Hard on the heels of a "near miss" in July when it narrowly averted widespread blackouts, South Australia was warned on Wednesday night to prepare for an extended loss of electricity in the wake of wild weather.

Described as a once in a 50-year storm, the statewide disruption prompted power companies to warn that users of medical equipment should prepare to use back-ups, and mobile phone users to conserve batteries.

"We are experiencing a state-wide outage which means we have no supply from the upstream transmission network," electricity distributor SA Power Networks told clients late Wednesday.

In an unprecedented development, the state was cut-off from the national electricity network, the Australian Energy Market Operator (AEMO) said "resulting in a state-wide power outage in South Australia". As a result, the entire electricity market in the state had been suspended as it sought to work with electricity transmission company ElectraNet "to identify and understand the severity of the fault, as well as determine a power restoration time".

There were no implications for other states from the extensive blackout in South Australia, the energy market operator said.

The extensive disruption follows the narrow avoidance of widespread blackouts in South Australia in July. At that time, the state government brought pressure to bear on a local power company for an idled power station to be restarted to avoid potential disruptions, following a lack of electricity generated from wind and solar sources at a time when it was unable to "import" sufficient supply from Victoria.

But Wednesday's event will trigger renewed debate over the state's heavy reliance on renewable energy which has forced the closure of uncompetitive power stations, putting the electricity network in South Australia under stress.

Earlier this week, the Grattan Institute warned that South Australia's high reliance on renewable energy sources left it exposed to disruptions. It pointed to the fact that while the renewable energy target had encouraged the development of wind and solar generation, it had the potential to undermine supply security at a reasonable price, because it forced the closure of inefficient power stations without encouraging the construction of the necessary new generation supply sources.

That threat followed a warning of rising power outages due to the pressure to close coal and gas-fired power stations as Australia tried to meet its global carbon reduction commitment given in the the United Nations climate conference in Paris late last year.

This warning by AEMO, which operates the national electricity market, was the first official recognition of the deeper issues to be resolved by the federal and state governments if carbon emissions are to be reduced, due to the limited ability of renewable energy to supply at peak demand times of the day, in particular late afternoon.

These issues are different to those South Australia is battling at the moment. But the increasing complexity of electricity networks, which are dealing with a more diverse location of power generators such as wind farms in remote locations rather than a small number of big power stations, means that at times of stress such as extreme storms which occurred in the state on Wednesday, outages can take longer to resolve .

South Australia relies more heavily on renewable power than any other region in the developed world. This has put it at the forefront of confronting, and resolving, the issues involved — as Wednesday's storm has served to remind its residents.