Slow progress on burying power lines leaves U.S. grid vulnerable to extreme weather

As hurricanes intensify, wildfires spread, and winter storm patterns shift, the combination of extreme weather events and aging grid infrastructure threatens to make energy less reliable for tens of millions of U.S. households. 

Experts say burying power lines underground can harden the electrical system against threats from wind, ice, falling trees, and other weather-related hazards. Yet undergrounding power lines remains expensive and unevenly implemented. One obstacle has been a lack of information about where investments in undergrounding by utilities and communities could make the biggest difference for reliable power supplies. 

In a recent study, Stanford University researchers led by associate professor Ram Rajagopal combined previously non-public and siloed datasets to reveal how the distribution of power lines above and below ground has changed since the 1990s. By combining these data with power outage records, the team modeled how having more power lines underground during recent extreme weather events could have shortened outages.

Patchy progress on burying power lines since 1990

Dense metropolitan areas on the East Coast, parts of southern Florida, and a few southwestern growth hubs were among the first to underground at least a quarter of their power line mileage. The overwhelming majority of power lines remained overhead in most U.S. counties in 1990.

By 2020, some fast-growing suburbs in southeastern and Sunbelt states showed modest increases in undergrounding. For most counties nationwide, however, the median percentage of power lines buried underground remained well below 15%. Large swaths of the Rockies, Midwest and Gulf Coast showed virtually no change.

Where outages last the longest

Each year, tens of millions of Americans experience power outages. While households on average lose electricity for about 4 hours over the course of a year, some outages last a day or even weeks. Many of these longer outages are linked to extreme weather events.

New England’s 2017 “bomb cyclone” 

A nor’easter or “bomb cyclone” that struck Maine, Vermont, and New Hampshire in October 2017 left people without power on average for 27.3 hours per home. The Stanford analysis found that burying an additional 25% of overhead power lines could have cut annual outage totals by 10.8 hours.

California’s 2019 wildfire shutoffs 

Amid dry conditions and strong winds in 2019, more than 3 million Californians lost power when utilities preemptively shut down equipment in high fire-risk areas. The Stanford analysis found that undergrounding an additional 25% of overhead power lines would have cut annual outage totals in the affected area to roughly eight hours from 10.5 hours.

Texas’s 2021 deep freeze 

In February 2021, unusually cold temperatures in Texas left 4.5 million homes and businesses without power for just over 19 hours. The researchers found having 25% more power lines underground during this event also could have shortened average outage times by 2.5 hours. 

Explore the data

You can view more analysis from the Stanford researchers and explore county-level undergrounding and outage patterns in an interactive project developed by the Stanford Doerr School of Sustainability in collaboration with TechSoup. The researchers have made their 2020 data on the proportion of underground distribution power lines publicly available through Stanford’s Data Commons for Sustainability.