Using Rooftop Solar to Charge Your EV at Home
Solar assisted charging allows a compatible smart EV charger to use electricity generated by your solar system when it is available. Instead of exporting all unused solar energy to the grid, the charger can direct some or all of that surplus electricity into your electric vehicle.
Some chargers refer to this function as solar charging, solar surplus charging, eco charging or solar assist mode. The exact behaviour varies by manufacturer. One charger may wait until sufficient excess solar is available, while another may combine available solar with a controlled amount of grid electricity to maintain a steadier charging rate.
Solar assisted charging can increase the amount of solar energy used within your property, potentially reducing the cost of charging an EV. It does not, however, mean the vehicle is always charged entirely from solar or that a household battery is required.
The best arrangement depends on your solar system size, household electricity consumption, driving habits, vehicle, electrical supply and when the car is normally parked at home. Make sure you contact RSEG to discuss your specific needs.
What Is Solar Assist Charging?
Solar assist charging generally means operating a smart EV charger in a mode that prioritises electricity generated by solar.
When solar panels are producing electricity, that power is first used by appliances operating within the home. If generation exceeds household demand, the remaining electricity is considered surplus solar. Without an EV charger or battery using it, this excess is normally exported to the grid, subject to any applicable export limit.
A solar compatible charger can monitor this flow and adjust EV charging according to the amount of surplus electricity available. Because electricity used directly within the property commonly has greater financial value than electricity exported under a feed in tariff, increasing solar self consumption can improve the value received from an existing solar system.
How Does Solar Assisted EV Charging Work?
A typical system may include:
Solar panels
A solar or hybrid inverter
A compatible smart EV charger
An energy meter or current monitoring device
A dedicated charging circuit
Suitable switchboard protection
An optional household battery
Monitoring or control software
The energy meter measures electricity moving between the property and the grid. The charger uses this information to determine whether the home is importing electricity or exporting unused solar.
If excess solar is available, the charger can increase its output. If clouds reduce solar production or household consumption rises, it may lower the charging rate, pause charging or supplement the available solar with grid electricity, depending on its selected mode and capabilities.
Australian Government guidance notes that smart chargers and energy management systems can automatically charge an EV when electricity is cheaper or when solar is producing excess power.
Solar Only Charging Versus Solar Assist Mode
Although product terminology differs, smart chargers commonly provide some variation of the following operating modes.
Solar only or surplus only charging
In this mode, the charger attempts to use only excess solar energy.
Charging may slow or pause when:
Solar production falls
Clouds move over the property
Air conditioning or other appliances increase household demand
The available surplus falls below the charger or vehicle’s operating threshold
This mode can maximise the proportion of solar used to charge the vehicle, but charging may be intermittent and take longer.
Solar assist charging
Solar assist mode generally combines available solar electricity with grid electricity when needed.
For example, if the charger is supplying 4 kW and the home has 2.5 kW of surplus solar available, the remaining 1.5 kW may come from the grid. The exact response depends on the charger’s configuration.
This can provide steadier charging while still reducing grid consumption.
Scheduled or off peak charging
The charger operates during selected hours, such as overnight when an eligible electricity plan offers lower rates.
This can be useful when the vehicle is not normally at home during daylight hours. Some households combine daytime solar charging with scheduled off peak charging to ensure the vehicle reaches the required charge level.
Do You Need a Home Battery?
No. A home battery is not required for solar assisted EV charging.
A compatible charger can use solar electricity directly while the panels are generating. This is often the simplest arrangement when the vehicle is parked at home during the day.
A battery can store excess solar energy for later use, including during the evening after solar production has fallen. It can therefore increase solar self consumption and reduce the amount of electricity purchased from the retailer.
However, adding a battery involves a substantial additional cost and does not automatically make EV charging more economical. The battery may also be needed for other household loads, and its maximum discharge output may limit how much power it can supply to the charger.
The financial suitability of a battery depends on:
Available excess solar
Evening household demand
EV charging requirements
Electricity tariffs
Battery capacity and output
Equipment cost
Warranty conditions
Desired blackout protection
Backup power must also be specifically designed and configured. A standard grid connected solar system normally shuts down during a blackout, and not every battery installation supplies the whole property during an outage.
Benefits of Solar Assist Charging
Greater solar self consumption
Charging an EV when solar is generating can increase the proportion of solar electricity used within the property rather than exported.
