The winning design for the new Powerhouse Museum in Parramatta has been revealed, and criticised, as a "monstrosity on stilts" by the State Opposition.

Two heritage buildings will be bulldozed to make way for the multi-level gallery, which will predominantly be constructed on the site of disused car park.

It will include 60 studio residences which will be available to scientists, researchers and regional students for overnight stays.

But Willow Grove, a 1870s heritage villa that was once a maternity hospital, and St George's Terraces, will be demolished.

Arts minister Don Harwin said while some would be disappointed about that, the new facility would be worth it.

"It's simple, it's cost effective but it's also iconic and fit for purpose," he said.

"It's going to have the largest exhibition gallery of any museum in the country — 20 metres high, column free, 3000 square metres, capable of being opened up to the riverbank becoming a huge stage.

"I think it's an incredible facility."

Labor arts spokesman Walt Secord said the Premier had committed to protecting the heritage buildings earlier this year.

"It's a monstrosity on stilts. It's a monstrosity on two levels — costly and ugly," Mr Secord said.

"The Berejiklian Government was warned about the flood plain at Parramatta and it responded by putting together a Queensland-style flood and cyclone house deep in the heart of Parramatta.

"This project has lurched from crisis to crisis and the winning design is utterly disappointing."

Residential and commercial towers that were at one stage slated to go above the museum have been scrapped.

Last year, the Berejiklian Government confirmed it would shift the Powerhouse Museum at Ultimo to a new home at Parramatta.

The Government said it was confident the project's $645 million budget would not blow out.

Parramatta councillor Donna Davis said it was devastating the State Government had not listened to community concerns about the heritage buildings.

"We do welcome the investment in the city but we thought there would be a bit more vision in terms of incorporating the heritage that we have in our city," the Labor councillor said.

"It should not have been at the expense of Willow Grove and St George's Terraces."