The expansion - previously dubbed SPIRE - was a major election announcement in 2016 when the government pledged it would be open by 2022.

However it has since been plagued with delays, and it's not set for completion until 2024.

The full costings and business case for the project have not been released, but it is expected to cost about $500 million.

Chief Minister Andrew Barr defended the blown out time frame of the project, with construction not due to start until next year.

"This is a case of 'we're damned if we do, damned if we don't," he said.

"If we hadn't have engaged with the community, if we hadn't sought to alter designs to reflect the issues that were brought to us, we would be accused of ramming something through.

"Instead we listened, we consulted, and we adapted and instead the suggestion is we're not delivering the project fast enough."

Mr Barr didn't rule out a cost increase or other difficulties due to the impact of COVID-19 on the construction industry.

Construction contractor Multiplex was the successful bidder to complete the project, which is still in the design stage.

The government revealed it had rebranded the project, which had been dubbed SPIRE since it was announced in 2016.

That name achieved little cut-through with the community, and it will now simply be referred to as the Canberra Hospital expansion.

Mr Barr said the name change was a lesson in clear government communication.

"Calling something what it is is a pretty good starting point to convey what you are endeavouring to do," he said.

Opposition health spokeswoman Vicki Dunne said the Liberals would deliver a "proper" expansion of the hospital if elected, lambasting the government for long delays to the project.

"SPIRE is dead. A decade on and Labor hasn't even figured what to call an expanded hospital, let alone deliver it," she said.

"Under Labor, any hospital redevelopment won't be delivered until least 14 years after it was first promised.

"Despite paying record rates, taxes, fees and charges, Canberrans have suffered the worst-performing health system in Australia.

"Canberrans have been left to wait more than a decade for a desperate upgrade to our hospital to ease pressure in elective surgery and the emergency department."

Mr Barr said the project would stimulate economic activity for the region, creating about 500 local jobs during construction.

In a first for the ACT, the new facility will be an all-electric building. Mr Barr said it would help minimise the carbon footprint of the hospital, improve the hospital's green star rating and support the ACT's target of net-zero emissions.

A development application for the project is expected to be lodged early next year.