South Australians have been advised they can return to using power normally, after a fire which knocked out two of the state's major gas generators.

With the Torrens Island and Pelican Point power stations now slowly increasing their output, the Australian Energy Market Operator is no longer forecasting a lack of power reserve in the state.

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Energy Minister Tom Koutsantonis says households can now resume normal use of appliances.

Earlier residents were asked to conserve electricity to avoid potential load-shedding after three units at Torrens went offline following spot fires.

Four spot fires and a possible explosion at the power plant resulted in three units generating a combined 400 megawatts of power going offline at 3:33pm.

The AEMO also reported a loss of 200 megawatts of power from the nearby Pelican Point station, which tripped as a result of the Torrens Island incident.

Load-shedding — ordered by AEMO when power demand outstrips supply — most recently led to 90,000 Adelaide customers being switched off during a heatwave in February.

A Metropolitan Fire Service spokesperson said that on arrival, they found "on-site AGL personnel had extinguished a series of small spot fires using dry power fire extinguishers".

Torrens Island is the state's largest power generator, with a total of eight gas-fired units that generate up to 1,280 megawatts.

It was not clear how many units were in use at the time of the outage and the extent of the damage and time it will take to be repaired remains unknown.

South Australians on tenterhooks over power supply

The reliability of SA's power supply has been a controversial topic since September last year when wild weather resulted in a state-wide blackout.

Another blackout occurred in December, when an electrical fault on the Victorian side of the border prompted the failure of the Heywood Interconnector, which was contributing about 220 megawatts into SA's mix.

SA Power Networks said the cause of the Torrens Island fires was being investigated and did not appear to be caused by its distribution network.

Mr Koutsantonis said the outage was not caused by "some inherent fragility of the system" but was due to fires and the close proximity of large generators to each other.

"The restart is occurring during a very high demand [period]," he said.

"Is it frustrating? Yes absolutely.

"The important thing here now is rather than a blame game is to try and help people, help the market operator manage the system … by keeping the demand low."

Wholesale power prices in SA spiked and hit the maximum allowable limit of $14,000 per megawatt hour.