Charging an electric car with solar panels: frequently asked questions

Recharging an electric car thanks to the energy produced by solar panels is one of the most sustainable alternatives with which substantial savings can be made. Photovoltaic energy is considered one of the cleanest sources of energy today. As a result, more and more households are demanding photovoltaic installations to charge an electric car. In this article we answer the most frequently asked questions about charging an electric car with solar panels.

Types of photovoltaic installations for charging electric cars

Charging an electric car with solar panels is nowadays a possible and increasingly used reality. In fact, it is considered one of the most sustainable energy combinations. The way the vehicle is charged depends to a large extent on the type of photovoltaic installation. When talking about the type of installation, a distinction can be made between:

Grid-connected installation or direct self-consumption installation

This is the most common and simplest option as it only requires solar panels and an inverter. They are those installations that are carried out on sites where there is already an electricity supply.

Off-grid solar installation

Off-grid solar installation: the most expensive option in technical and economic terms, as it requires more components: solar panels, charge regulator, off-grid inverter and storage batteries, among others. This type of installation is usually carried out in locations where there is no access to the electricity grid. In this case, the only available energy source will be solar.

In the case of the first option, we would always be charging with the available surplus. Currently, the price of self-consumption surpluses is usually between 4 and 5 cents per kWh discharged.

If we focus on the latter, we see that it is the alternative that offers the greatest electricity savings. However, it is not the most efficient or practical option in most locations. Thus, to charge the electric car, we only need a photovoltaic installation that has an inverter and a battery where the energy is stored and transferred to the charger and can charge the car.

Are charging points compatible with solar panels?

Photovoltaic systems supply the charging points with energy to charge an electric vehicle. The development and technology of V2C charging points makes compatibility with solar inverters and optimisation of the installation much easier.

Trydan incorporates the best PV integration system on the market. It is the first and only charger that is compatible with all solar inverters and establishes a direct wireless connection with GoodWe, Fronius, Huawei, Ingeteam, SolarEdge, SolaX, Victron inverters as well as Shelly and Wibeee meters. This means that there is no need to install an additional current clamp, as it reads the consumption data wirelessly.

The charger is under constant development and is regularly updated. It also incorporates dynamic power control, a device that allows the power transformed by the photovoltaic inverters and the contracted grid power to be regulated while the car is being charged.

From V2C Cloud, a free multi-platform app, you can configure the power and type of charge even by time slots, and you can choose to charge the vehicle with solar surplus solar electricity generation, with the contracted electrical power or with a combination of both sources.

How much can you save by charging an electric car with solar panels?

In the context of the energy crisis and growing environmental awareness, the installation of solar panels, especially in businesses and single-family homes, is the order of the day. Although the initial investment in the installation of solar panels is usually high, the savings on electricity bills are considerable.

It is estimated that after the first 10 years, the investment is amortised and the savings can be up to 50%. In addition, there are currently multiple aid programmes and tax benefits to encourage photovoltaic self-consumption. Also, the European Next Generation Funds have a specific rebate programme. If we add to this the fuel savings generated by an electric car that can be charged with solar surpluses, the final saving far exceeds the average energy expenditure.

Is it possible to charge the car with solar panels at night or when it is cloudy?

This question is a common one. Most electric car users charge their vehicles at night, as they usually travel during the day. In this case, the most practical solution is to have a grid-connected or direct self-consumption system. In this way, the surplus stored in the batteries that has been generated during the day can be used for charging at night.

Another big question that many users have is whether it is possible to charge the electric car with solar panels when it is raining or cloudy. At this point we will start by denying that solar panels do not produce energy when the sun is not shining. This is not the case. Photovoltaic modules also work when the weather is not good. What is true is that their performance is not the same. For example, on a rainy day, they can generate between 30% and 50% of their usual production, on a day of very heavy rain their production can be reduced to 20% and on a cloudy day it can be reduced to 10%.

Is it possible to charge the electric car with solar surplus?

Yes, it will largely depend on the power required, but it is possible to charge the car with solar surplus alone. In fact, this would be the case on rainy or cloudy days or even at night. The car is powered by the stored energy.

This happens thanks to the way the solar panels work. When there is a shortage of solar power, the energy comes from discharging the battery via the solar inverter. As in the opposite case, when due to excess production, the battery cannot accept any more charge, the solar inverter increases the Hz frequency, reducing the power injected into the solar panels and avoiding overvoltage. In the same way, automatically, when there is a demand for power again, the frequency is reduced and the PV inverters increase the power.

How long does it take to charge an electric car with solar panels and how much power does it need?

Due to the climatic conditions in Spain, it is most common for a solar panel to produce between 250W and 500W of energy per hour of sunshine. If a day has 9 hours of sunshine, we will have to multiply the watts by the hours of production and divide by 1000 to obtain the production in kilowatts (kW), which is the standard measure of energy consumption. In this case, we would multiply 500W x 9 hours, which is 4500W and when converted to kW we would be talking about 4.5 kW.

Regarding the power an electric car needs to charge, most have different charging speeds ranging from 1.5 kWh to 7 kWh. In order to charge an electric vehicle with a range of 200 km, 4 kW would be needed for approximately 8 hours. So, simply by producing solar energy from one panel, we would be charging the vehicle self-sufficiently. Obviously, there are more energy demands in a household, therefore, it is recommended to install grid-connected photovoltaic or direct self-consumption installation to be able to compensate for the peaks in energy demand.

How many solar panels do I need to charge my electric car?

It will depend on many factors and the energy needs of the installation site. The most common way to charge an electric car regularly is to install an average of 4 to 5 solar panels. As we have seen above, this is already more than 4 kW and needs to supply the rest of the household’s energy needs.

What is the price of a photovoltaic installation?

The current average price of a photovoltaic installation is between €0.8 and €1.4 per kWh. In other words, in order to assess individually whether this is a profitable alternative, the average annual consumption per kWh should be studied. For a house that consumes 6,000 kWh per year, the price for the installation of solar panels could be between 4,000 and 7,000 euros. However, the price will always depend on the type of installation and the components required.

We will continue to update and answer all your questions about photovoltaic energy and its link with electric car charging points. At V2C we support renewable and sustainable energy sources by building #TomorrowToday.

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