Con Edison is finishing up a major underground transmission project in Brooklyn that’s expected to boost power reliability.

The 1-mile-long transmission line, which runs between ConEd’s Gowanus and Greenwood substations, is powerful enough to run 300,000 window air conditioners, 400,000 refrigerators or 250,000 toaster ovens at the same time.

“This is increasing the delivery capacity by about 33% to our customers,” said Johnny Price, the project manager.

The $505 million investment includes a similar transmission line on Staten Island. It’s part of Con Edison’s Reliable Clean City program, which aims to prepare New York for growing electric demand, from vehicle charging to electric heating.

“With the increase in electric demand…this is really going to help us continue to provide reliable service,” Price added.

In addition to reliability, the new line will help bring in cleaner energy from upstate, reducing the city’s dependence on fossil fuel plants.

The Brooklyn transmission line is expected to be fully operational by this summer.