Minimum system load events

Victorians have strongly supported rooftop solar, with hundreds of thousands of solar systems installed on homes and businesses.

While this helps create a cleaner energy future, sometimes these systems and other generation sources can generate more power than the electricity grid can handle.

This is more likely to occur on mild, sunny weekend days or public holidays, during sunlight hours, when solar generation is high, but the demand for electricity is low and other energy intensive processes are powered down.

This is known as a minimum system load event, and if not addressed, can make the grid unstable and lead to widespread and long power outages.

Minimum system load events are rare, but when they do occur, the Australian Energy Market Operator (AEMO) will take a range of steps to address this supply and demand imbalance.

If these steps don’t address the imbalance, the market operator will then direct distribution networks like us to increase demand on the electricity grid. In some cases, AEMO will be able to forecast an event in advance, while at other times the operator may require us to act immediately.

We will respond to a minimum system load event by adjusting the amount of electricity either being exported or generated into the electricity network or used by consumers. We have systems and processes ready to respond to these rare events. How we do this depends on how much generation needs to be removed.

The actions we may take include:

1. Remotely switching off some large-scale solar and wind farms to reduce the amount of power being fed into the grid.
2. Reducing or turning off solar exports from small scale rooftop solar, including residential solar installed, upgraded, or replaced after 1 October, 2024. This also applies to some medium-sized systems as mandated by the Victorian Government. This is known as the emergency backstop mechanism.
3. Remotely turning on hot water systems at some households to increase electricity demand These systems would typically run overnight.
4. Increasing voltage levels on the network to turn down or off solar systems that are not emergency backstop enabled.
5. As a last resort, we conduct what is known as load shedding. This means we turn off power to customers on a rolling basis, for up to 1-2 hours. We target major powerlines with a high concentration of solar feeding into the grid.

We will only take these temporary steps when directed by AEMO. Once AEMO informs us the event is over, we will return systems to their normal levels.

We always aim to minimise the impact on our customers, but the more generation we need to remove, the more likely customers will be affected.