A new generation of chargers will allow electric vehicle batteries to return solar power to our homes, providing free, zero emissions electricity - day and night.

New bi-directional electric vehicle chargers will soon arrive in Australia, offering a way for solar homes to extract more value from existing rooftop installations.

The chargers allow electric vehicles to send power back into homes and the electricity grid, replicating many of the functions currently delivered by home batteries like Tesla’s Powerwall.

Just like a home battery, this will allow EVs to capture excess power from solar panels during the day, then use that energy to run electrical devices at night or during periods of heavy cloud cover.

Household energy storage is becoming more valuable, with falling feed-in tariffs meaning there is less benefit from exporting excess solar generation. Capturing more power on site means that households are able to use more of their solar power and reduce the need to buy energy from the grid.

Big batteries

Electric vehicle batteries are typically much larger than a household system, with an entry level Tesla Model 3 able to store almost five times as much energy as the company’s Powerwall 2 home battery.

This leaves enough capacity for most households to use a car for daily errands and some vehicle-to-home power supply, given the average Australian vehicle travels just 36 kilometers per day.

The new chargers will cost approximately $10,000 when they become available, but that cost is predicted to fall by more than half within a few years.

Initially the chargers will be able to return power from EVs into homes (vehicle-to-home), but as regulations are updated there will be more opportunities to participate in schemes that share energy with the broader grid (vehicle-to-grid) during times when electricity supplies are stretched.

The first chargers are due to arrive in April, with most of the initial delivery committed to major projects that will trial ways of using electric vehicle batteries to strengthen the electricity grid.

These trials will use EVs in ‘virtual power plants’, charging from renewable energy when supplies are plentiful and prices low, then aggregating large numbers of EVs to return energy to the grid when demand rises.

If successful, these projects will become more common and offer a way for households to generate revenue from their electric vehicle.

Compatibility 

Not all EVs can support bi-directional energy flows, but a new standard will see more compatible models on the market soon.

Currently, only the Nissan Leaf and Mitsubishi plug-in hybrid offer vehicle-to-home capability in Australia, but Volkswagen has promised to offer the technology in all models from this year.

Other models offer vehicle-to-load options, allowing the car battery to run directly power tools, cooking devices and other electric appliances.

This functionality means that as EVs approach parity with fossil fuel powered cars, there will be more opportunities to slash fuel and electricity bills, helping to reframe the way we use our cars beyond just a means of transport.