Guide to Charging an Electric Car with Photovoltaics

An electric car can become a home's largest new energy load—or the most efficient use of your solar generation. This guide to charging an electric car with photovoltaics explains what you need to measure before choosing a wallbox, inverter, battery, or photovoltaic-system capacity. Proper design does not begin with the charger's kW rating. It begins with the distance you travel, the hours the vehicle is parked at home, and the actual output of your installation.

How much energy does an electric car actually need?

An electric vehicle typically consumes between 15 and 22 kWh per 100 kilometres, depending on the model, driving style, load, speed, and use of climate control. For 40 kilometres of daily travel, the energy required is often 6 to 9 kWh. Over a year, this becomes a significant but entirely manageable additional load.

The critical factor is when the vehicle charges. If it is at home or at the business mainly during midday hours, it can directly use photovoltaic generation. If it returns every evening and charges only at night, the day's production must either be settled through the current net billing scheme or partly stored in a battery. These two cases require different technical and financial approaches.

Photovoltaics and EV charging: the correct design approach

A photovoltaic system does not “charge the car directly” in the way it is often presented. Energy is managed through the building's electrical installation, the inverter, the meter, and—where present—the energy-storage system. The goal is to increase self-consumption: to use as much of the solar generation as possible at the time it is produced.

To achieve this effectively, the wallbox must be able to adjust its charging power dynamically. When surplus solar energy is available, the charger increases its output. When clouds pass or major household loads switch on, it reduces the charging rate. This is known as photovoltaic-surplus charging and relies on an energy meter or current sensors at the supply connection point.

Without dynamic management, a high-power wallbox may draw electricity from the grid when only smaller or fluctuating amounts of solar production are available. This is not necessarily wrong—especially when fast charging is the priority—but it does not maximise the financial benefit of self-consumption.

The wallbox rating is not the required photovoltaic capacity

An 11 kW three-phase wallbox does not mean that you need an 11 kWp photovoltaic system. The charger rating is the maximum power it can deliver to the vehicle, not a permanent load. It can charge at a lower power—for example, 1.4 kW, 3.7 kW, or 5 kW—depending on available generation and system settings.

The photovoltaic system should be selected for the complete energy profile: the home, heat pump, air conditioning, professional equipment, and electric car. An installation designed before the purchase of an EV may need to be expanded, but this is not always the case. We first assess consumption and production data, rather than simply adding up appliance nameplate ratings.

Single-phase or three-phase wallbox?

The answer depends on the property's electrical supply and the vehicle's onboard charger. With a single-phase supply, charging is often limited to 3.7 or 7.4 kW, provided that the installation supports it and the correct provisions have been made. With a three-phase supply, an 11 kW wallbox is often a balanced choice for a home or business, provided that the vehicle supports three-phase AC charging.

Higher power is not always better. For someone who drives only a few kilometres and leaves the car parked all night or all day, lower-power charging may be sufficient and better suited to using solar generation. In contrast, a business with vehicles that must return to the road quickly has different requirements and may need several charging points with load management.

The technical study also checks the available supply capacity, main distribution board, protective devices, earthing, voltage drop along the cable route, and simultaneous operation of other loads. A wallbox should not be treated as simply another socket on the wall.

Do you need a battery to charge the car?

A LiFePO4 battery is not essential for a successful photovoltaic EV-charging installation. It can, however, be particularly useful when the car charges after sunset, when grid outages are frequent, or when greater energy autonomy is required.

There is an important trade-off. A battery has a cost and finite capacity. An electric car may require 10, 20, or more kWh in a single charging session, so a 5 or 10 kWh home battery is not usually designed to cover every overnight charge in full. Its role is to cover the building's essential needs, use solar energy outside production hours, and—where designed to do so—support critical loads during an outage.

Load prioritisation is crucial in hybrid systems. The system can be configured to cover household needs first, charge the battery next, and then start or increase vehicle charging. In another application—for example, a business—the vehicle may be assigned a higher priority. There is no single setting that suits everyone.

What dynamic load management provides

Dynamic load management protects the electrical supply from overload. It measures in real time how much power the property is using and adjusts EV charging so that the supply limits or configured safety thresholds are not exceeded.

This is especially valuable in homes with electric cooking, a water heater, heat pump, or air conditioning, and in businesses with variable loads. If several appliances switch on at the same time, the charger temporarily reduces its output rather than causing an issue at the main breaker. In installations with two or more vehicles, load balancing distributes the available power among chargers according to the priorities you define.

How correct sizing is carried out

A reliable study is based on real data. It requires electricity bills or consumption measurements, the vehicle's annual and daily mileage, parking times, the capacity and type of electrical supply, and the available area and orientation for the photovoltaic array.

Seasonality requires particular attention. In summer, photovoltaic generation may comfortably cover a significant share of daytime charging. In winter, production is lower and vehicle energy consumption often increases because of heating and weather conditions. The decision should not be based only on a sunny day in July.

For homes and businesses in Greece, the applicable settlement framework and grid-connection terms must also be checked case by case. The technical solution must be compatible with the inverter, meter, charger, and requirements of the electrical installation—not simply a collection of devices from different manufacturers.

Choosing equipment: compatibility matters more than the name

Premium equipment from manufacturers such as Victron Energy, GoodWe, Fronius, SolarEdge, or Deye can provide reliable monitoring, advanced energy control, and integration capabilities. Nevertheless, the correct choice is not determined by brand alone. It depends on inverter compatibility with the storage system, communication with the wallbox, the ability to measure surplus production, and installation quality.

Dedicated protection, correct wiring, suitable earthing, and installation by a licensed electrician are required. Charging from a standard household socket may serve occasional needs, but it is not the correct solution for daily, extended charging. A dedicated wallbox provides controlled power, greater safety, scheduling, and better use of photovoltaic generation.

Hellenic Energy approaches every such project as one integrated energy system: generation, consumption, storage, and charging are assessed together so that the investment performs in practice, not only in a theoretical calculation.

The right next step is to record for one week when the car is at your property and how many kilometres you travel. This simple information gives a free technical study the foundation needed to turn charging from an unpredictable expense into controlled solar energy.