Boffins looking into the Australian solar energy ecosystem say that sharing really is caring – and potentially profitable when homes with solar panels can sell their excess energy to neighbors at a preferential rate.

"Under current conditions in Victoria, the feed-in tariff is less than 5 cents per kilowatt hour, while the retail price is around 28 cents. Selling surplus PV [photovoltaic] energy directly to neighbors at a mutually agreed price in between can be more profitable for solar householders and still cheaper for buyer," lead author Dr Kevin Wang, of the University of South Australia, explained in a post-publication statement outlining the study's findings.

"Our modelling revealed that under current conditions, P2P energy sharing coupled with a 10 kWh battery could deliver the highest return – AU$4,929 (£2,370/$3,210) – for solar owners over 20 years. In contrast, all peer-to-grid scenarios resulted in negative returns over the same period due to low feed-in tariffs and high battery costs."

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The trick is that while energy suppliers are eager to charge high prices per kilowatt-hour, they're reluctant to spend the same amount – so any excess energy generated by a solar harvesting system is sold back for a fraction of what the energy companies claim it to be worth.

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A peer-to-peer distribution system between neighbors balances this out, the researchers found. Excess energy can be priced above the "feed-in tariff" rate it would fetch if sold back to the grid but below the retail price it would cost when purchased from the grid – providing additional income for the generator and discounted energy for their neighbors, cutting the energy company out of the equation entirely.

The study also found support for sizing batteries accordingly, with storage systems capable of holding over 10 kWh delivering diminishing returns owing to the higher initial purchase cost, increased maintenance costs, and a reduction in the amount of "surplus" energy generated and thus available for export from the home – whether to neighbors or the grid.

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Co-author Chunlu Liu, a professor at Deakin University, noted in a statement: "When batteries are used, they benefit the solar owner by reducing their grid reliance, but this can limit the amount of energy shared with neighbors because they are fully charged before any surplus energy is shared. The challenge is to find a balance that works for everyone."

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A key takeaway from the study, aside from the need to integrate non-battery technologies like heat pumps and thermal storage to help soak up excess generation, is that peer-to-peer sharing could be key to increasing solar uptake beyond the already-impressive 40 percent coverage of Australian homes – both by reducing the overall cost per home and also by relieving pressure on existing grid infrastructure, which is often in need of upgrade to cope with the cyclical and sometimes unpredictable supply from solar harvesting.

It does, however, fly in the face of the Australian government's recent launch of an AU$2.3 billion (£1.11 billion/$1.5 billion) [9]grant scheme to subsidize the installation of home batteries. The study found that while adding a battery to a solar harvesting setup increased self-consumption to 22 percent with a corresponding reduction in grid imports, it offered no community benefit nor provided any income for the homeowner. P2P sharing, by contrast, dropped grid consumption by 30 percent, and delivered the shortest possible payback period – 12 years from installation – when combined with a relatively small 7.5 kWh battery, while boosting self-consumption rate far higher than a battery alone.

The team's study has been published in the journal [10]Renewable Energy under open-access terms. ®

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[5] https://www.theregister.com/2025/07/28/googles_latest_renewable_energy_deal/

[6] https://www.theregister.com/2025/04/17/datacenters_feed_energy_back_unrealistic/

[7] https://www.theregister.com/2025/04/12/ai_hyperscalers_sustainability/

[8] https://www.theregister.com/2025/03/31/nuclear_no_panacea_ai/

[9] https://www.energy.gov.au/solar/financial-benefits-solar/government-rebates-and-loans-solar

[10] https://www.sciencedirect.com/science/article/pii/S0960148125011565

[11] https://whitepapers.theregister.com/