Coal, which supplies more than 80 per cent of NSW's electricity, would be the primary source of power generation "for decades to come", Mr Hartcher said yesterday.

The Greens had argued for an accelerated phasing out of coal-fired power, to be replaced by renewable energy, but Mr Hartcher said technology was not sufficiently developed to allow renewable energy to replace NSW's 12,000 megawatts of coal-fired generation.

"This provides some [supply] challenges with the federal government's proposed carbon tax which will make coal-fired power stations increasingly uneconomic to operate," he said in an address to the Committee for Economic Development of Australia.

The minister said in some cases renewables were more expensive than carbon capture and storage for both coal and gas. "Coal provides NSW with a competitive economic advantage and essential energy security that would be irresponsible to overlook," he told The Australian Financial Review.

But the government was "fully committed" to achieving 20 per cent of the state's power from renewable sources by 2020, while gas-fired generation would also increasingly contribute to supply, he said.

But gas-fired power is set to remain primarily restricted to peak-load demand, rather than be used for baseload, continuous supply.