Australia's energy market operator has forecast nearly 80 per cent of homes will be powered by rooftop solar by 2050, potentially reducing the need for investment in "utility-scale" wind and solar farms.

Without better coordination of batteries to store the power being generated, the Australian Energy Market Operator (AEMO) has warned billions more will need to be spent on storage: "increasing the costs that are reflected in consumer bills".

AEMO has released its latest blueprint to decarbonise the power grid by 2050, mapping the transition away from coal to a system dominated by renewables.

Under the plan, all of Australia's coal-fired power stations, producing about 21 gigawatts of energy, will retire by 2038 which is earlier than the operators themselves have forecast.

To replace them and to meet future demand, a six-fold increase in large-scale wind and solar is required but AEMO has warned planned projects are "not progressing as expected" because of slow approvals, community resistance and rising costs.

Given the challenges, some experts tracking the transition have raised doubts about the federal government's ability to reach its target of 82 per cent renewables by 2030.

"Australia's energy transition is well underway, with renewable energy accounting for 40 per cent of electricity used in the past year," said AEMO chief executive Daniel Westerman.

But he warns there's a "real risk that replacement generation, storage and transmission may not be available in time when coal plants retire".

Perhaps acknowledging these problems, AEMO appears to have placed a greater emphasis on households, noting the take-up of rooftop solar, electric vehicles and hot water pumps "has the potential to reduce the need for utility-scale solutions".

Solar and batteries 'slashing bills'

Australians are taking matters into their own hands: about one in three of households has rooftop solar, with a capacity of 20 GW, and that's expected to grow to four in five households by 2050, generating 72 GW of power.

Rooftop solar contributed more electricity to the grid in the first three quarters of this year than large-scale solar, wind, hydro or gas.

Without better coordination of household batteries to store all of that power, an extra $4 billion will need to be spent on large-scale storage: "increasing the costs that are reflected in consumer bills".

The Smart Energy Council – which is represents large-scale renewables companies – has called for a "national battery booster program" to increase uptake.

"A national support program for home batteries will ease the power bill shocks in peoples' homes, further stabilise the grid, and cut pollution."

More transmission lines given green light

Amid a heated political debate about the best way to decarbonise Australia's power grid, AEMO has once again declared that renewables, backed by batteries and firmed by gas, to be the most cost-effective solution.

However, the market operator did not model the Coalition's alternative nuclear power plan because it's not government policy and not currently permitted under Australian law.

The Coalition has not yet released its full policy, but it's been promoting a greater take-up of rooftop solar, amid growing concerns in regional Australia about the massive expansion of large-scale renewables and transmission projects.

AEMO has mapped an extra 10,000 kilometres of high-voltage transmission lines that need to be built between now and 2050 to connect far-flung projects to consumers but several of the projects underway are strongly opposed by farmers.

In this latest blueprint, AEMO has given the green light for another seven transmission projects to be urgently built across Queensland, New South Wales and South Australia.

Time and cost pressures are rising with AEMO estimating transmission costs alone have increased by 30 per cent.

Gas the 'Ringo' star of the transition

In keeping with the federal government's Future Gas Strategy, the report states the small but crucial role gas will play as the safety net of the system, particularly during "renewable droughts" and periods of extreme demand.

AEMO this week issued a "risk or threat notice" for east coast gas supplies following a cold spell, a lack of renewable power and an outage at the Longford gas plant in Victoria – the biggest source of gas in southern Australia.

It warns "further investment will be required" in the gas sector to ensure reliability, including more supply, upgrades and expansions of existing pipelines, import terminals and increased storage.

These statements have been welcomed by the Australian Pipelines and Gas Association's Steve Davies who has used a Beatles reference to illustrate the role gas will play.

"The wind droughts of the past three months in southern Australia have proven the importance of gas generation, and the ISP recognises our grid will get more volatile as the transition progresses," Mr Davies said.

"Solar and wind are the Lennon and McCartney of the transition, while gas is doing its job as Ringo.