The rollout began in February on the new South West Rail Link and last week Transport Minister Gladys Berejiklian announced more than 20 Opal card top-up machines had been switched on in Sydney.

Stations with the machines now installed include Parramatta, Wynyard, Redfern, Central, Town Hall and Bondi Junction.

The government plans to introduce almost 350 Opal card top-up machines on stations across the network, which Ms Berejiklian said would provide coverage "for about 99 per cent of customers".

At the launch in February, Ms Berejiklian said the machines would pop up on Illawarra stations "some time this year".

Despite the rollout progressing, there is still no clear timeline for when Illawarra commuters will be able to use the machines.

"There will be top-up machines at stations in the Illawarra and customers will be advised on the timing and locations closer to the rollout," a spokesman for Transport for NSW said.

The first 100 machines rolled out will use credit and debit cards while later machines will also accept cash and dispense disposable tickets.