Charging an EV at home with solar panels sounds straightforward: generate electricity on the roof, send it to the car, and use less electricity from the grid.
In practice, home energy systems are not always built in the same way.
One Rheidon customer in Italy uses two independent sources of electricity at home. One is the normal electricity grid. The other is a solar PV system with battery storage that can operate as a separate source.
Rather than combining everything into one tightly integrated energy ecosystem, the customer uses a physical transfer switch to choose which source supplies the relevant circuit. The EV charging system then works downstream of that choice.
Choosing where the electricity comes from and managing how much electricity is available for EV charging are two different functions.
How to charge an EV at home with solar panels
At its simplest, a solar PV system produces electricity during daylight hours. If the home is using electricity at the same time, some of that solar generation can be consumed directly.
An EV connected at home can become one of those electrical loads.
Adding battery storage changes the timing. Instead of having to use all available solar electricity when it is generated, some of it can be stored and used later.
The UK Energy Saving Trust explains the same basic principle: solar batteries store electricity generated during the day so that it can be used when it is needed later. Depending on the system, stored or excess solar electricity can also contribute to EV charging.
That does not mean every solar-powered EV charging system works in the same way.
The route between the solar panels and the car depends on the wider electrical architecture of the home.
Some homes use an integrated system in which the solar inverter, battery, energy-management system and EV charger exchange data and coordinate their behaviour.
Others keep some of these functions separate.
The customer setup in this case belongs to the second group.
What changes when battery storage is added?
Without battery storage, using solar electricity for EV charging usually depends heavily on timing.
If the car is at home and charging while the panels are producing enough electricity, some of that generation can be consumed directly. If the car arrives later, much of the solar production may already have passed.
Battery storage creates another option.
Energy generated earlier can be stored and made available later according to the way the household energy system has been designed.
That can make solar generation more useful for a car that is not necessarily plugged in during peak production hours.
But a battery does not decide, by itself, how the wallbox should behave.
The wider home system still has to determine:
- which source of electricity is active;
- how that electricity is distributed;
- which household loads are supplied;
- and how much power can be allocated to EV charging.
This distinction becomes particularly important in homes with more than one independent source of electricity.
How does solar and battery storage affect the cost of charging an EV at home?
For UK drivers asking how much does it cost to charge an electric car, there is no single figure that applies to every home.
The result depends on several factors, including:
- the vehicle’s energy consumption;
- the household electricity tariff;
- when the vehicle is charged;
- how much energy comes from the grid;
- and how much comes from solar generation or stored energy.
Home charging and public charging can already have very different cost structures. HMRC’s advisory electric rates for fully electric company cars, for example, distinguish between home and public charging. These are mileage reimbursement reference rates rather than universal consumer charging prices, but they illustrate an important point: where the electricity comes from matters economically as well as technically.
Solar generation can reduce the amount of electricity a household needs to buy from the grid. Battery storage can also change when self-generated electricity is available for use.
That does not make solar EV charging “free”. Solar panels, battery storage and the wider electrical system all involve their own costs, and the actual economics depend on the household.
The more useful question is therefore not simply, “What does one full charge cost?” It is also:
How much of the energy used to charge the car needs to be purchased from the grid?
A real setup with two independent power sources
In this customer’s home in Italy, the energy architecture is relatively unusual but easy to understand once the functions are separated.
There are two power sources.
The first is the electricity grid.
The second is a solar PV system with battery storage, operating as an independent source.
The customer specifically chose to install a physical transfer switch. That switch determines which source supplies the relevant household circuit.
This is a real customer installation in Italy. The diagram explains the functional relationship between power-source selection and EV load management; it is not an installation wiring diagram. Residential supply arrangements, earthing requirements and EV chargepoint installation rules differ by country. In the UK, the installation must be designed for the property’s actual electrical supply and applicable UK wiring and safety requirements.
The important point is the order.
By the time electricity reaches the charging system, the choice between grid electricity and the solar-storage system has already been made.
The wallbox does not need to make that decision again.
Why AC500 does not need direct communication with the inverter in this setup
Solar EV charging is often presented as an integrated communication problem.
The inverter knows how much solar electricity is being generated. An energy-management system monitors what the home is consuming. The wallbox can then adjust charging according to that information.
That is one valid architecture.
It is not the only possible architecture.
In this customer’s installation, the source-selection decision happens upstream of the charging equipment.
AC500 does not have to decide:
Is this electricity coming from the grid or from the solar inverter?
The household switching system has already determined which source is active.
The WB500 then charges the vehicle using the supply available on the circuit, while AC500 performs its load-management role.
In this specific configuration, direct communication between AC500 and the solar inverter is therefore not required for AC500 to manage the charging load.
That statement is deliberately specific to this installation.
It does not mean that communication with an inverter is unnecessary in every solar EV charging system.
In an integrated home energy ecosystem, communication between the inverter, battery, EMS and charger may be central to functions such as automatic solar-surplus charging or coordinated energy management.
Different architectures solve different problems.
Power source selection and load management are different functions
The easiest way to understand this customer setup is to separate two questions.
1. Where does the electricity come from?
This is power source selection.
In the customer’s home, the possible sources are:
- grid electricity;
- solar PV plus battery storage.
The customer uses a physical switching device to make that selection.
2. How much power should go to the EV?
This is load management.
