TORONTO -- Toronto Hydro has submitted a five-year rate application it says it needed to invest in the city's aging electricity grid.

The plan calls for $4 billion in funding to replace aging assets, meet growing demand, improve reliability and safeguard against extreme weather events.

If approved, the plan would raise the total bill for residential customers by about $3.54 per month for the average household -- for each of the next five years.

For 2015, the plan calls for a rate increase of just over 2.5 per cent, or $3.10 per month for the average household.

The application is subject to approval by the Ontario Energy Board.

Toronto Hydro delivers electricity to about 733,000 customers in Toronto, making it the largest municipal electricity distribution company in Canada.

President and CEO Anthony Haines says a significant amount of the grid is past its life expectancy and needs to be replaced.

"We've developed a five-year plan to make strategic investments into our aging grid, with a focus on strengthening the grid and improving reliability," he said.

"It's a long-term plan to invest in the grid gradually to spread out costs and ease rate pressures."