The difference of opinion relates to the draft version of a two-year Integrated Service Plan published on December 10 by the Australian Energy Market Operator (AEMO).

On Friday, the Australian Energy Regulator (AER) published its own "transparency review" of the draft plan, which looks at various ways the National Electricity Market (NEM) will change as "coal generation withdraws".

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Under AEMO's "most likely" scenario, the Australian grid will have to more than triple its generating capacity from about 85 gigawatts in 2023 to about 275 gigawatts in 2049.

This is to cope with the loss of coal power after 2038, and to generate enough power to store a surplus - in systems yet to be built - for use each night (when solar is out) and when conditions are too still for wind turbines.

AEMO says electricity use will double by 2050 to cope with electric vehicles replacing internal combustion engines.

A hydrogen export industry would "nearly quadruple" electricity consumption.

AEMO says five gigawatts of the remaining 23 gigawatts of coal power are announced as closing by 2030 but its modelling puts the likely figure at 14 gigawatts, with two-thirds of black coal and all of Victoria's brown coal generation gone by 2032.

In Friday's review, the regulator said AEMO had not "adequately explained how it has derived the large negative profits" - losses, in other words - it predicted coal-fired power stations would make in the coming 10 years.

It said AEMO had "not adequately explained the reasons for assuming" that coal-fired plants were "not expected to operate more flexibly" - varying their output throughout each day - given AEMO's acknowledgement that coal power stations were already "operating below previously observed minimum load" and "adopting different daily load profiles".

AEMO says population-adjusted calculations show Australia added four to five times as much renewable capacity in 2018-19 as the EU, the US or China.

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"The NEM now needs to maintain that record rate every year for the decade to triple variable renewable capacity by 2030 - then almost double it again by 2040, and again by 2050," AEMO says of the transition task.

AMEO said the scenarios in the report were based on detailed engineering and economic modelling with input from various stakeholders including the owners of generating plants.

AEMO said it would respond to the energy regulator's comments when the final report was published.

Submissions are open until February 11.

Details are available on the AEMO website, including registration for an online forum for interested parties on February 1.

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