Construction activity in the energy sector had made strong gains, forecaster and analyst Deloitte Access Economics said in its latest Investment Monitor report.

"The value of work commenced doubled over the past year as construction continues on two large projects: The $300 million Cattle Hill and the $280 million Granville Harbour wind farms," Deloitte said.

"The pipeline of engineering work is led by the proposed $576 million replacement of Bridgewater Bridge, but major works aren't set to start until 2022.

"There's also a healthy pipeline of renewable energy generation projects, led by UPC Renewables' Robbins Island wind farm."

It noted development of some of the energy projects might depend on the construction of a second electricity interconnector cable to the mainland.

Deloitte said the value of work done in the state's commercial construction sector grew in the past year.

It said construction of the $689 million Royal Hobart Hospital redevelopment was expected to end in mid-2019.

"Work is set to start this year on the University of Tasmania's $400 million science and technology precinct, as well as the new $270 million northern prison," Deloitte said.

Planning was under way for a 172-room hotel at MONA, to potentially cost $400 million.

"The University of Tasmania is also progressing their $300 million Northern Transformation Project, which will include new campuses in Burnie and Launceston," Deloitte said.

"And, with that healthy pipeline, there's the potential for activity to pick up notably in coming years."

It said the state had nearly $3.5 billion worth of projects under construction, a 9.8 per cent increase in a year.

Nearly $3 billion worth of further projects were under consideration, with $1.26 billion more rated as possible.

The report covers engineering construction, non-residential building and equipment investment projects costing $20 million or more.