Jun 23, 2025
The Promise and Unseen Costs of Underground Power Transmission
Underground transmission lines (UTLs) seem like an obvious solution to large areas of the grid being destroyed by adverse weather. But everything we do has the potential to create unintended consequences. Such was the impetus behind a study looking at the impacts of underground power transmission on the soil. The study was published last summer.
Researchers were primarily interested in knowing whether UTLs generate heat during normal operation. And if they do, is that heat enough to negatively impact soil temperature and moisture content? Because if it is, underground transmission could affect agriculture. It could also upset the delicate balance of certain ecosystems.
Rebuilding Germany's Grid
Without getting into all the study's details, Germany's ongoing effort to rebuild its grid partially inspired it. As the European nation seeks to meet sustainability goals, leaders want the grid rebuilt in the most environmentally responsible way possible. Underground transmission is on the table.
For their research, the team chose a number of test sites featuring high voltage cables buried at various levels in the ground. They monitored the amount of power flowing through the cables along with soil temperature and moisture levels at various depths. They discovered some interesting things.
First, UTLs generate the most heat under the heaviest loads. The more power flowing through a cable, the more heat is generated. Fortunately, whether the heat escaped was largely based on the quality of insulating material surrounding a given cable. Better insulated cables released less heat into the soil.
Limited Impacts on Soil
Researchers also observed that while the UTLs did contribute to elevated soil temperatures and less moisture, the impacts were limited. They also noted that the impacts were most profound in the soil immediately surrounding a cable. And the deeper a cable was buried, the less impact it had on temperature and moisture levels.
The good news is that we now know more about underground power transmission. We know that it generates heat that gets absorbed by the soil. But we do not know the long-term impacts. The German researchers said their results are not conclusive. They said more research is necessary to fully understand the ramifications of burying power transmission cables underground.
Why It is Attractive
While Germany is rebuilding its power grid, utilities and municipalities worldwide are taking a serious look at underground transmission. It is very attractive for obvious reasons.
Here in the States, we experience some of the most climatologically diverse environments on Earth. In the Southeast and Gulf Coast, hurricanes wreak havoc on above-ground transmission lines every season. Winter storms threaten power transmission lines in the northeast and upper Midwest.
In America's heartland, tornadoes are the big threat. And along the west coast, it is a combination of severe winter storms, wildfires, and earthquakes. There is not a location in the continental U.S. that does not face some sort of natural threat to the grid. That is what makes underground transmission so attractive.
Burying Lines Solves the Problem
Burying transmission lines underground all but solves the problem presented by storms and earthquakes. But underground transmission is more costly to implement. It is also more costly from a maintenance standpoint. The question is whether or not we would actually save money by not having to rebuild the grid every time a severe storm destroyed above-ground lines.
While utilities and municipalities continue looking at dollars and cents, researchers will have their plates full with investigating any potential environmental impacts. What they learn over the next few years will likely play a pivotal role in the future of underground transmission.
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