Records for solar were set in Victoria, NSW and South Australia in the first three months of 2023, according to the latest report from the Australian Energy Market Operator (AEMO).

AEMO chief executive Daniel Westerman said the data reinforced the need for critical transmission investments to share low-cost, low emission renewable energy with consumers.

Gas had the largest percentage drop, down one-fifth compared to a year ago, to its lowest March quarter level since 2005, the report released on Friday showed.

Coal-fired generation remained the largest contributor at 58 per cent, while renewable energy contributed 37 per cent.

Black coal generators in NSW and Queensland offered more power into the system at lower prices after state governments put controls on thermal coal costs capped by their state governments to control soaring energy bills.

Wholesale spot prices averaged $83 per megawatt hour during January to March, down from $93/MWh in the final three months of last year and $216/MWh in the September quarter of 2022.

The report also recorded a record March quarter low for greenhouse gas emissions at 28.83 million tonnes, down 5.1 per cent on a year earlier.

There was record average output of rooftop solar (2962 megawatts), up almost a quarter (23 per cent) on a year earlier, which contributed to the lowest operational demand (14,375 MW) since 2005.

Increased solar output reduces operational demand by lowering the supply required from the grid.

Despite easing weather conditions and relatively mild temperatures, price differences continued between states, the operator said.

Northern regions of Queensland ($104/MWh) and NSW ($101/MWh) had higher average prices than the southern regions of Tasmania ($80/MWh), South Australia ($72/MWh) and Victoria ($56/MWh).

But price expectations are falling, with forward prices for the 2023/24 financial year averaging $107/MWh across the four mainland market regions.

Contracts had spiked to $230/MWh for NSW before falling dramatically in December following federal government intervention.

East coast wholesale gas prices eased to an average of $11.86 per gigajoule, still above $9.93/GJ a year ago, after the emergency price cap of $12 was put in place.

Each year, regulators estimate the costs retailers face when supplying electricity to homes and small business customers in South-East Queensland, NSW and South Australia.

A final determination is due next month, with changes to be applied from July 1.