Australia will need to build "many more" Snowy Hydro 2.0 projects to balance the massive increase in renewable energy growth, the scheme's operators say.
Snowy Hydro chief executive officer Paul Broad told a Senate Estimates hearing that a lack of transmission infrastructure - the poles and wires - was also impeding the ability to get electricity where it was needed during peak times, such as during summer blackouts. The problem would only get worse once additional capacity came online.
Snowy Hydro has begun work on a multi-billion expansion of its current hydroelectric system in the Snowy Mountains that will see its capacity increase by a further 2000 megawatts, providing an additional 175 hours of storage for the National Electricity Market. That energy will be used like a battery to provide green power during evenings or peaks when solar and wind are not meeting demand.
But officials said that investment would not keep pace with the rapid growth in renewables and was not going to be nearly enough storage to meet demand when other renewables were not generating.
They gave an example of last Friday when renewable power output across the national grid fell from approximately 11500 megawatts during the day to 2500 megawatts that evening.
"That's a swing of 9000 megawatts," Mr Broad told the committee.
"Snowy 2.0 is 2000 megawatts so we're underdone already ... the massive increase in renewables coming into the market is going to demand eight times Snowy 2.0."
Snowy 2.0, announced with much fanfare in 2017 by former prime minister Malcolm Turnbull, has faced heavy criticism in recent weeks for blowouts in cost and construction time, with some experts predicting the project including transmission could be as high as $10 billion to complete.
Mr Broad said a lack of transmission capacity was a serious concern, making it difficult to get electricity to the scheme to where it was needed most.
"To give you context, when blackouts occurred in Victoria last summer we had 1500 megawatts sitting in NSW that we were unable to get to Victoria," Mr Broad said.
"There is a significant amount of transmission required to bring renewables to market and the there is transmission required for existing Snowy ... so it obviously won't be enough for Snowy 2.0," he said.
But Mr Broad hit back at claims the project would damage large sections of the sensitive Kosciuszko National Park where it is based, saying once complete the impact would be about 0.01 per cent of the park's total area impacted.