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Around 36% of homes in the SWIS (South West Interconnected System) have rooftop solar PV systems, so it makes sense for electric vehicle (EV) drivers in WA to make the most of that renewable energy.

For EV owners, charging electric cars at home with solar panels could be possible depending on factors including your solar PV system size, your consumption habits, whether you have a battery, charging schedule and choice of EV.

Rooftop solar PV systems are distributed energy resources (DER) – and so are EVs. The WA State Government has what’s known as the DER Roadmap, which includes plans to optimise renewable energy sources, including from all that famous WA sunshine, to help power WA homes, businesses and electric vehicles.


Making the most of rooftop solar

Peak solar power generation happens during the sunniest part of the day, usually between 10am and 3pm. During this time, many households with rooftop solar PV systems generate more electricity than those households use at the time, and the excess electricity not being used by each household is exported  to the electricity grid.

Rooftop solar PV system owners should explore how to make the most of their solar investment to use up that excess solar power rather than exporting it to the electricity grid. In some cases, this could include installing a home battery system to store solar generated electricity for later use, including to charge an EV. Using stored solar generated energy is one of the possible ways to use renewable energy to charge an EV.


EVs in Australia

The methods you could use to charge your EV will depend on which type of EV you have. Currently, the most common types of EVs in Australia are:

  • Hybrid Electric Vehicles or HEVs

    HEVs are petrol or diesel cars with a small electric battery. These cars can drive using the battery alone when travelling at low speeds, but when a HEV needs to go faster, the petrol or diesel engine will kick in. These cars do not plug in to recharge their battery.

  • Plug-in Hybrid Electric Vehicle or PHEV

    Plug-in hybrid electric vehicles (PHEVs) use batteries to power an electric motor and petrol or diesel to power an internal combustion engine. PHEV owners can charge the vehicle battery through external charging equipment – such as a charging cable or a wall box EV charger. Some PHEV can also charge their battery while being driven through  a concept known as regenerative braking. 

  • Battery Electric Vehicles or BEVs

    Battery Electric Vehicles or BEVs run only using electricity with no petrol or diesel required. This means that they don't produce direct carbon emissions from burning petrol or diesel while driving. As with PHEVs, these electric cars can be charged using an external source such as plugging in through a charging cable, a wall box EV charger or electric vehicle charging station.

If you have a PHEV or BEV you could explore how you may be able to use electricity generated by solar panels if you have a rooftop solar PV system installed at your home or business to help charge your EV.  


Electric vehicle charging stations and other ways to charge

All plug-in EVs currently available in Australia have a lithium-ion battery – but because plugs and connectors differ between vehicles, not all types of charge points or charging stations can be used by all plug-in EVs.

As a general rule, there are three “charging levels” to charge a plug-in EV.

Level 1: AC Charging via an Electric Socket

This charging method can be comparatively easier for some people, but it’s also the slowest way to charge an EV. It involves plugging your EV mobile charge cable into a normal electrical socket or outlet to use the applied current (AC) power from your home to charge the EV. This is the slowest charging method, known as ‘trickle charging’, and can take up to 14 hours to fully charge an EV battery from empty.  This option could include renewable energy as part of the charging mix if you have a rooftop solar PV system and charge during the day when the sun is shining. If you have an average size rooftop solar PV system, it’s very likely that you would still need to draw some power from the electricity grid even if your rooftop solar PV system was generating at full capacity. 

Level 2: AC Fast Charging via a Wall Charger

With a wall box EV charger, you may be able to use the AC power from your home to charge your EV at a faster rate than a standard electric socket. To charge your EV with solar generated electricity as part of the charging mix, you could charge while your rooftop solar PV system is generating electricity during the day. It’s likely that you would also need to draw some power from the grid during this time to complete your charge. 

Your EV converts this AC power into direct current (DC) power that becomes stored energy in your EV battery. You may be able to have an EV charger installed by a registered electrician at your home, or you might find wall box EV chargers at restaurants, hotels or shopping centres. Fully charging your EV with a wall charger is generally much faster than charging via a standard electric socket and can take up to eight hours. 

