Graph of the Day: Negative prices in windy South Australia

This graph caught our eye, tweeted by Simon Holmes a Court of the newly formed Energy Transition Hub, showing negative prices in South Australia this morning.

The negative prices didn’t last long, they really do. What’s interesting about this is that AEMO has not intervened to limit the amount of wind generation, as they sometimes do if they cannot find enough gas generator to switch on.

At around the time of this pricing, South Australia had some 1280MW of wind and about 480MW of gas generation. AEMO had imposed a “constraint” on power coming into the state on the interconnector, but given the wind available that was largely academic.

Intersting to note that Queensland electricity also low at $24/MWh – possibly courtesy of relatively low demand and the more than 1,100MW of rooftop solar powering houses, businesses and being put back into the grid.

Those prices are expected to become more common during the day as the 2,000MW of large scale solar comes on line in the next 12 months. So far, the state has just one 20MW solar farm on line.

Queensland prices have been higher in the last month because of the closure of Kogan Creek for maintenance, with the other state-owned generators taking advantage of the relative “scarcity” to push up prices.

This graph – from the AER’s latest weekly price report – shows that South Australia has had lower costs than Victoria, and actually had lower costs than Queensland too until the state government told the generators to stop gaming the system.

South Australia and Queensland have historically had the highest electricity prices due to the small number of generators and the dominance of two or three energy companies over the market.