How to Connect Your EV Charger to an Inverter for Solar Charging

Charging an EV with PV surplus power sounds amazing because it helps you use more of your own renewable energy, reduce electricity costs, and charge your car more efficiently. In theory, this sounds simple. In practice, many EV owners quickly discover that getting the charger and PV system to communicate properly is not always straightforward. How does a wallbox actually know when excess solar energy is available?  What role does an inverter play in this? Spoiler: it doesn’t always have to be part of your EV charging setup.

In this blog post, we’ll break down:

• what PV surplus charging actually means

• how a wallbox and PV system communicate

• whether the inverter must be directly connected

• the different methods for enabling solar charging

• what to look out for when planning your setup

• which wallboxes offer the most flexibility

Let’s dive in!

If you already have solar panels, using your own electricity to charge your EV is one of the most efficient ways to increase self-consumption and reduce charging costs. Instead of exporting excess solar energy to the grid for a relatively low compensation, you can use that energy directly to charge your car.

• Lower charging costs through the use of self-generated solar energy

• Greater energy independence and reduced reliance on the grid

• Lower CO₂ emissions and a reduced environmental impact

PV surplus charging means that your EV only charges when your solar system produces more electricity than your household currently needs.

For example:

• Your PV system produces 8 kW

• Your household currently consumes 3 kW

• The remaining 5 kW can be used for EV charging

The goal is to maximise self-consumption and minimise electricity imported from the grid.

One common misconception is that a wallbox can automatically “detect” solar energy on its own. In reality, the charger requires information from another device to know whether excess solar power is available.

Typically, this requires one of the following:

• An energy management system (EMS)

• Separate energy meter

• Data from the inverter or smart meter

Depending on the setup, the information can be provided:

• Directly by the inverter

• Through an external EMS

• Via smart home systems like Home Assistant

• Through dedicated hardware controllers

No, a direct inverter connection is usually not required for PV surplus charging. Some systems measure energy flows independently at the building’s grid connection using CT clamps or energy meters. In these setups, the wallbox only needs information about whether electricity is currently being imported from or exported to the grid.

As a result, smart solar charging can work with virtually any inverter — including older systems and inverters that do not support direct communication with the wallbox or EMS.

The required components depend on how the wallbox receives information about PV surplus.

There are several ways to connect your wallbox to your PV system. Generally, it comes down to four main approaches, depending on whether you want "plug-and-play" simplicity or a fully customised smart home:

• Using a proprietary EMS

• Single-manufacturer ecosystem

• Integrating via open APIs and smart home systems

• Connecting through an external EMS

The right option depends on how simple or flexible you want the setup to be.

Some wallbox manufacturers, including go-e, offer their own EMS to provide the charger with data regarding PV surplus availability. In most cases, the EMS would use its own CT clamps to measure the grid connection of the house. This is the case with the go-e Controller. In this setup, neither the inverter nor the smart power meter of the building actively communicates with the charger for surplus management.

If, in addition to charging your EV with excess solar, you want to measure and visualise your total PV production (including other power consumers in the building), you must measure the current using a sensor on one phase of your PV inverter. To achieve this, a sensor should be installed around the inverter's power supply cable*.

* Only possible for AC inverters

Some manufacturers like SolarEdge offer fully integrated ecosystems where the inverter, wallbox, smart meter, and energy management system are designed to work together within the same brand environment. In these setups, communication between devices is typically preconfigured, which can simplify installation and commissioning.

Many prefer to avoid fully integrated ecosystems because they can reduce flexibility. Expanding the system later, replacing individual components, or integrating third-party devices may be more difficult or limited compared to open systems. You may also become dependent on a single manufacturer for future upgrades and compatibility.

If you’re tech-savvy or already have a smart home hub (e.g. Home Assistant), look for a wallbox with open interfaces. For instance, our go-e Charger offers both local and cloud APIs, giving you total control over your energy management. 

