Households lose up to an hour of solar power as network tests rooftop PV switch-off

Solar households in South Australia may have missed out on up to an hour of power from the sun on Thursday, as part of “intentional testing” of the state’s solar curtailment mechanism, used to remotely switch off or dial back rooftop PV exports.

SA Power Networks said on Thursday in emails and on its website that it was conducting tests of the Smarter Homes PV curtailment system, which aims to ensure the state’s rooftop solar systems can “ride through” grid faults, be subject to changing export limits, or switched off if needed to keep the system stable.

“During this testing, customers with rooftop photovoltaic (PV) systems connected after 2020 (including Flexible Exports systems) may experience a temporary impact on their solar power generation for one hour during daylight hours,” the SAPN notice says.

South Australia’s Smarter Homes regulation came into effect in 2020, requiring all new residential rooftop solar systems to be able to disconnect and reconnect from the grid via a third party “relevant agent,” as and when directed to by the Australian Energy Market Operator.

SAPN describes it as a tool of last resort, invoked “very rarely and in most cases [in a way] that not noticeable for customers, as all that happens is the customer’s solar system stops exporting for a period of time.”

For South Australia, this might be when the state’s electricity system is separated from the national grid, as was the case in November 2022 when heavy storms brought down at least one transmission tower and caused multiple transmission lines to trip.

But as Gabrielle Kuiper explains here, disconnection doesn’t just put a stop to exports. For most systems it also means the household cannot consume its own solar generation behind-the-meter, requiring consumers to purchase electricity from the grid uncompensated. And that’s where it gets controversial.

Happily, there are other options, including the introduction of flexible exports, which allows rooftop solar systems to be ramped up and down to better suit the needs of the grid, particularly at times of minimum demand.

And while experts argue that more modern engineering solutions like flexible exports should remove the need for a big solar button, AEMO is still pushing for emergency switch-offs to be implemented across the country’s main grid, to better control the around 20GW of rooftop PV already installed.

“That’s more than seven Eraring power stations at full output, and capable of meeting almost half [48%] of our energy demand when the sun is shining at its brightest,” Westerman told an energy summit last year.

“And having so much generation that doesn’t respond to market signals or operational signals, can sometimes be a challenge.”

So far, the South Australian, Western Australian, and Queensland governments have each implemented solar management programs that enable some rooftop solar systems to be switched off remotely in extreme conditions to protect grid stability.

Victoria was due to introduce its own emergency backstop mechanism for small and medium rooftop solar systems in July, but extended the start date to October “to support a smooth transition to the new requirements.”

For SAPN – whose bleeding edge grid has, on occasion, seen rooftop solar meet all of the state’s electricity demand – testing of its Smart Homes curtailment system is necessary, it says, to ensure the switch-off button will work, if pushed.

“We understand the importance of solar energy to our customers and the environment, and we have taken all necessary steps to minimise the duration of this impact,” the network company said on Thursday.

“We sincerely apologise for any inconvenience this may cause and appreciate your understanding as we work towards enhancing the stability and efficiency of the network, including this emergency capability.”