Hurricane Ida plunged more than 1 million customers on the Gulf Coast into darkness, and then knocked out power to another 200,000 in the Northeast on Wednesday night. The chief culprit, especially as the storm first came ashore, was the wind — blowing trees, roofs, signs and assorted other debris into the transmission lines, and, in Bridge City, La., knocking down a major utility tower.Heavy rain on already saturated ground also caused utility poles to sag, automatically shutting down the lines they carry.

A way to avoid that does exist: burying cables underground. Electric power in Manhattan — where the lights stayed on despite Ida’s floods — has been channeled underground for years, as it has in other downtown areas across the country. Germany and the Netherlands are moving to put all their lines below the surface.

The chief drawback is the expense. In California, Pacific Gas and Electric resisted calls to bury its transmission lines for years as being too costly. But after the company’s equipment sparked a string of devastating forest fires, it reversed itself in July, announcing that it would bury 10,000 miles of lines that currently run overhead.

The price tag? Somewhere between $15 billion and $30 billion. But the new CEO, Patricia Poppe, told reporters when she made the announcement that doing nothing would cost the company, and the state, even more. “It’s too expensive not to do it. Lives are on the line,” she said.

PG&E filed for bankruptcy in 2019 to shield itself from potentially tens of billions of dollars in liability for forest fires, but emerged from Chapter 11 last year.

Nationally, there are 160,000 miles of high-voltage transmission lines and, according to one estimate, 5.5 million miles of local distribution lines. Mike Beehler, national spokesman for the Power Delivery Intelligence Initiative, a trade group advocating the undergrounding, or burying, of lines, says that in most of the country putting a line underground is easier and less expensive than in California. “The cost of underground is coming down,” he said.

Dominion Energy, based in Virginia, and WEC Energy Group of Wisconsin are each planning line-burying projects, which will result in a total of 5,000 miles of underground wires at an estimated price tag of about $2 billion. That cost, like the PG&E bill, will be passed along to customers. Dominion expects its project to take 10 to 12 years to complete.

Critics say the price is not always justifiable. In an essay for the Conversation, Theodore Kury, the director of energy studies at the University of Florida, argued that in many places overhead lines can be afforded better protection than they now have, for much less money than it would take to bury them. Stronger poles, better anchored, would be one step, he wrote, while aggressive cutting back of vegetation would be another.

Getting access to the lines for maintenance could also be problematic, he added. Beehler, in contrast, argues that maintaining exposed overhead lines can cost three to seven times as much as dealing with those in protective sheaths underground.

John Fluharty, vice chair for the Power Delivery Intelligence Initiative, said that while burying transmission lines is more expensive than stringing them through the air, underground lines do not require repairs with every strong storm that passes through, and over the course of their lifetimes can provide cost savings. He pointed out that going underground doesn’t have to be an all-or-nothing proposition: Utilities can pick the stretches where it would make the most sense.

Overhead lines naturally grow hot as they carry current, and they rely on the air to cool off. Operators must constantly monitor the temperatures of high-voltage lines to be sure they are not overheating. Warmer weather linked to climate change can make that more of a challenge, especially as air-conditioning demand also rises and helps to raise the temperature of the lines.

A technical challenge is in making sure underground lines can remain cool in the enclosed space of a conduit. And as Hurricane Sandy made clear when it hit the New York area in 2012, any underground electrical equipment has to be provided with watertight protection against immersion and the resulting corrosion.