Gas peakers are used all around the country. Many of them were built decades ago to support coal when it couldn't manage peaks or when it broke down unexpectedly.
SA ran out of a coal supply. It doesn't have a coal resource like the east coast states so it had to find an alternative.
Thanks to 9 years of a failed federal COALition, SA was left to sort out it's issues on it's own.
As the chart clearly shows, SA is using less and less gas for generation over time. It is well on it's way to no fossil fuel required. By the end of the decade, SA will be a net electricity exporter.
