​Rebidding activity in the NEM has exploded in the past few years, thanks to battery autobidders constantly submitting revised bids hundreds of times per day. Revising bids as market conditions and forecasts change is essential for optimisation. The rise in rebidding has brought increasing attention on the practice from asset operators, as well as market regulators concerned about the risks for anti-competitive outcomes.

This report examines the bid data for grid-scale batteries in the NEM. Based on the data, this report then analyses how different autobidders perform in capturing merchant revenues.

​Executive summary

• Batteries have driven a significant increase in rebidding activity. Daily energy bids in the NEM have increased from 5,000 per day in 2021 to 30,000 per day in 2025.
• Frequent rebidding does not result in higher capture rates. Revenue optimisation relies on accurate forecasts of market conditions, not on the frequency of rebids.
• Assets using the same autobidder can have very different results for revenue optimisation. Asset owners need to consider not only their autobidder, but also site-specific factors affecting bidding strategies.
• Late rebids submitted close to dispatch are essential for optimisation. Most batteries shift capacity into lower price bands to ensure that they are directed to discharge.

​NEM units can revise their market bids to respond to changing conditions

Units in the NEM bid to provide energy and frequency control by dividing their available power output into ten different price bands, both of which they set themselves. Units can submit bids for a five-minute interval multiple days in advance. But they can also revise their bids for that interval up until the start of the interval itself by submitting a new bid. This process is known as rebidding.