PV surplus charging guide for your Tesla

1. What is PV surplus charging?
2. What do you need for PV surplus charging?
3. Which wallbox can do dynamic PV surplus charging?
4. Can you operate a wall box with solar power?
5. How big does a photovoltaic system have to be for a wall box?
6. Where can I get advice on PV surplus charging?

What is PV surplus charging?

More and more people are using the power of the sun to generate electricity independently and are usually installing a photovoltaic system on their own roof. Photovoltaic means the direct conversion of light energy from sunlight into electrical energy using solar cells.

If you produce more electricity with your photovoltaic system than you need yourself, there will be a PV surplus. You can either feed this into the public power grid or use it to charge your Tesla. If you charge your e-car with this electricity, this is referred to as PV surplus charging.

There are 3 forms of PV surplus charging:

Manual excess loading

If you have a PV system but no automatic energy management, it is still possible to charge your Tesla manually with excess PV. You activate or deactivate the charging process via your smartphone, on the Tesla or on the wall box depending on the energy supply or regulate the charging current strength.

For this type of PV surplus charging, you need a network-enabled inverter or smart meter and a controllable wall box.

The advantage of such a manual solution is the relatively low investment costs, since you do not need any additional components and pay for their installation. This is also possible with any PV system. A disadvantage, however, is the associated higher effort and manual monitoring.

Automatic surplus charging

If you want to ensure that your e-car is only charged with your own PV power, you need an automatic controller or an energy management system.

Such an energy management system continuously measures the currently fed-in PV power and therefore knows how much power is still available in the PV system and how much can be loaded into your Tesla using one of the suitable wall boxes for PV excess charging.

A value is defined at which the inverter transmits the activation command to the wallbox. The wallbox then starts the charging process with the preset charging power. The charging power is not dynamically adapted to the available current. There is only start and stop.

The advantage of automatic PV excess charging is a significantly more efficient use of the self-produced PV electricity. However, there are additional investment costs for a smart wall box and for the corresponding energy management system.

Dynamic PV Surplus Charging

Dynamic PV surplus charging goes one step further than automatic surplus charging. An installed smart meter recognizes the current flow of electricity on the meter and controls the charging process of the wall box depending on the current surplus.

The charging power is dynamically adjusted to the surplus. This means that fluctuations in the PV power can be used and passed directly to the wall box. So it is the best way to charge with your own solar power.

A smart meter or measuring transducer with a compatible wall box or a smart wall box that specializes in dynamic excess charging is required for dynamic surplus charging.

What do you need for PV surplus charging?

The components you need for PV surplus charging depend on which solution you choose, ie whether you prefer manual, automatic or dynamic surplus charging.

Irrespective of this, you must of course have a corresponding photovoltaic system, which usually consists of 2 components, the solar modules on the roof and an inverter that feeds the electricity into the house or the power grid.

If sufficient electricity is produced by such PV systems, this first flows into domestic consumption, the rest or surpluses are traditionally fed into the public power grid. However, the price you get for excess electricity is very low. This makes it all the more worthwhile to charge your electric car with this excess PV.

A word on the subject of wallboxes: In principle, every wallbox can be operated with electricity from a photovoltaic system. However, if you want to ensure that if there is a PV surplus, the solar power is actually fed into your electric car and not into the grid, a suitable wall box is a good investment.

Which wallbox can handle dynamic PV surplus charging?

In order to use dynamic surplus charging, it is necessary to use a correspondingly compatible wall box. In the meantime, the selection in this regard is relatively large, because the topic is simply becoming more and more important in times of rising electricity prices.

The most well-known wall boxes that can dynamically charge excess PV are the Myenergi Zappi and the “My smart wall box” Black Edition by EnergieSOLUTION . Both also have integrated load management and a type 2 connector. This means that they work for every electric car and all Tesla models, even if there are several charging stations.

Myenergi Zappi

To the shop

"My smart wallbox" Black Edition by EnergieSOLUTION

To the shop

Can you operate a wall box with solar power?

In general, you can simply operate your wall box with solar power, but in this case your photovoltaic system must be of an appropriate size.

If you want to charge your Tesla with solar power without any worries, you need to add a power storage unit to such PV systems. Such a system temporarily stores excess solar power produced.

Without electricity storage, it is necessary to charge your Tesla Model 3 or Model Y exactly when your PV system generates more electricity than is currently needed in the household. If you have such an electricity storage device, you can charge your vehicle at any time of the day.

How big does a photovoltaic system have to be for a wallbox?

In order to be able to use your solar power to charge your Tesla, it must be sufficiently large. The electrical output of such systems is given in "kilowatt peak" [kWp]. With this value it is possible to determine a comparable performance of the solar cells under standardized test conditions. Due to a wide range of environmental influences, these maximum values ​​(hence “peak”) are usually not reached, since the performance also depends on the actual solar radiation and the orientation of the panels.

Under optimal conditions, a slightly larger solar power system with 12 kWp could generate an annual energy volume of 12,000 kWh. In Germany, Switzerland and Austria, due to the prevailing weather conditions, an installed capacity of 1 kWp can be assumed to have reached a value of approx. 0.8 kW, which means that our example produces an annual electricity yield of approx. 9,600 kWh .

Normal photovoltaic systems on a family home are usually designed for a system size between 7 and 15 kWp. If you want to charge your Tesla Model Y or 3 with solar power, it is therefore necessary to plan an additional 15 m² roof area and approx. 2.5 kWp photovoltaics, whereby these are estimated figures. For the exact dimensioning of your photovoltaic system, it is best to consult a specialist company, as it also depends on when you charge, how many kilometers you cover a day, etc.

If you are the owner of a very small solar power system, you must note that many electric cars can only start and maintain a charging process if there is an available power of approx. 1.4 kW single-phase (4.1 kW three-phase) and more. Such low currents are very inefficient and about 20% is lost to thermal energy. The aim should therefore be to be able to supply the Tesla with 11kW charging power.

Where can I get advice on PV surplus charging?

If you would like advice on the subject of PV surplus charging, the company energieloesung in Germany offers a whole team of experts who will advise you free of charge and also help you to choose the right wallbox. You can find the contact details here .