WA's adoption of batteries is supposed to aid its switch from fossil fuels, but it will not be straightforward. (ABC News: Daniel Mercer)
In the wee hours of a cold night last month, as most West Australians slept in their beds, a strange thing happened in the state's biggest and most important electricity system.
About 1am, prices on the spot market started to soar.
They had been hovering at an elevated level of roughly $120 per megawatt-hour (MWh) but suddenly began to climb to extreme highs of more than $350/MWh.
Driving that jump in prices was no catastrophic loss of a high-voltage power line or a major coal-fired plant.
It was a spike in demand and it was coming from an unexpected source.
The surge was coming from batteries, the very things supposedly designed to prevent just such a breakout in prices.
Why it happened — in the middle of the night when there was seemingly no obvious reason — is still unclear.
But experts say the episode highlights how the way batteries are managed will determine their impact on prices as Australia transitions away from fossil fuels.
One person who has been seeking answers is Marcus Freese, an analyst at Modo Energy.
He says a few things are known based on publicly available data.
For one, the batteries that charged between 1am and 2am on July 12 were all owned by state-owned WA power provider Synergy.
Combined, Synergy's four big batteries added more than 30 per cent to demand for power from the grid at a time when prices were already high.
"The market was not tight because of demand or renewable output," Freese wrote in a report.
"Underlying demand was unremarkable for the time of day, in line with the July average for that hour, and wind generation was close to its July average.