Level 3: DC Fast Charging

Fast charging requires a high-voltage DC charger which is the type of charger typically found at  public electric vehicle charging stations. By supplying power directly to the battery, many compatible EVs can fully charge in just twenty to thirty minutes. This kind of EV charger are used throughout the WA EV Network and could include renewable energy as part of the charging mix depending on a number of factors including the time of day you use the charging station.

Learn more about charging your electric vehicle, in our ultimate EV charging guide.


Charging electric cars at home with solar panels

Whether you plan to install a wall box EV charger or you’re happy to just plug your EV into a normal electrical socket, if you have a rooftop solar PV system, you have options to potentially use solar generated electricity as part of the charging mix to charge your EV. In summary:

  • The inverter in your rooftop solar PV system is designed to make sure your home uses the solar power that your rooftop solar PV system generates first. 
  • You’ll only draw electricity from the grid when your own solar power supply is not enough to meet your electricity demand, such as at night, on cloudy days or when you have a lot of appliances such as your pool pump, dishwasher and washing machine running at once. Charging your EV during the day could be a great way to maximise the solar power your rooftop solar PV system generates. 
  • Instead of exporting excess energy to the electricity grid for a small feed-in tariff, you could use that solar power effectively to charge your EV.
  • When you’re home and able to charge your EV during the day, the solar power from your rooftop solar PV system may be able to partially or fully charge your EV. 

If you’re like many Australians who do most of their driving during the day or have your car at work during the day, you may have other options to help manage your charging costs. You could be able to access a time of use (TOU) plan such as the EV Add On plan.*

For example, you could install an EV charger at home and schedule in when you would like your EV battery to charge. With a smart charger, you could leave your EV plugged in to charge either during the middle of the day to make the most of the solar power generated by your rooftop solar PV system, or overnight to make the most of the Synergy EV Add On plan.* 

Using even a small amount of solar power from your rooftop solar PV system instead of electricity grid-supplied power to charge your EV could help you to reduce your potential electricity costs. For example, you may be able to work from home to charge your EV when your rooftop solar PV system is generating, or plan your weekend driving and charging habits to maximise use of your solar power.


Your EV could be a stored energy solution in the future

If you’re part of any EV driver communities, you might have seen discussions around using an EV for stored energy in the same way as a home battery, using a bidirectional charger. This ability is currently being trialled overseas in places like the United States, United Kingdom and Europe. 

Here’s how it works:

  • An EV with bi-directional charging capability – also known as vehicle-to-grid (V2G) or vehicle-to-home (V2H) charging – can take power from the grid to charge the EV battery, AND supply power back to the grid, or to a home, using energy from the EV battery. 
  • Owners of bidirectional charging-capable EVs might be able to tap into that stored energy to supply power to their home or export it to the electricity grid, meaning that an EV could act in the same way as a home battery storage system.

It’s worth noting that only those EVs with a bidirectional charger – known as a CHAdeMO charge port – could potentially do this. In Australia, at the moment only a small number of EVs have this, including the Nissan Leaf EV and the Mitsubishi Outlander PHEV – however these aren’t generally able to be used for stored energy in this way in Australia presently.

There is currently a trial backed by the Australian Renewable Energy Agency (ARENA) happening in Canberra to test the technology, so we might see this kind of storage ability being available in Australia in the future. 


Driving your solar power further

Your EV is similar to other devices in your home: making the most of the potential to reduce the cost of your EV depends on your consumption and usage habits and other factors. By making informed choices in how you use electricity to take advantage of renewable energy options, you could help to reduce your carbon footprint with your EV.

If you’d like to further explore how to maximise use of your EV and possibly reduce your electricity costs, see if you could benefit by switching to a time of use electricity plan, such as the Synergy EV Add On plan.*



*Eligibility criteria and terms and conditions apply to the Synergy EV Add On plan.