The CSIRO and the energy market operator say existing coal plants are still one of the lowest cost forms of power but new wind and solar farms will soon be cheaper, even without a carbon price.

The join energy cost report co-authored by CSIRO and the Australian Energy Market Operator also found more batteries would be needed to support the growing level of renewables, and the grid would need to lean heavily on consumers to use less power at peak times.

“Our data confirms that while existing fossil fuel power plants are competitive due to their sunk capital costs, solar and wind generation technologies are currently the lowest-cost ways to generate electricity for Australia, compared to any other new-build technology," CSIRO chief energy economist Paul Graham said.

"This also holds when the cost of fossil generation technology is adjusted for climate policy risk or not."

The report found if nuclear power was built it would be the most expensive form of power, while gas is the cheapest.