When the government announced an agreement two years ago to proceed with the development, it estimated it would cost $6.2 billion.
But Premier Kathy Dunderdale has recently said the updated cost estimates will be higher.
A news conference has been scheduled Tuesday in St. John's where the new costs and an analysis by Manitoba Hydro International will be released.
Dunderdale's Progressive Conservative government is expected to decide later this year whether to approve the project.
But it is still trying to finalize a federal loan guarantee that could shave hundreds of millions of dollars in borrowing costs.
Critics of Muskrat Falls say the venture is too risky and the province should meet its power needs incrementally.
Dunderdale and Crown corporation Nalcor Energy say they've explored other options but are backing Muskrat Falls.