Minimum stable level values for coal generators

[EllieKallmier]

In version 7.5+ of the IASR workbook, the coal_minimum_stable_level table has three candidate columns that we could use to set the 'default' templated minimum_load value:

• _IASR 2023 (Backcasting)
• _Typical Lowest Band
• _Minimum Continuous Operating Level

For the moment: I set the property merge to use the _Typical Lowest Band column, based on the below copied IASR content. Felt like a bigger call to talk about implementing custom constraints/formulations for using multiple values here - and relates a bit to our discussion the other day about the time-sequential vs capacity expansion detail and complexity - so just went with the static opinionated choice for now.

From the IASR (2025) pages 121-122 (emphasis added by me):

Additional coal generator minimum stable levels
Two new series of coal generator minimum stable levels have been provided in the 2025 Inputs and Assumptions
Workbook:

• Typical Lowest Band – this value is representative of the power level typically offered in the lowest band of a generator’s bid stack. This represents a ‘preferred’ minimum power level, where negative price exposure risk is not material. Across the coal fleet, this is a reduction of 527 MW (6%) in baseline minimum stable levels compared to the previous IASR and is a reflection of growing negative price exposure risk.
• Minimum Continuous Operating Level – this forward-looking value is representative of the minimum continuous power level which the generator could foreseeably offer in their bid stack in response to increasing negative price exposure risk. This represents a ‘tested’ bid at this power level which was dispatched for sustained periods as part of typical generation (not during startup or shutdown) for the specific unit, or it has been observed that most units at the station have demonstrated that capability. Across the coal fleet, the observed potential reduction in minimum stable levels from the current baseline is a 1,317 MW (20.7%) reduction relative to the previous IASR.

The typical lowest band for existing generators is based on AEMO’s analysis of historical generation and operational experience and will be applied in the time-sequential model as a representation of a generator’s typical minimum stable level. The minimum continuous operating level values may be applied in the time-sequential model to represent the future behaviour of coal generators, which is expected to become more likely as coal generators increasingly seek to avoid exposure to negative prices.