To use PV surplus for charging, you need either a separate power meter installed at the grid connection of your house or an existing one connected to your PV system. In this setup, the meter provides the necessary data regarding excess solar to your smart home hub.

Many modern wallbox manufacturers also offer the option to facilitate communication regarding PV surplus through a third-party EMS. This works particularly well if the brands are integration partners. Such partnerships ensure smooth integration and significantly simplify the setup process.

A third-party EMS is not always hardware-based — it can also be a purely software solution. One example is the cooperation between go-e and Clever-PV. The Clever-PV EMS platform is designed to make automatic solar charging for electric cars simple and convenient. However, for it to work, you need to have an energy meter connected to your PV system — just like in the case of integration via an open API.

Another go-e integration partner, Embion, offers a hardware solution, such as the Embion controller. It continuously monitors solar energy excess and signals the charger once a sufficient amount of solar surplus is available. 

When planning your setup, several factors determine how efficiently and flexibly your PV charging system will work.

The most important things to consider are:

• Compatibility with your inverter and existing hardware

• Support for automatic phase switching

• Future battery storage integration

• Flexible integration options

• Energy measurement concept

• Support for dynamic electricity tariffs

Below, we’ll look at each of these aspects in more detail.

Three common solar sensor setups exist. One of the main differences between these setups is how much energy data your EMS can access and visualise. 

Sensors are installed behind the utility meter and optionally on the inverter output.

This means the system can see:

• how much electricity the house imports from the grid

• how much excess solar power is exported back to the grid

• output of the PV inverter

With this information, the EMS can control PV surplus charging correctly because it can detect when excess solar energy is available. The system can also display the exact power consumption and PV production.

This situation occurs when the sensors are installed between the PV system and the house. In this case, the EMS sensors must be installed directly on the inverter output to receive the data necessary for solar excess charging.

Now the system can measure*:

• solar production

• detailed power consumption of the entire household

* grid import/export can be calculated based on the available data

This provides a comprehensive energy overview in the app because the EMS receives both grid data and inverter production data. 

Sometimes the solar inverter is installed far away from the main electrical cabinet — for example, in a garage, basement, or separate utility room. In other cases, the inverter cables may be inside a sealed or crowded section of the installation where sensors cannot be mounted safely.

The system with an EMS like the go-e Controller in place can still perform PV surplus charging normally, because it still knows whether energy is flowing into or out of the grid. But since there is no direct inverter measurement, you can’t see the exact solar production value, or separately visualise the inverter output inside the energy flow overview. 

Some EMSs only work properly within their own ecosystem, while others can communicate with a wide range of PV systems. For instance, the go-e Controller can be used with all inverter types, regardless of brand or age. Such systems often offer greater flexibility, which is why many users prefer them.

If you plan to add a home battery later, make sure the wallbox can work together with battery storage systems and energy management platforms. For instance, the go-e Controller is able to visualise PV-AC battery production. While DC storage cannot be measured, you can easily prevent continuous discharge of the battery during your car charging by adjusting the app settings.

This allows it to switch to single-phase charging when there is not enough power available for three-phase charging. For example, if your charging current is set to 11 kW, your car will not charge using solar surplus if only 2 kW is available. A wallbox with automatic phase switching, such as the go-e Charger, will simply switch to single-phase charging and ensure that even small amounts of excess solar energy are used to charge your car battery.

When connecting a wallbox to a PV system, there are generally two approaches: proprietary integration and open integration.

This means that the wallbox is built to work directly with a specific inverter ecosystem. A good example is the SolarEdge, which connects seamlessly with SolarEdge inverters and smart meters.

Instead of being limited to one manufacturer, they support open communication standards such as HTTP API, MQTT, or Modbus TCP. The go-e Charger follows this flexible approach.

PV surplus charging is highly efficient during sunny periods. But when there is no surplus available, dynamic electricity tariffs can further reduce charging costs. Some wallboxes, like the go-e Charger, can automatically charge the vehicle during the cheapest electricity price periods while still prioritising solar charging whenever possible.