People power: How rooftop PV now rules roost over coal in the midday sun

It is less than two years ago when a first occurred for the Australian grid – the amount of rooftop solar generated on the homes and businesses of ordinary Australians overtook the output of the country’s coal fired generators.

On that occasion, at precisely midday on October 10, 2022, the difference in output was 953 megawatts (MW). What has happened since is equally remarkable – rooftop solar now out-generates coal on nearly a daily basis, and this week the gap between the two technologies reached a new peak of 5,677 MW.

That new record was set on Wednesday, at 12.25pm, when rooftop solar hit 13.2 gigawatts (GW), and the combined output of coal generators sunk to 7.5 GW.

It highlights the extraordinary shifts that are occurring in Australia’s electricity grids, and the key role that consumers – be they households or businesses – are playing in the transition, even if they are adding just a few kilowatts of PV to their rooftops.

This graph below – courtesy of Geoff Eldridge from GPE NEMLog, which has kept tracked of these new records – show how in the past week rooftop solar has out-generated coal in the middle of the day.

That gap will grow as consumers continue to add between 2 gigawatts and 3 gigawatts of new rooftop solar each year: The Australian Energy Market Operator predicts the amount of rooftop solar capacity will grow four fold to some 86 GW in coming decades.

That, of course, has an impact on the rest of the grid. It will mean no room for so-called baseload or “always on” generators, because there would be no demand need for their output at those time.

The heads of all the big generator companies in Austalia, particularly those running the remaining, ageing coal fired power generators, acknowledge that the era of “baseload” is coming to an end.

That’s not recognised by the Coalition, the nuclear lobby and the anti-renewable agitators. But it remains one of the big unknowns about the Coalition’s nuclear plan for instance – if nuclear is to be “always on”, as they insist it must, what then happens to rooftop solar?

It also points to the need for more flexible and easily dispatchable capacity, and for storage, which can soak up excess solar in the middle of the day and ensure that it is fed back into the grid in the evening peaks.