CANBERRA, July 17 (Xinhua) -- Australia's independent energy market operator has called on the nation's coal-fired power plants to operate for at least 20 more years.

In a report commissioned by the Coalition of Australian Government (COAG) and the Australian Energy Market Operator (AEMO) on Tuesday recommended that the fleet of coal-fired plants be allowed to run for as long as possible.

It found that replacing the generation capacity of the coal-fired network with renewable sources by the mid-2030s would cost between eight and 27 billion Australian dollars (5.9-20 billion U.S. dollars).

According to the report, extending the lifespan of the coal-fired plants as long as they were economically viable would be the least-cost option for the transition to renewables.

However, AEMO stopped short of recommending that new coal-fired plants be opened.

The report is a significant boost for Prime Minister Malcolm Turnbull who has been in favor of a slow transition to renewable energy.

The AEMO report suggested that coal-fired power would deliver a reliable baseload of power while Australia transitioned to renewable energy.

Immediate action is required to maximize the economic use of existing low-cost generation. Also, investment is required to facilitate the development of projected new renewable resources to replace retired and retiring resources, and to provide essential system security, the report said.

"Conventional generators have also traditionally been relied on to provide essential grid security services, such as inertia, system strength, and frequency control."