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Efficient and sustainable: Charging electric cars with PV surplus


The Fronius Wattpilot charging solution shows just how cost-effective and sustainable charging an electric car can be, particularly if you use PV surplus from your own photovoltaic system. The Fronius Wattpilot is one of the few charging stations on the market that can switch between single-phase and three-phase surplus charging automatically. The result? The electric car receives the maximum amount of PV energy. Charging a vehicle does not get cheaper than that. 

The right charging solution for PV surplus charging

If you already have your own photovoltaic system or are planning on getting one in the future, it makes sense from an ecological and economical perspective to use self-generated solar energy to charge your electric car too. This makes it possible to reduce charging costs and the photovoltaic system pays for itself faster thanks to the higher level of self-consumption

When choosing the right charging station, it is important in this case to consider the function of PV surplus charging. Thanks to dynamic PV surplus charging, such as the kind enabled by the Fronius Wattpilot, surplus PV current can be put to optimal use and feeding into the grid reduced to a minimum

The Wattpilot is one of the few products on the market that can switch between single-phase and three-phase surplus charging automatically. The advantage of this is that all the excess energy of 1.38 to 22 kW is used. The Wattpilot follows the sun’s curve perfectly and utilizes the full output of the photovoltaic system. Even the smallest amounts of excess energy are used to charge the electric car. Charging is completed in 1-ampere steps and 1/3-phase switchover takes place fully automatically. 


How dynamic PV surplus charging works

A starting power level and 3-phase power level can be defined for dynamic PV surplus charging. 

The starting power level specifies the surplus amount that the photovoltaic system needs to reach before the Wattpilot begins charging the car. 

The 3-phase power level is the surplus value that needs to be reached by the photovoltaic system to switch from1-phase to 3-phase charging. The figure shows the example of a starting power level of 1.38 kW and a 3-phase power level of 4.14 kW. If the PV surplus is between 1.38 and 4.14 kW, the Wattpilot regulates the charging power in 230 Watt steps. If the PV surplus exceeds 4.14 kW, the Wattpilot will switch from 1-phase charging to 3-phase charging in 690 Watt steps. 

A compatible inverter in the same network as the Fronius Wattpilot and a Fronius Smart Meter are required to charge an electric car with PV surplus. 

The open interfaces of the Fronius inverters enable direct communication with the Fronius Wattpilot. Communication takes place via Solar API using WLAN and ensures optimal coordination between the inverter, Smart Meter and charging solution. 


Charging prioritizations during PV surplus charging

The prioritization of loads and setting of limit values forms the basis for the distribution of the available PV energy. Let us assume that there is a Fronius Wattpilot, Ohmpilot, and battery in the photovoltaic system; prioritization will decide when the electric vehicle begins to charge. 

For example, the settings can be adjusted so that first the battery is sufficiently charged or the water must be heated before the excess PV power is used to charge the electric car. Another option is that the electric vehicle is charged first before the battery and Ohmpilot. The settings can be adjusted according to the needs of the respective photovoltaic system and customer. 


Two intelligent charging modes 

When charging an electric car, there are two different charging modes to choose from: Eco Mode and Next Trip Mode. Eco Mode is the ideal charging mode for PV system owners. Here, PV surplus is prioritized for charging the electric car. If there is also a variable energy tariff, the low-cost green power tariff from the grid will be used for the remainder of charging. 

Next Trip Mode is used to refuel with energy for a specific route. Electric car drivers enter the exact distance and time of the next journey via the Solar.wattpilot app. Targeted charging is then completed to the required energy level right up to the defined, desired distance. 


Charging is even easier with your own app

The Solar.wattpilot app makes the charging solution easier to commission and operate. Several functions, including charging modes, can be adjusted via the app. Charging with PV surplus and limit values in combination with other loads, such as a battery or the Ohmpilot, can also be activated and adjusted in the app under the “Cost optimization” function. 

Get the Solar.wattpilot app in just a few steps:

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