SA mega-battery 'not great capacity'

Barnaby Joyce has dismissed South Australia's plan for the world's biggest lithium ion battery as a good idea but too small to make much difference.

Billionaire investor Elon Musk's company Tesla will build the 100 megawatt battery - paired with a new wind farm from French company Neoen - within 100 days, or deliver it for free after signing a deal with the SA government.

But the acting prime minister said people shouldn't think this is going to be the power solution for the state.

"It's a good idea but the capacity is not there," Mr Joyce told ABC TV on Sunday.

"You know, a grain of sugar is an advantage to a teaspoon, but it doesn't make a hell of a lot of difference."

He cautioned against thinking "coal-fired power is an evil word" and lauded his government's plan to build larger storage capacity through expanding the Snowy Hydro scheme.