Some of Australia’s biggest and best known solar farms have suffered significant downgrades to their output ratings in the market’s latest assessment of grid congestion and energy flows.
The latest assessment of marginal loss factors – which measure line losses between the point of generation and the regional reference node – reveal cuts of more than five per cent for a number of significant solar projects for the 2026/27 year, but some small gains for others.
But some big battery projects are benefiting from the changes, with favourable reductions in input ratings and increases in output ratings, which will make the economics of their operations a lot better.
To some extent, MLF ratings can be a bit of a raffle, given that they can be changed by the creation of new load (industries) in certain areas, and the shutdown, or construction, of competing generators, and the building of new power lines. But good planning does help.
The latest draft assessment, this time for the 2026-27 financial year, published earlier this week by the Australian Energy Market Operator, reveals mostly minor changes to the bulk of generation and load, but solar farms in NSW, mostly in the south-west, and in central and northern Queensland, suffer the most.
AEMO says that in Queensland, the changes are driven primarily by new generation capacity in central Queensland and an increase in the output of existing generation. It says this has resulted in increased southerly flow toward the regional node – i.e. more competition.
That has affected solar farms such as Lilyvale, Longreach, Kidston, Haughton and Hamilton, most of which have suffered cuts in their MLF ratings of up to five per cent.
However, planned generation outages in south-west Queensland have led to small increases in MLF ratings for facilities in south-west Queensland and in northern NSW.
The worst affected facilities are solar farms in NSW, mostly in the south west, where MLF ratings have been cut by more than five per cent for more than a dozen solar farms.
These include the Walla Walla, Wagga North, West Wyalong, Junee, Hilton, Griffith, Glenellen, Corowa, Culcairn, Limondale and Sunraysia solar farms – the latter two having their MLFs cut to a shade above 80, meaning that one fifth of their potential output is lost in transmission.
AEMO says the causes of these changes are new generation capacity, and variations in the diurnal nature of flows on the main transmission lines from Victoria to NSW, and the first operations of the new connector between South Australia and NSW, as well as more local generation.
The diurnal issue is important, because it points to the fact that solar is produced at the same time, so has more competition as it seeks access to the areas where it is needed. It is why wind MLFs have mostly barely budged, because they mostly generate in the evening.
“This year’s draft MLF outcomes continue to reflect an energy system in transition, shaped by the introduction of new renewable generation and storage projects, changes in the timing and location of dispatch, and transmission developments such as Project EnergyConnect Stage 2,” AEMO says in its report.
“These changes influence local energy flows, but the overall year-on-year movements in MLFs are well within historical averages, including in regions that have seen the largest shifts such as northern Queensland, south-west New South Wales and northern Victoria.”
In Victoria, the variations are less marked, with the Numurkah, Glenrowan and Girgarre solar farms faring worse, but the Carwarp and Bannerton solar farms in the north-west doing better, mostly because they have more access to the NSW grid thanks to the new link from South Australia which has a spur line into Victoria.
Source: AEMO.
But the biggest beneficiaries are Edify Energy’s co-located Riverina and Darlington Point big batteries, and the new Limondale battery (the country’s first eight hour storage facility), which have all experienced significant reductions in input MLFs, and big increases in output MLFs.
RWE’s Limondale battery, for instance, has its input rating cut to 0.8544 from 0.9280, and its output rating lifted to 0.9503 from 0.9237, largely because of its ability to time its charging and discharging.
This is good news on both counts, and reflects the need for storage in areas with grid congestion and a lot of solar.
The message is clear – solar farms need to come with their own big batteries, and this underlines the major new shift towards solar-battery hybrid projects, where batteries can absorb the excess solar output behind the meter, without affecting MLFs.
In fact, these MLFs are likely to be improved because batteries can choose their time of discharge, usually in demand and price peaks when the grid traffic is lower, and when the grid is not subject to blockages..
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Giles Parkinson
Giles Parkinson is founder and editor-in-chief of Renew Economy, and founder and editor of its EV-focused sister site The Driven. He is the co-host of the weekly Energy Insiders Podcast. Giles has been a journalist for more than 40 years and is a former deputy editor of the Australian Financial Review. You can find him on LinkedIn and on Twitter.
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