Authorities say over 30 gigawatts of new clean power generation will be needed as almost two-thirds of Australia’s coal-fired power reaches the end of its technical life.

The Australian Energy Market Operator (AEMO) has released its draft “integrated systems plan” - setting out five possible scenarios for energy generation and transmission spanning the next twenty years.

“This roadmap calls for nationally significant and essential investments in the electricity system to ensure the system meets its security and reliability requirements with the least cost and lowest regret to consumers,” AEMO chief Aubrey Zibelman said in the report.

The preferred scenario is a change determined by a combination of market forces and federal and state government renewable energy policies and the gradual wind-down of coal-fired power.

The report says coal generators are “expected to leave slightly more rapidly” than assumed in the previous plan from 2018, with 63 per cent of such generation due to come to an end by 2030.

AEMO says rooftop solar capacity is expected to at least double and possibly triple in the next two decades, requiring 30GW of grid-scale energy generation, and between five and 21GW of flexible, dispatchable energy (hydro or battery).

The authority says better voltage control and other power system services will be needed to smooth the transition, alongside a major overhaul of the transmission grid itself.

AEMO’s report identifies over 15 projects - at an estimated cost of $3.1 billion - to augment the transmission grid.

It says successfully completing these projects could lead to benefits including $2 billion in lower fuel costs, $1.4 billion saved in deferred generation capital costs, greater competition in the market and downward pressure on power bills.