Charging an electric car at home - The how-to!

You are already a proud owner of a photovoltaic system and are now thinking about buying an electric car? You already own an electric car and are considering to buy a photovoltaic system? Our how-to is perfect reading for both scenarios. We will demonstrate how you can combine an electric car and photovoltaic system to achieve a completely new level of self-sufficiency.

Good for the environment & your wallet: Use excess solar power to charge an electric car at home

The 'eMobility' in Germany is in vogue. More and more electric cars can be seen on German roads. Figures published by the Federal Motor Transport Authority confirm this trend. In the first half of 2019, new registrations of electric cars increased by around 80 per cent compared to the same period in 2018. The Federal Government's target is to have more than 1 million electric cars on the roads in Germany by 2020.  However, many environmentalists criticise the CO2 balance of electric cars where they feel is a backlog, especially in battery production and the electricity generation. If you use the excess solar power to charge your electric car at home rather than feed it into the grid for little money, you would both use it in a more environmentally friendly way and save money. Protecting the environment can be so easy if you have a solar-powered charging station at home for your electric car.

The basics of a photovoltaic system

It is helpful to understand the general function of a photovoltaic system to realise the benefits of charging an electric car at home. Usually, the system generates more electricity than is required in the household. If the sun shines during the day, for example, no lighting and subsequently less electricity are needed. However, the photovoltaic system is producing electricity in top form. Therefore, this electricity must first of all be utilised differently. Modern systems connect to a domestic power storage unit, where electricity is stored until it can be consumed in the house. Nevertheless, and especially in the summer months, the generated electricity will always be greater than the available storage capacity in the house.

What happens to excess electricity? It is fed into the nationwide grid and compensated with around 11 cents per kilowatt-hour. This represents a bad deal for the photovoltaic system's owner as he has to pay around 25 to 30 cents when they draw the electricity from the grid. Conclusion: The owner should consume as much electricity as possible from his photovoltaic system. If you have a charging station for electric cars at home, your electric car can contribute towards this target.

Charging an electric car with photovoltaic electricity

Does it make sense at all to have a charging station for electric cars at home? As a preference, you should aim to charge your electric car at home while the sun is shining and avoid charging via a diversion to your power storage unit. The electricity generated by your photovoltaic system can be used directly to charge the electric car as long as the created excess electricity is sufficient and does not impact on the power supply of your household which would always be a priority. With a modern domestic charging station for electric cars, you can set the ratio of solar and grid power used for the charge and the desired charging time window.

Why do you need a Wallbox charger?

A Wallbox establishes an appropriate plug connection from the charger to the electric car. It provides an optimum of electrical protection for all system components. Visual displays on the Wallbox indicate whether the electric car can be charged.  Intelligent Wallbox chargers can also communicate with photovoltaic systems and reduce the use of grid power during the charging process to a minimum. For this, it is irrelevant whether the photovoltaic system is connected to a power storage unit or not. Make sure your home charge station is suitable for your vehicle. Not all of the electric cars support fast charging with higher power output. Inappropriate use of the Wallbox can lead to expensive damage to your electric car.

Where should you charge your electric car?

There are two options to charge your electric car. Similar to conventional petrol stations a growing network of public charging points exists.   However, getting electricity from these charging points is very expensive. Depending on the provider, you will be charged for up to two euros per kilowatt-hour. It is cheaper if you use a home charging station for electric cars. If you charge the vehicle from the socket, it will usually cost you between 25 and 30 cents per kilowatt-hour - a clear cost advantage compared to the public charging stations. If you mainly utilise the excess electricity generated by your photovoltaic system charging will become even cheaper, in some cases almost free of charge. It does pay off to install a home charging station for electric cars.

How much does it cost to charge an electric car?

The cost of charging your e-car depends on the location of the charging station and the capacity of the vehicle battery. Public charging points are the most expensive. It helps, just like with conventional petrol stations, to compare prices and identify the cheapest provider. It becomes cheaper if you have a home charging station for electric cars and use the electricity from your home socket. In this case, charging for 100 kilometres costs about four to five euros. However, the cheapest option is to mainly use the electricity generated by your in-house photovoltaic system to charge the e-car. A distance of 100 kilometres will then only cost you two to three euros.

Is it worthwhile to charge your e-car with your PV electricity?

We did already mention at the beginning of this blog post that it is especially beneficial to use as much power as possible from your photovoltaic system yourself and not to feed it to the public grid.  With an in-house power storage system, you can already use 50 to 60 per cent of the electricity yourself. If you operate a home charging station for electric cars with self-generated electricity you can increase the ratio of self-consumption to up to 70 per cent. Charging your e-car at home will not only drastically reduce the cost per kilometre but also increase your self-consumption of excess solar energy from your photovoltaic system, resulting in further substantial savings. 

When does an electric car become CO2 neutral? 

The CO2 balance of electric cars is a vexatious topic. Supporters of e-cars claim a CO2-neutral operation of the vehicles. Studies presented by its opponents suggest that e-cars emit even more CO2 than petrol or even diesel vehicles.
It is a fact that e-cars do not emit any CO2 at all in road traffic. They are significantly more environmentally friendly and healthy than their counterparts with internal combustion engines. They help to reduce CO2 emissions and fine dust pollution in inner cities.

However, for a full carbon footprint evaluation of e-cars emissions during the manufacturing process and during battery charging also need to be taken into account. The mode of power generation plays an important role. If you charge your electric car at home and use electricity generated by coal-fired or even nuclear power plants, you will not be able to use your electric car in an environmentally friendly manner.

If you use verifiable green electricity or a photovoltaic system for charging your carbon footprint will improve and you can at least ensure that the operation of your e-car is carbon neutral. And that's already a good starting platform. The longer you drive the vehicle, the more you can offset its manufacturing CO2 emissions. According to a Volkswagen study, the eGolf overtakes its diesel counterpart from a mileage of 125,000 kilometres onwards. However, as a prerequisite, your home charging station needs to be powered by green electricity or in the best-case scenario by electricity from your photovoltaic system.

Conclusion: Charge your e-car at home? It's worth it!

The operation of an electric car is under normal circumstances already much cheaper than running a car with a classic internal combustion engine.  However, the cost advantage depends on the mode of charging. If you only use a Wallbox in your garage to charge your e-car and do without public charging stations, you will save a lot of money. It will be even cheaper if you use electricity generated by your photovoltaic system for your home charging station. The intelligent load management of the power storage unit provides excess electricity for the e-car as soon as the storage batteries are charged.   Conversely, it will also ensure that the electricity is fed into the storage batteries when the e-car is completely charged. Charging your e-car at home is not only cheaper but also very environmentally friendly. Nothing is stopping a CO2-neutral operation of the electric car.