The surge in utility-scale renewable energy plants has begun, with wind and solar projects on the go around Australia, but a third force in generation is emerging in the form of corralled exports from rooftop solar-and-storage systems dotted all over the country.

German battery maker Sonnen is the latest entrant to the local peer-to-peer energy trading market with sonnenFlat, which offers participants electricity at a capped rate in return for the right to access surplus stored energy to sell into the wholesale market.

The packages vary from 7,500kWh a year for $360 ($30 a month) sold to households with 5kW of solar and 8kWh of storage, to 12,500kWh a year for $600 ($50 a month) sold to owners of systems with 10kW of solar and 12kWh of storage.

The program is open to owners of Sonnen batteries. In Australia, about 700 Sonnen batteries are fitted mostly to residential solar systems in Melbourne and Sydney, but in Germany participants in sonnenFlat include wind farms and bioenergy plants where Sonnen storage is used.

The Munich-based company launched the offer in Germany and Italy, its biggest markets, last year. It’s been attracted to Australia for the attractive combination of high solar penetration and rising wholesale electricity prices.

The maker says it needs about 2,000 participants in Australia for sonnenFlat to “have scale”, so it’s hoping for another 1,300 sales to kick the program off.

Next year, it expects a 300% increase in sales or a total 8,000 units across Australia, with sales doubling annually thereafter. If all goes well it will start manufacturing in Australia, Sonnen CEO Christoph Ostermann told EcoGeneration.

“We are taking utilities out of business,” Ostermann says.