Battery storage could be just five years away from being an economic no-brainer for some Australian solar households, according to a new report which predicts grid-connected battery storage will be economically attractive for many homes from around 2020.

The report, released on Monday by the Alternative Technology Association, says Sydney and Adelaide could be the first cities to arrive at this point – as early as 2018.

But the report is also careful to stress that the value of adding solar with storage will vary from household to household, and state to state, depending on a number of key metrics, including the household’s size, its location, its consumption patterns and the kind of tariff it is on.

“At today’s prices, most Australian households won’t be able to achieve a 10-year return on their investment – which is the typical lifetime of a well-designed and operated battery system,” said ATA policy and research manager Damian Moyse. “But by 2020, this will change for an increasing number of homes.”

To try to work out which homes, exactly, the ATA tested the value of adding batteries to a new grid-connected solar system across a range of different scenarios.

Using the ATA’s Sunulator solar-with-battery economic feasibility tool – a new technology to be launched on Tuesday in Melbourne – the study included 10 different locations, electricity consumption data for typical working couples and young families, three different grid tariff types and different sized solar systems.

The results revealed that in nine scenarios across six locations a 4kWh battery improved the net present value (NPV) for the “Young Family”. As you can see below, households from only two locations – Sydney and Adelaide– achieved this with investment in 2018. The remainder involved investment in 2020.

The graph below compares the net present value of solar only systems (4kW) in each location in 2020, as well as solar plus a 4kWh battery; and solar with a 7kWh battery, for young families on a flat tariff.

Overall, says the report, “investment in 4kW of solar PV on its own was financially attractive for larger energy homes – but not for those who have lower day-time consumption.

“Adding batteries did generally deliver savings over the ‘solar-only’ systems,” the report added – with annual savings

ranging from $132-$335 for a small battery and $187-$513 for a larger battery, dependent upon household type, location and grid tariff.

The study also found that the smaller 4kWh battery was always more attractive than the larger 7kWh one; and in no case did adding batteries significantly speed up the solar system payback time.

The following chart shows how different solar and battery system combinations work with different tariffs, and how much they save on electricity bills for a “young” Sydney family in 2016.

Of course, the report found that “smarter” battery systems – which could work with a given household’s time-of-use tariff to maximise both cheap energy storage and solar self generation – would deliver greater savings, especially if they incorporated weather forecasts.

“It remains to be seen when batteries this smart become available in Australia,” the report said.

The report also found that the economics of investing in storage would obviously be improved if households were paid to provide and share in associated benefits to the electricity grid.

The chart below analyses a scenario where an energy company co-invested $300 per kWh, off-setting the solar

household’s upfront costs.

ATA suggests energy companies could co-invest in such systems, for example, by selling batteries cheaply to households and, on critical days, could control the batteries remotely, discharging them at peak times.

Likewise, though, it remains to be seen when energy companies this smart will become available in Australia.

Until that time, or until batteries drop further in price, the ATA suggests households try cutting their bills through more effective investments, including LED lights; gap sealing, insulation and window shading; efficient appliances; ditching the gas network; and solar without batteries.

Finally, the report calls on Australian consumers to get to know their own energy profiles and to embrace energy efficiency.

“There’s a lot of hype in the community about battery storage, and while we think it is a great thing, we urge people to understand their own electricity consumption patterns and choose the most suitably sized and designed solar and battery systems,” said Moyse.

“Different consumption levels and different lifestyles require different solutions – no one size fits all.

“Having a more energy-efficient home will mean you need smaller sized batteries, which will ultimately be better for your overall energy costs and the environment,” he said.

“Batteries need to be considered in the context of an overarching, holistic energy management approach – whether that be for a household or business.”