Win-win-win: How solar panels can also charge your EV

Australia has vast solar resource – leading the world and still growing fast. Harnessing solar PV to charge electric vehicles presents a triple win for the energy grid, the economy and the collective wallet.

That’s because EVs can make use of renewable power that may otherwise be wasted, lowering bills as well as carbon emissions by reducing the need to burn coal and gas.

Millions of Australian households already have rooftop solar – and within a few years, millions of Australians will also drive EVs. Combining the two presents a major opportunity. The rise of solar-powered homes in Australia

Australia’s solar power generation has increased more than tenfold in the last decade. As of November 2024, Australia had topped 4 million rooftop solar installations, totalling 25GW of capacity – more than the capacity of the entire coal-fired power station fleet.

The reasons for sustained growth are obvious: Australia has lots of sunshine and every kilowatt-hour of solar energy used is one less kilowatt-hour households have to pay for. Plus, households with solar PV can earn feed-in tariffs – essentially getting paid for selling power back to the grid. That means dollars saved – or earned – on the power bill every day.

According to the Clean Energy Council, Australian households have now collectively saved up to $6 billion annually off their energy bills, which equates to an average of $1,500 a year per installation and up to $150 billion in collective savings over 25 years.

The challenge now is to harness more of that clean power.

How solar panels generate electricity

Solar panels convert sunlight into electricity through a process called the photovoltaic effect – hence the term ‘solar PV’. When sunlight hits the solar cells, it excites electrons, creating an electric current. This direct current (DC) electricity is then converted to alternating current (AC) by an inverter, making it suitable for home use and EV charging – and there lies the opportunity.

Integrating solar panels with EV charging

Combining solar panels and electric vehicles maximises the benefits of both technologies. Here's how they can work together:

1. Direct charging: During daylight hours, excess solar energy can be used to charge EVs directly, reducing reliance on grid electricity.

2. Battery storage: Home battery systems can store excess solar energy for EV charging during night time or cloudy days, or for powering the home overnight if the EV doesn’t need a charge, further reducing bills and CO2 emissions. Plus battery storage systems can enable households to sell stored solar power back to the grid when export prices are highest – and thereby reduce overall energy system costs and emissions.

3. Smart charging systems: Advanced EV chargers can be programmed to prioritise solar power when available, optimising energy use and cost savings. These can be integrated with smart home energy management systems to get the best overall efficiency and balance between home and car.

Home EV charging systems

Home EV charging options range from basic ‘level 1’ portable chargers that plug in to standard sockets and charge slowly – they can take a day or two to fully charge an EV.

More advanced ‘level 2’ wall mounted units offer faster charging – and can fully charge in EV in around 6 hours.

Smart chargers use energy meters to monitor solar generation and adjust the charging rate to match available solar power. This allows homeowners to maximise the use of their solar energy for EV charging, potentially charging their vehicles using 100 per cent renewable energy during sunny periods.

Smart chargers can also be programmed to make best use of time of use tariffs – so if there is no solar power available, they can still charge at the cheapest periods.

Environmental and financial benefits

The integration of solar power and EVs offers significant environmental and financial advantages:

1. Reduced carbon footprint: By using solar energy to charge EVs, users can significantly lower their carbon emissions compared to using grid electricity or fossil fuels.

2. Energy Independence: Solar-powered EV charging reduces dependence on the grid and fossil fuels, increasing energy security.

3. Cost savings: While the initial investment in solar panels and EV charging infrastructure can be substantial, the long-term savings on electricity and fuel costs are significant. Typical payback periods for rooftop solar systems in Australia are around three to four years.

4. Grid stability: EVs can act as mobile energy storage units, potentially helping to balance the grid by storing excess solar energy during peak generation times and feeding it back when needed. As the number of EVs on the road increases, vehicles acting as a fleet of batteries to help smooth grid demand peaks and troughs will become increasingly valuable – potentially offering EV drivers a four-figure annual income stream. Hence Australia working to enable vehicle-to-home and vehicle-to-grid a reality.

Challenges and considerations

While charging EVs using solar PV offers cost and environmental upside, there are some trade-offs:

1. Initial costs: While they will pay back in the medium term, the upfront investment for solar panels, inverters, battery storage systems, and EV charging equipment can be substantial.

2. Efficiency factors: The efficiency of solar panels can vary based on location, weather conditions, and sunlight exposure.

3. Grid Integration: As solar penetration increases, there's a need for continued investment in grid infrastructure and smart technologies to manage the variability of solar generation effectively. These come at a cost, which has to be recouped through energy bills – which may see standing charges rise as households consume fewer kilowatts and export to a grid originally designed as a one-way system.

The future of solar-powered EVs in Australia

The future of solar-powered EVs in Australia is promising – and despite ongoing growth in solar PV, there is plenty of open road ahead:

1. Untapped potential: Australia is currently using less than 5 per cent of its potential capacity for rooftop solar. The combined annual output from rooftop solar could theoretically reach 245 TWh, more than the current annual grid consumption.

2. Technological advancements: Ongoing research and development in solar PV technology continue to improve solar cell efficiency and reduce costs. ARENA has set an ambitious target to improve solar efficiency to 30 per cent and reduce the cost of solar modules to 30 cents a watt by 2030 – less than half of current costs.

3. Government initiatives: Programs like the Federal Government's $1 billion Solar Sunshot manufacturing support program are expected to boost future progress by leveraging world-leading research and innovation.

4. Growing EV market: As EV adoption increases in Australia, the demand for solar-powered charging solutions will grow, fuelling innovation and investment.

5. Growing grid services market: As renewable power displaces fossil-fuel power and transport is increasingly electrified, higher power demand peaks will necessitate higher incentives for those households and EV drivers that can help balance the grid. That means special tariffs and payments, bringing down cost and carbon emissions not just for those households and EV drivers – but all bill payers.

Everyone wins

Given about a third of Australian households now have solar PV, harnessing that renewable energy to charge their vehicles represents a huge opportunity to reduce energy bills and carbon footprints while accelerating the renewable energy transition.

While electric vehicles produce lower lifecycle emissions than petrol or diesel cars even when charged via Australia’s power grid, charging EVs via solar – which produces minimal emissions during operation – can save tonnes of CO2 per year.

Which means a win for the wallet, the Australian economy, and the power grid.