When the $200 million complex opens on October 9, the developer will control more than 2000 spaces across three car parks, accessed from Market, Keira and Regent streets in the city centre.

On Wednesday, GPT's development manager Steven Turner announced his company would introduce 90 minutes' free parking at all three centres, but only for shoppers who spend more than $20 at the new Coles supermarket.

Mr Turner said the decision to work with Coles and not other retailers was aimed at re-establishing the city centre as a grocery-shopping hub.

"We also expect that the majority of our customers will shop in Coles on some level, so this is the easiest way to manage it and have it benefit a large number of shoppers," he said.

Asked why the centre was not offering three hours of free parking like some shopping malls in Sydney, Mr Turner said he wanted to encourage good turnover.

"We provide the lion's share of CBD parking, so a lot of businesses around the city rely on our parking," he said.

"We need to make sure spaces are available, otherwise our businesses and surrounding businesses would suffer."

He also said market research had shown most people were more interested in a pleasant parking experience than free parking.

"For a long time in Wollongong, people haven't felt like they have got good value for money out of their parking experience from signage, information and the parking environment," he said.

For this reason, two of the new car park levels would have a "real time" parking assistance system installed to direct drivers to the closest available park.

All three car parks will have the number of available spaces displayed at their entrance as well as showing the remaining car spaces on each level.

Additionally, the new underground level has been designed as an "express" level, targeting Coles customers, as it is located directly under the supermarket and other fresh food outlets.