Plans to transform the NSW energy system and replace coal-fired power is proving to be more costly and will take longer than initially thought.
Energy Minister Penny Sharpe briefed journalists about Labor's network infrastructure strategy, saying she was concerned that costs and time frames had grown since the project was proposed in 2020.
"I want to be very upfront about this, there's some real challenges within this plan," she told reporters on Thursday.
"The previous government was asked about costs and time frames and never provided an answer."
The network infrastructure strategy, due to be released later on Thursday, is the first time any detailed costings have been made and estimate the total cost to come in just under $10 billion.
"It's not a small amount of money," she said.
"(In 2020) we had some back of the envelope suggestions about how long these projects will take and how much they would cost.
"So the increase has been substantial and I am concerned about that."
The renewable energy roadmap, drawn up by the previous coalition government, had been made more difficult by the "addiction to privatisation" in the energy sector and original time frames did not include the need to consult local communities, Ms Sharpe said.
The two renewable energy zones that account for the bulk of the new generation capacity will be delayed by up to two years.
The central west Orana zone, covering almost 21,000 square kilometres with a network capacity of 4.5 gigawatts for new wind and solar projects at a cost of $3.2 billion, will not hit its "energisation date" until 2027-28, compared with an initial 2025 target.
The New England zone, covering almost 15,500sq km with a network capacity of 2.4GW and at a cost $4.2 billion, will now start in 2029 - two years behind the initial 2027 goal.
The government plans to reform the state's energy systems, transitioning from fossil fuels to renewable energy with a clean energy target of 50 per cent renewable energy by 2030 and as close as possible to 100 per cent by 2050.
The government said it will also commission an independent check-up on NSW energy policies to ensure a timely and cost-effective transition of the electricity sector.
Energy and public policy specialist Cameron O'Reilly will conduct the work in stress testing electricity supply and reliability supported by an expert advisory panel.
Ms Sharpe said the check-up "will help us identify what else we need to do to remove barriers to delivery and accelerate getting infrastructure into the ground".
A report will be delivered to the government in early August 2023 and made public.
The coalition committed to a $1.2 billion investment under the Transmission Acceleration Facility to expedite critical energy infrastructure, create renewable energy zones, drive private investment in renewables, upgrade the transmission network and boost energy storage.
The 10-year investment would cover the initial planning and development stages until construction began by private operators who would then pass on costs to consumers.
