By the year 2030, New York City could have so many people straining its infrastructure that it won’t have enough electricity or housing to meet demand and rush hour traffic will last all day.

The city of 8.2 million people must start planning and building now for the expected growth of 1 million more over the next 25 years, Mayor Michael Bloomberg and a panel of experts warned.

In 25 years, rails and roads will be “crammed beyond capacity” and won’t be able to accommodate the swarm of commuters during what is now considered normal rush hour.

Lawmakers must act now to not only expand the road network but also to update the subway system, which was built starting in 1901.

The city will need thousands more housing units. And it has to be affordable – already, more than a third of city renters fork over more than half their income for rent, the group said.

Energy demand could exceed supply by as early as 2012, and by 2030 the majority of the city’s power plants will be more than 50 years old. The city needs to improve efficiency, use alternative energy sources and modernize its grid, which was built in the 1920s.