PV surplus charging

Climate friendliness and sustainability: These two goals are often in the foreground when setting up a solar system. However, in order to achieve the set climate goals of the Federal Government, the decision to install a PV system will no longer be left to the owners or companies. With the solar obligation, which the Federal Government is expected to decide in the near future, there is no alternative. It is therefore all the more important that the systems are used as profitably and economically as possible. In other words, the higher the own consumption, the more worthwhile the investment.

One way to significantly increase self-consumption is to use the self-generated electricity for PV surplus charging of electric vehicles by means of a corresponding wallbox and/or a load management system. In this article you will learn what PV surplus charging is, how it works, which variants there are and which advantages and disadvantages result from this.

In PV surplus charging – also known as solar charging or solar surplus charging – the solar system and the existing charging station are coupled together. As soon as the production exceeds the self-consumption, the surplus electricity is used to charge one or more electric vehicles. The use of self-generated electricity in the building area is of great advantage, but especially in the case of surplus – i.e. the amount of electricity that is generated but not consumed in the building – potential can be raised. Probably the most obvious option is to feed the surplus into the public grid. However, while the purchase of a kilowatt hour currently costs around 37 cents, the feed-in fee is considerably lower. After the feed-in fee has been reduced by a further one percent as of February 1, 2024, it is only 8.11 cents, a trend that continues to fall. In order to operate a photovoltaic system economically today, the highest possible self-consumption is crucial. The higher this is, the more profitable the PV system works. In order to significantly increase self-consumption, the PV surplus charging of electric vehicles is therefore a good idea.

An electric car and a PV system are, of course, basic requirements for PV surplus charging. In order to control the flow of electricity, an inverter, a wall box and/or a dynamic load management system are also needed. The purchase of a battery storage can also be useful, especially if the electric vehicle is only connected to the charging station at night and no solar power can be generated. In this case, the PV surplus can be temporarily stored in the battery for night-time charging.

Is PV surplus charging really worthwhile for everyone? Prerequisite is a solar system that produces a significant surplus on a recurring basis. For example, the own demand of a family of four is an average of 4,000 kWh per year. An electric vehicle that covers 10,000 kilometers needs an additional 2,000 kWh to charge. For example, a system with 10 kWP, i.e. a production of 8,000 kWh per year for two vehicles, is sufficient. A system with less than 7 kWP output, on the other hand, is out of the question because the surplus generated is too small.

The concept of PV surplus charging is therefore particularly rewarding for larger PV systems such as those found in apartment buildings, in municipalities or in factory or commercial buildings. This creates a lot of PV surplus, so that entire fleets can be supplied accordingly.

Dynamic charging requires an investment in an intelligent wall box or a load management system. However, the latter pays off. A dynamic load management system measures in real time on the main power meter, whether energy is currently being drawn from the public power grid or fed into it. This is done by means of a two-way meter at the transfer point of the building connection. As soon as a negative value is measured, there is a surplus that can be used to charge electric vehicles. Alternatively, the building consumption can be measured and deducted from the current generating capacity. The remaining power is provided for the charging. However, a dynamic load management system does not only process the information from the meter to register a feed-in and automatically start the PV surplus charging. Instead, the integration of inverters also allows battery storage to be integrated and controlled to enable targeted and sustainable charging.

Thus, the advantages of surplus PV charging are fully realized, especially:

• Eco-friendly charging
• Cost savings of up to 70 percent
• Independence of electricity suppliers and price fluctuations
• Sustainability
• Profitability of the solar system
• Higher grid stability due to low load on the grid during charging

But there are also disadvantages to PV surplus charging? Here is only the one-time investment. But this can quickly pay off with a leading load management. Unlike a wallbox, load management offers far-reaching possibilities. These include, for example, different charging demos or settings for prioritizing charging processes. Thus, the advantages clearly outweigh.