Sanjeev Gupta, who is spending more than $2 billion on clean energy and green steel developments in regional South Australia, said he also had thought about investing in coal generation in SA's Upper Spencer Gulf after buying Arrium's steel mill last year, but solar backed by firming storage technologies made better economic sense.

Gupta said it was still the perception that it was cheaper to make power from coal than it was from renewables, however, that was no longer the case.

"It was the case not long ago, but it's no longer the case, and we will prove it," he said.

Gupta also plans to build an electric car plant in SA or Victoria and produce 30,000 vehicles a year, and a copper smelter and refinery in SA.

The federal government is considering boosting support for coal power, as part of its proposed national energy guarantee policy, and some Coalition MPs have even called for taxpayers to underwrite or subsidise coal-fired generation.

The Australian Energy Market Operator predicts renewable electricity backed by storage and gas will be the cheapest replacement for the existing coal fleet, however, it said it would be vital to avoid early departures from the electricity grid to ensure an orderly transition.

Gupta, through his family-owned GFG Alliance group of companies, bought the Whyalla steel mill in 2017 off the administrators of its former owner Arrium.

Since taking over Gupta has spent at least $1 billion and doubled the steel mill's annual output to 2 million tonnes, by focusing on recycling scrap steel and investing heavily in 13 clean energy projects around Port Augusta and Whyalla.

These include two farms of solar photovoltaic panels to run the steel plant and feed into the national grid; a co-generation plant to capture waste gases from steel production and convert them into electricity; and three pumped hydro plants in disused mining pits in the Middlebank Ranges.

Gupta said the $700m electricity plan he revealed year was likely to expand to about $1.5 billion, as the new projects were included.

He also recently bought the Tahmoor metallurgical coal mine in New South Wales, and took a majority share of solar and battery firm Zen Energy.

Gupta said while he believed the long-term future was renewable energy that alone would not have been enough to persuade him to invest in it.

"If it was cheaper to make new coal plants, I would argue you should invest in that technology… these HELE [high efficiency, low emissions] plants are incredibly efficient these days and their emissions are really quite impressive," he said.

"But it should just turn on what's more competitive. If you can make power from the sort of things that we're doing and it can compete against a new coal plant, then why would you not do that, right? It's obvious."

Gupta said Australia remained well behind other countries in the transition to a cleaner economy, because its high electricity prices were crippling for industrial players.

He said there also had not been enough investment in new generation, and some older generation had gone away.

Gupta believes thermal coal will remain a major part of the global energy mix for years to come, and it will take at least a generation to phase it out.

 "The future is definitely renewable," he said.

For Gupta,  Australia does not have enough entrepreneurial companies and large public corporations focused too much on short-term thinking because shareholders expected immediate returns and boards were designed to meet their needs.

He said it was not possible to have a three-to-five-year return on solar power.