The purpose is not to identify the origin of the electricity. It is to manage the electrical load available for charging.
That is the role performed by AC500 in this setup.
Charging current limits can also be adjusted through the app in supported configurations.
This gives us the most important technical distinction in the case:
Power source selection is not the same as charging load management.
The two can interact, but they do not have to be controlled by the same device.
Integrated solar system or independent energy architecture?
There is no single architecture that fits every home.
A tightly integrated solar ecosystem can make sense where the homeowner wants solar production, storage, household consumption and EV charging to be automatically coordinated.
A more modular setup can make sense where parts of the home energy system already exist and perform separate functions.
| Aspect | Integrated solar system | Customer setup |
|---|---|---|
| Power source selection | May be coordinated through the inverter, EMS or other system components | The source is selected upstream using a physical transfer switch |
| Grid and solar-storage system | May operate within one coordinated energy ecosystem | Remain two independent power sources |
| Inverter communication | Depends on the architecture and the functions required | AC500 does not require direct inverter communication in this configuration |
| Role of the wallbox | Charges the vehicle as part of the wider energy-management system | Charges the vehicle using whichever supply is active |
| Load management | May be integrated with the wider energy-management logic | Handled separately from power source selection |
Neither approach is automatically better.
An integrated system can provide centralised automation.
A modular system can allow existing parts of a home energy setup to continue doing the jobs they were designed to do.
What matters is whether the charging solution fits the electrical architecture that is actually present.
Where WB500 and AC500 fit into the system
In this installation, the roles of the two Rheidon products are deliberately limited and clear.
The WB500 is the residential EV charging point.
The AC500 manages the charging load.
AC500 is not being used as:
- the solar inverter;
- the battery-management system;
- the physical transfer switch;
- or a replacement for the home’s existing solar-energy controls.
Its role begins after the active power source has already been selected.
That distinction matters because it avoids treating the EV charger as though it must control every part of the home energy system.
Sometimes the better question is not:
Can my charger control my inverter?
but:
What does my charging system actually need to control?
In this case, source selection and charging load management are separate jobs.
What this case shows for homes with solar and battery storage
When adding EV charging to a home with solar panels, homeowners often begin with product compatibility:
Which wallbox works with my inverter?
That is a reasonable question, particularly for an integrated solar ecosystem.
But it is not the only useful starting point.
Another question is:
How is energy already organised in my home?
Homes can be configured in many ways:
- grid supply only;
- grid-connected solar;
- solar with battery storage;
- solar and storage coordinated through a single EMS;
- or separate energy sources with their own switching and control logic.
The charging equipment has to work within that real architecture.
This customer chose to keep grid electricity and the solar-storage system as two independent sources. A physical switch selects the source upstream, while the charging system manages the EV downstream.
It is not a universal template for solar EV charging.
It is a real example of a broader principle:
The charging system does not always need to redesign the way the whole home manages energy.
In brief
- Solar panels can supply household loads, battery storage and EV charging depending on the home energy architecture.
- Battery storage can make self-generated electricity available later.
- In this Italian customer setup, grid power and solar-plus-storage remain two independent sources.
- The active source is selected upstream through a physical transfer switch.
- WB500 and AC500 operate downstream, with AC500 handling the charging load rather than selecting the energy source.
FAQ
Can I charge an EV at home with solar panels?
Yes. Solar PV can provide electricity that contributes to EV charging at home. How much solar energy reaches the vehicle depends on the solar system, household demand, whether battery storage is present and the wider electrical configuration.
Can I use a home battery to charge an EV?
In a system designed to support it, stored electricity can contribute to household loads, including EV charging. The actual behaviour depends on the design and control logic of the home energy system.
How much does it cost to charge an electric car at home?
There is no universal figure. The cost depends on the vehicle, electricity tariff, charging time and how much electricity is purchased from the grid. In a home with solar panels and battery storage, part of the charging energy may instead come from self-generated electricity, reducing the amount purchased from the grid.
Does a wallbox need to communicate with the solar inverter?
Not in every architecture. In this customer setup, the active power source is selected before electricity reaches the wallbox. AC500 therefore does not need direct inverter communication to perform its load-management role in this configuration. Other systems may use direct communication as part of their energy-management logic.
What is the difference between solar energy management and EV load management?
Energy management determines how electricity is generated, stored, selected and distributed around the home. EV load management determines how much electrical capacity can be allocated to charging. The two functions can work together, but they are not the same thing.
Can a home switch between grid electricity and stored solar energy?
This particular customer installation can. A dedicated physical transfer switch is used to select between the two independent sources. That does not mean the same arrangement is suitable for every home; the appropriate configuration depends on the electrical system and the equipment installed.
EV charging should fit the home that already exists
Solar panels, battery storage, the grid and an EV charger can form one integrated ecosystem.
But they do not always have to.
In this customer setup, the energy source is selected upstream. WB500 and AC500 then handle EV charging and the associated load management downstream.
That separation is what makes the case useful.
Not every home manages energy in the same way. EV charging should fit the real energy architecture of the home. Any similar configuration should therefore be assessed against the property’s actual electrical system and local installation requirements, with the installation carried out or verified by a suitably qualified professional. If you are considering a similar home charging and load-management setup, contact support@rheidon.com to discuss a configuration tailored to your existing home energy system.
