Australia could get an extra 2 gigawatts of electricity – the boost Prime Minister Malcolm Turnbull wants from an expanded Snowy Mountains hydroelectricity scheme – through batteries and connecting a quarter of the houses that already have solar panels.

The same increase in power could come from equipping 400,000 solar homes with a battery such as a 5-kilowatt Tesla Powerwall 2, a Tesla spokesman said on Thursday.

It would be a quicker process than expanding the hydro dam, which could take at least four years.

Just connect to grid: A Tesla Powerwall - or other such battery - could boost Australia's energy supply faster than a Snowy Hydro expansion. Supplied

"If you were to take one quarter of the Australian households with solar and apply a Powerwall, allowing half of that Powerwall to be aggregated into the grid, you'd have the same amount of power as would come from the boost of an expanded Snowy Mountains hydro at a fraction of the cost and a time frame of one to two years," the spokesman said.

The notion of using batteries to stabilise power grids got a boost this month when Tesla founder Elon Musk offered to build a $100 million, 100MWh battery farm in 100 days. But it's not a major leap. A CSIRO report for industry association Energy Networks last year predicted that by 2027 electricity customers would be generating 29 gigawatts of rooftop solar, up from about 5GW in 2015 and that battery storage would have grown to 34GWh from zero.