A new study by researchers from the University of South Australia (UniSA) and Deakin University, Victoria, has found that households with rooftop solar could gain more by sharing extra solar power with neighbours rather than just selling it back to the grid.
Right now, almost 40% of Australian households (around 4.1 million homes) have rooftop solar. While that’s great for clean energy, it’s also causing challenges — too much excess solar is flooding the grid, pushing down feed-in tariffs and making it harder for homeowners to get good value for their investment.
The findings, featured in the Renewable Energy journal, used real data from a 10kW solar-powered home in Geelong, Victoria. Researchers simulated how energy would be generated, used, stored, and shared under four different models over a 12-month period, including three neighbouring homes.
The research explored these options:
- Peer-to-Grid (P2G): Selling extra solar back to the grid.
- P2G with batteries: Storing energy in batteries, then exporting the rest.
- Peer-to-Peer (P2P): Selling extra energy directly to neighbours at an agreed price.
- P2P with batteries: Using stored energy first, then sharing leftover solar with neighbours.
The results were eye-opening. P2P energy sharing helped neighbours cut their grid power use by more than 30%. When paired with a 10kWh battery, the solar owner could make the highest return — nearly $5,000 over 20 years.
Dr Kevin Wang, the lead researcher from UniSA, explained why:
“Feed-in tariffs are currently less than 5 cents per kWh in Victoria, while households are paying around 28 cents to buy electricity from the grid. If neighbours buy solar directly at a middle price, both sides win – sellers earn more, and buyers pay less.”
But the study also found trade-offs. While batteries helped solar owners reduce their grid reliance, they left less surplus energy available for neighbours. Oversized batteries also reduced financial returns due to higher upfront and maintenance costs.
In one scenario, a 7.5kWh battery with P2P sharing delivered the best balance – cutting payback time to just 12 years.
Professor Chunlu Liu from Deakin University said the study highlights the need for smart choices in how we use solar:
“When batteries are used, they mostly benefit the solar owner. But when energy is shared, the whole community benefits. The real challenge is finding the right balance between self-use and sharing.”
With solar power now such a big part of Australian homes, this research suggests that neighbour-to-neighbour sharing could be the next step in making clean energy fairer, more affordable, and more beneficial for everyone.