The Crown utility is asking the province's public utilities board for hikes of 3.95 per cent both this year and next.
The utility has already said it needs such increases every year for the foreseeable future in order to fund new projects and replace aging infrastructure.
In documents filed with the board, Hydro says any increase smaller than 3.95 per cent could hurt the province's credit rating, because Hydro would have to go deeper into debt backed by the province.
Lower credit ratings can force governments to pay higher interest rates on their borrowings, and the Manitoba government has already been warned its rating could suffer.
Last fall, Moody's Investor Services maintained the government's credit rating at Aa1, but switched its outlook from stable to negative, due to a string of deficits that started in 2009.
Documents filed with the utilities board say Hydro's debt, at almost $11 billion, accounts for more than one-third of the total provincial debt.
"Debt advances to Manitoba Hydro form a significant portion of the total provincial debt and the corporation’s financial performance is therefore a contributing factor toward the financial strength and stability of the province's credit rating," Hydro's application reads.
In the legislature, Opposition finance critic Cameron Friesen called the proposed rate hikes "massive", but the minister responsible for Manitoba Hydro said the rate hikes will allow Manitoba to expand and continue to be self-reliant for electricity.
"We're making the right investments today so that Manitobans can have a low-cost, reliable source of homegrown energy for decades to come," Eric Robinson said.