Rooftop solar is emerging as the latest threat to South Australia's energy system security, as network operators and suppliers predict that it could soon on some days supply the state's entire energy needs.

Key points: Growing number of homes with rooftop solar panels pose challenge in keeping grid stable

Growing number of homes with rooftop solar panels pose challenge in keeping grid stable Trials underway to explore ways of including battery storage in future energy mix

Trials underway to explore ways of including battery storage in future energy mix SA Energy Minister calls on Federal Government to create combined climate and energy policy

One in four South Australian homes already have rooftop solar panels, and the numbers are growing.

South Australia completely lost power on September 28 this year, when storm winds toppled transmission lines.

It triggered a chain reaction that knocked nine windfarms out of the grid, and cut the state's connection to Victoria's backup power supply.

But as repairs continue, the company that owns the state's power transmission network, ElectraNet, has warned the latest risk to system security is not the weather but rather the anticipated massive uptake in solar and batteries.

It said the state was at its most vulnerable to another blackout event on days of "minimum demand" — when people are using the least amount of power and all of that power is being drawn from solar.

Matthew Warren says nobody "really planned" to get the levels of renewables currently in South Australia. ( ABC News: Alex Mann )

"It could be as early as 2023 when the energy coming from rooftop systems in South Australia is all the electricity that state needs to run the grid," Australian Energy Council chief executive Matthew Warren said.

"While that's interesting, that poses technical challenges in how we keep the grid stable."

Mr Warren represents existing energy suppliers and retailers.

Their challenge is how to pay for a grid that is increasingly being used as a backup, as energy users switch to a mix of solar and batteries.

Mr Warren said it was "an accidental experiment".

"We know we have to decarbonise our energy systems, we know we have to use more renewables — but no-one really planned to get to the levels of renewables that we have in South Australia right now," he said.

SA Government's solution could push more people to solar

Across Australia, trials are underway to explore ways of including battery storage into the future energy mix.

The goal is to reduce the need to spend more on infrastructure, and to increase energy security.

In the short term, that does not reduce the risk of those days of minimum demand, and Mr Warren said the state still needed a secure power source.

The State Government's solution to energy security could push more people to solar and batteries. ( ABC News: Alex Mann )

"You can't simply rely on an interconnector for all the system security," he said.

"If the interconnector drops out, or there's a fault, or whatever happens to it, there is no system security — there is nothing regulating frequency and voltage in the grid."

Mr Warren said the State Government's solution — more gas-fired generation, or a second interstate connection — could actually push up prices, pushing even more people to solar and batteries.

"Most solutions, by definition, tend to push up prices, because if they were cheaper we would do them anyway," he said.

Calls for national climate and energy policy

South Australian Energy Minister Tom Koutsonis admitted he had few powerful levers he could pull, and has called for the Federal Government to create a combined climate and energy policy.

Storms toppled transmission lines in September, causing all of SA to lose power. ( Lateline )

"Without that national framework, you are going to get these perverse outcomes," he said.

In two weeks, he will take his call for reform to the Council of Australian Governments (COAG).

"Talk is cheap — it is now time for national leadership," he said.

"It is now time for the Prime Minister to get serious about bringing climate policy and energy policy together."

The Federal Government has commissioned its chief scientist, Alan Kinkel, to look into energy security, and will deliver a preliminary report by the end of the year.

Federal Energy Minister Josh Frydenberg said he would await the findings of Dr Finkel's review, but was happy with the current policy settings.

"If the State Government has a complaint then maybe it needs to look in its own backyard," he said.