.

Sun by day, off-peak tariff by night

If the car is away all day, direct solar charging adds little. In that case what brings the bill down is scheduling charging for the off-peak hours of your tariff, which costs nothing and is set up from the charger itself.

The sensible approach is usually to combine the two: solar surplus when the car is at home and a time-of-use tariff when it is not. Adding a battery makes sense once that has been squeezed and the pattern of use justifies it.

What it costs

A domestic solar system of around 5 kW sits, as a rough guide, somewhere between €6,000 and €9,000, with panels, inverter, mounting and labour. It varies a great deal with the roof, the orientation and the existing consumer unit, so the figure is there to give you an idea, not to quote from.

The charging point is separate and there we do give a fixed price: between €1,450 and €1,950 for most installations, with the unit, materials, protective devices, labour, commissioning and registration. Model by model, in the charger range.

In a residents' association

Solar panels on a shared roof are collective self-consumption and need the association's agreement and an allocation of shares. A charging point in a privately owned space does not: notifying it is enough, because the Horizontal Property Act does not require approval. They are two separate procedures and they can be done separately. We set it out in installations in residents' associations.

Grants

For the charging side there are two grants still available: the 15% income tax deduction, with a maximum base of €4,000 and a deadline of 31 December 2026, and the Energy Saving Certificate, €600, if you have bought an electric car and have scrapped or sold a combustion car that had been yours for more than a year. The conditions are in the article on grants currently available for installing a charging point ES. Self-consumption schemes depend on each regional government and change from one call for applications to the next.

If you want to see the numbers for your own case, in our calculators you can compare the running cost of an electric car against a combustion one and estimate the charging time for your model.