The two hurricanes that blasted through Florida over the past month left a trail of destruction, but they didn’t leave a clear answer on whether burying power lines will prevent serious damage to the grid.
Florida Power & Light officials and leaders from central Florida cities like Winter Park sang the praises of undergrounding power infrastructure after their buried lines experienced less damage than overhead lines and minimized outages during Hurricane Milton, which hit Oct. 9.
Still, grid experts and other utility providers say undergrounding is not a cure-all for weather-related damage and outages. Duke Energy Florida said buried lines did not perform better than traditional lines during Hurricane Helene, which struck Sept. 26. Questions about power lines come as utilities juggle efforts to meet rising electricity demand, shift to cleaner generation sources and keep prices from rising too quickly.
“When it comes to protecting infrastructure, you have the unfortunate reality that there is no place you can locate infrastructure to shelter it from all types of environmental hazards,” said Ted Kury, director of energy studies and the Public Utility Research Center at the University of Florida.
Underground lines can be damaged in floods and washed away in hurricane storm surges, he said, while aboveground lines can fall victim to flying debris and falling trees. The key, Kury said, is strategically planning where underground infrastructure may pay off and where above ground lines make sense.
Florida Power & Light CEO Armando Pimentel said he was all in on continuing to put lines underground as crews worked to restore electricity to millions of customers in the wake of Hurricane Milton, which hit Oct. 9.
At a news conference three days after Milton — a Category 3 storm that slammed the shoreline just south of Tampa Bay — Pimentel said the lines buried underground performed “about 12 to 13 times better” than those above ground.
“Because of that [performance], we will absolutely continue to make that investment,” Pimentel said.
Florida utilities have been especially focused on this type of planning and grid resiliency efforts for decades, sparked by the 2004 and 2005 hurricane seasons that saw a combined seven hurricanes and one tropical storm cause widespread power outages across the state.
Starting in 2006, Kury said, the Florida Public Service Commission began requiring utilities to share best practices at least once a year and made more transparent company’s plans for dealing with hurricanes and other severe weather threats. Conversations about where and when to bury power lines became more common, he said.
In an inland area such as Orlando, a power provider might say undergrounding is a good strategy, Kury said.
“But in a barrier island or coastal area, where they’re more concerned with the impact of flooding and storm surge, they may not decide burying lines is not a cost-effective decision,” he said.
If a utility provider does decide burying lines could help keep the lights on during storms, it still must weigh the cost to ratepayers, Kury said.
Officials in Winter Park, Florida, located just northeast of Orlando, told a local news station that only about 2 percent of their customers lost power because of Milton — thanks largely to 80 percent of power lines being buried underground. The city’s electric utility plans to bury the rest of its power lines in the coming years.
“Winter Park is one of the only cities in America that has a plan in place to underground their entire electrical system by 2030,” the city says on its electric utility website. “Because the utility is owned by the city, it is able to provide this undergrounding service while maintaining rates that are below the average for the State of Florida.”
Winter Park has a population of about 30,000, which could make its experience different from what officials see in larger cities.
Comparing costs
The Public Service Commission of Wisconsin estimates that that a 69-kilovolt aboveground line costs about $285,000 per mile to install, while underground lines can cost closer to $1.5 million per mile. Those costs, ultimately, are borne by ratepayers.
“The key is to look at a particular area and figure out what the options are for trying to protect against extreme weather — what solution is most cost effective for consumers, because ultimately, they’re the ones paying for it,” Kury said.
Feasibility is part of the conversation too, according to David Tuttle, a research associate at the University of Texas, Austin’s Energy Institute.
Burying lines when building a new subdivision may also make more sense than installing underground lines in already densely populated areas, Tuttle said.
“Imagine going down into an urban neighborhood, where houses are close together and they have power lines hanging in their backyards,” Tuttle said. “Can you imagine trying to go back there and digging a trench? You may be cutting cable TV lines, and gas lines, and sewer lines and things like that. You need to be highly specific about where you want to go do it.”
But even power infrastructure built based on a region’s susceptibility to specific types of weather can still be at risk.
Take Hurricane Helene, a Category 4 storm when it made landfall in Florida.
Less than two weeks before Milton, Duke Energy Florida officials said roughly 6 feet of storm surge from Helene washed away underground power equipment that served 10,000 customers on barrier islands just west of St. Petersburg.
The equipment that remained suffered saltwater intrusion, corroding the guts of some 500 pad-mounted transformers and switch gears, said Ana Gibbs, a Duke Energy Florida spokesperson.
Six years earlier, a nearly 16-foot wall of storm surge water washed away the utility’s aboveground poles around Mexico Beach, Florida, during Hurricane Michael.
“Those were two different types of infrastructure, and in both cases they were taken out by storm surge,” Gibbs said.
And the utility has been reviewing the performance of its grid following Milton.
About 50 percent of Duke Energy Florida’s primary power lines are buried, Gibbs said, and over the past three years the company has replaced 40,000 poles with sturdier materials like concrete and composite.
And as far as repairs went after both storms, it seemed fixing above-ground lines was quicker, Gibbs said. She said it’s harder to find the points of failure when you can’t see the line, but it’s easy to see where a tree fell on an above-ground line.
“For Helene, I can tell you the last 400 customers that came back online were all underground customers,” Gibbs said.
That longer repair time might be worth it in some areas if it helps prevent outages, Kury said, but there’s no way to completely protect power infrastructure from extreme weather events.
“The challenge we run into is that there is no blanket solution,” he said.