When's the right time to invest in battery storage?

To reduce dependency on the main power grid, many owners of rooftop solar have been keeping abreast of battery storage options to assess the point at which a battery will save them enough money to cover the cost of the battery within its warranty period. Researchers at the University of South Australia (UniSA) believe that for South Australian residents, under certain conditions, this point may have arrived.

PhD candidate Vanika Sharma from UniSA’s School of Engineering recently published a paper in the journal Renewable Energy showing that an optimally sized battery can be economically beneficial in South Australia due to a combination of government subsidies, abundant sunlight, high electricity costs and relatively low feed-in tariffs.

“The crucial thing is to ensure you are getting the right size battery, and getting it at the right price,” Sharma said. “If you are, then you can now have a battery that will pay itself off in the warranty period, which is the main concern for most people.”

Although Sharma warns that there are still many cases where batteries are not yet cost-effective, she has designed a calculation that can determine whether a battery of optimal size will pay itself off based on a range of factors, allowing consumers to adjust their initial investment against projected savings.

“The optimal battery size depends on various factors, such as load and PV generation patterns, battery cost and characteristics, retail price and feed-in-tariff of grid electricity,” she explained. “But this method can assess this all efficiently, and that allows people to make the right choice for their circumstances.

“Right now, in South Australia, the break-even cost for installing a battery using this method is around $400 per kilowatt hour of battery capacity, and with the current subsidies of $500 per kilowatt hour, and retail prices on some batteries lower than $900 per kilowatt hour, you can have a cost-effective system.”

Sharma and her co-researchers, Dr Mohammed Haque and Professor Mahfuz Aziz, are also investigating whether storage alternatives, such as shared ‘community’ batteries, may present further benefits in respect to cost and system efficiency.

“The focus of the research is to minimise the waste of PV, and so we’re also looking at whether it is more effective to have batteries on every home or a central battery that could accommodate more PV, which would then also save distribution costs for providers,” Sharma said.

“The residential battery energy storage systems not only provide financial benefit to the customers but also address some of the operational issues associated with power generation, transmission and distribution,” Dr Haque added.

Prof Aziz commented, “The use of battery energy storage systems is likely to proliferate in the years to come. Future research and development should focus on how to leverage such storage to improve power system operation.”

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