Each kilowatt hour used directly is one less kilowatt hour that needs to be purchased from the electricity retailer. The value of this saving depends on the household tariff and available feed in credit.
Potentially lower EV charging costs
Home charging can be economical, particularly when using solar or an appropriate off peak electricity tariff. Australian Government guidance specifically recommends taking advantage of daytime solar generation where practical.
Actual savings will depend on:
How much of the charge comes from solar
The grid electricity tariff
The feed in tariff being forgone
Vehicle efficiency
Charging losses
Driving distance
Solar system performance
Automated energy management
A compatible charger can adjust its output automatically rather than requiring the homeowner to monitor solar production manually.
Depending on the equipment, users may be able to:
Prioritise surplus solar
Set charging schedules
Limit grid import
Select a required departure time
Monitor charging remotely
Set a minimum vehicle charge target
Review solar and grid energy used
Management of household electrical demand
An EV charger can represent one of the largest electrical loads in a home. Smart load management can reduce charger output when other high demand appliances are operating.
Western Power advises that an electrical contractor must ensure EV charging equipment does not cause the property to exceed the capacity of its supply and connection arrangement. Where the additional load is too high, options may include upgrading the connection or installing smart EV charging equipment with grid import limiting.
What Can Limit Solar Charging Performance?
The vehicle is not at home during the day
Direct solar charging works best when the vehicle is connected while the solar system is generating.
Homeowners who commute during daylight hours may have limited opportunity to charge directly from solar. Possible alternatives include:
Charging on weekends
Using scheduled off peak grid charging
Installing a battery where financially suitable
Charging during work from home days
Using a slower rate over a longer period
Solar output continually changes
The rated size of a solar system is not the amount it will produce at every moment.
Generation varies according to:
Time of day
Season
Weather
Panel orientation
Shading
Panel temperature
Inverter capacity
Export control
System condition
A 6.6 kW solar array will not continuously produce 6.6 kW throughout the day. If a charger is set above the available surplus, the difference must come from the grid or the charger must reduce its output.
Household appliances use solar first
Solar electricity is shared across the property.
If the solar system is producing 5 kW while the home is using 3 kW for air conditioning, cooking and other appliances, only approximately 2 kW remains available before considering system losses and control tolerances.
A properly configured charger measures this changing balance rather than assuming all solar production is available for the vehicle.
The EV has its own charging limit
The charger’s advertised capacity does not guarantee that every vehicle will charge at that rate.
Actual charging power may be limited by:
The vehicle’s onboard AC charger
Single phase or three phase compatibility
Battery temperature
Battery state of charge
Vehicle charging settings
The charging cable
The property’s electrical supply
Dedicated home chargers commonly range from approximately 7 kW to 22 kW, but the electrical supply and vehicle must both support the proposed rate.
What Equipment Is Required?
A solar compatible smart charger
Not every EV charger can monitor or follow solar surplus.
Look for functions such as:
Solar surplus charging
Variable charging output
Dynamic load management
Grid import limiting
Charging schedules
Energy metering
A suitable monitoring application
Compatibility with the property’s phase arrangement
The charger does not necessarily need to be made by the same company as the solar inverter. Compatibility depends on how the charger measures energy flow and communicates with the required monitoring equipment.
At RSEG, we use the highest qualify solar technology from SolaX and Sigenergy.
An energy meter or current sensors
The charger needs to distinguish between electricity being imported from and exported to the grid.
This is commonly achieved using an energy meter or current transformers installed at an appropriate point in the electrical system. Incorrect placement or configuration may cause the charger to respond inaccurately.
A dedicated electrical circuit
A permanently installed home EV charger is connected directly to the property’s electrical supply and must be installed by a licensed electrician. The installation may require switchboard work or an upgrade to the property’s supply connection.
The electrician must consider:
Charger output
Cable route and distance
Circuit protection
Earthing
Switchboard capacity
Existing maximum demand
Single phase or three phase supply
Outdoor exposure
Vehicle location
Cable management
Future energy equipment
RSEG electricians are licensed and qualified to do all of the required work for your EV charger, including but not limited to any switchboard upgrades.
Single Phase and Three Phase Charging
Many Perth homes have a single phase electricity supply, while some properties have three phase power.
A typical 7 kW home charger can operate on a suitable single phase connection. Chargers offering approximately 11 kW or 22 kW commonly require three phase power, although the vehicle must also support three phase AC charging to benefit from the higher output.
A faster charger is not automatically the best choice. The appropriate capacity depends on daily driving, available charging time, the vehicle and the property’s electrical infrastructure.
Western Power confirms that a 7 kW single phase EV charger may be permitted on a standard single phase or three phase connection, provided the electrical contractor determines that the site remains within the applicable connection limits.
Does the Existing Solar System Need to Be Upgraded?
Not necessarily.
An existing solar system may be suitable for smart EV charging when:
It produces useful surplus energy
The monitoring equipment can be installed correctly
The switchboard has suitable capacity
A compatible charger is selected
The property’s electrical supply can support the additional load
A larger solar system may increase the amount of direct solar charging available, but expansion requires consideration of roof space, inverter capacity, existing panels, network approval and export limits.
The charger can still operate with a smaller solar system, although it may charge more slowly in solar only mode or use more grid electricity in solar assist mode.
Speak to RSEG first about your existing solar system and whether an upgrade may be right for you.
Is Solar Assist Charging the Same as Vehicle to Home?
No.
Ordinary solar assisted charging is one way: electricity flows from the solar system or grid into the EV battery.
Vehicle to home and vehicle to grid systems use bidirectional equipment that can also discharge electricity from the vehicle. Western Power distinguishes these systems from standard one way chargers and requires compatible bidirectional equipment and additional network compliance and approval.
A conventional smart EV charger cannot power the home during a blackout simply because it has a solar charging mode.
Is Solar Assist Charging Worth It?
Solar assisted charging may be particularly useful when:
The property already has solar
The EV is regularly parked at home during daylight hours
A significant amount of solar is currently exported
The homeowner wants automated load management
The electrical supply can support a dedicated charger
Charging can be scheduled flexibly
It may provide less benefit where the vehicle is rarely home during solar generation hours, the property has little excess solar or the charger’s additional smart features substantially increase the installation cost without being used.
The most appropriate solution should be based on actual electricity consumption, solar generation, driving patterns and charging requirements rather than assumptions about how the system will operate.
Planning Solar Assisted EV Charging in Perth
Before selecting a charger, gather:
The make and model of the EV
Its maximum AC charging rate
Typical daily driving distance
Normal arrival and departure times
Existing solar system size
Recent electricity bills
Solar export and consumption data
Details of any home battery
Photos of the switchboard
Information about future EVs or electrical upgrades
RSEG can assess the property’s solar system, switchboard, electrical supply and charging requirements before recommending a suitable charger and control arrangement.
Our team can assist with dedicated EV charging circuits, smart load management, solar integration, switchboard work and suitable single phase or three phase installations across Perth.
Solar Assist Charging FAQs
Can I charge an EV directly from solar panels?
Yes. A compatible charger can use electricity generated by solar while the vehicle is connected. The amount supplied by solar depends on generation and household consumption at that time.
Do I need a battery to charge an EV with solar?
No. Direct daytime solar charging does not require a household battery. A battery is only needed when you want to store excess solar for later use.
Will the EV charge when clouds reduce solar output?
That depends on the selected mode. A solar only mode may slow or pause, while solar assist mode may supplement the available solar with grid electricity.
Can an ordinary EV charger use surplus solar automatically?
Not necessarily. The charger generally requires compatible smart controls and an energy meter capable of measuring grid import and export.
Can a 6.6 kW solar system run a 7 kW EV charger?
It can contribute to the charger, but it will not necessarily supply the complete 7 kW. Actual solar production and household demand determine how much grid electricity is also required.
Is three phase power required for solar assisted charging?
No. Solar assisted charging can operate on a suitable single phase system. Three phase power may be needed for higher charging rates such as 11 kW or 22 kW.
Will my switchboard need upgrading?
Not always. An electrician must assess available capacity, protective equipment, cable requirements and the property’s maximum demand. RSEG can assess your switchboard and upgrade it if needed.
Can solar charging be scheduled?
Many smart chargers support schedules, allowing charging to occur during selected solar generation or off peak periods. Available functions vary between models.
Will the charger power my home during a blackout?
No. Standard one way EV chargers only supply energy to the vehicle. Vehicle to home operation requires a compatible EV, bidirectional charger and specifically approved system.
Can RSEG integrate an EV charger with an existing solar system?
Yes. RSEG can assess suitable existing solar installations and install a compatible smart EV charger, monitoring equipment, dedicated circuit and load management controls where required. Contact us today for a quote.
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