Should we bury broadband and electricity together?

Co-undergrounding is the practice of burying both electric and broadband internet lines together. It’s an expensive business, especially if the above-ground lines haven’t reached the end of their usefulness — but could it save money in the long run?

Researchers from the University of Massachusetts Amherst have investigated this question.

In their study, which has been published in the journal Cell Reports Sustainability, the researchers examined several factors that influence the cost of undergrounding lines, using computational modelling across a variety of infrastructure upgrade scenarios.

The co-undergrounding of wires is becoming a salient issue for decision-makers who are focused on the efficiency of infrastructure, according to Erin Baker, faculty director of ETI and distinguished professor in the College of Engineering at UMass Amherst. “Instead of tearing up the road to do this and then a year later tear it up to do that, let’s think about doing it together,” she said.

An aggressive approach

One question posed by the researchers was how aggressively towns should pivot to putting lines underground. Should they wait until lines have reached the end of their lifespan and then replace as needed, or proactively move forward?

To answer this, the study defined three overarching considerations: the cost of converting lines from above ground to underground; the cost of outages; and the hours of outages that can be avoided if lines are underground.

To quantify these factors, the researchers created a nuanced computational model.

“A big driver of this whole thing is the cost,” said Jimi Oke, director of NARS Lab, assistant professor of civil and environmental engineering and principal investigator of the study.

“In previous studies, people just used estimates based on average values, but we essentially try to model the dependency of the cost on things like the soil composition, the network type or the other land use variables,” he said.

Using the town of Shrewsbury, Massachusetts as a case study, the team found that the most cost-effective solution is to be aggressively proactive in co-undergrounding and replacing existing infrastructure — as long as it can be confirmed that undergrounding wires reduces outages by at least 50%.

Over 40 years, the cost of an aggressive co-undergrounding strategy in Shrewsbury was predicted to be $45.4 million, but the benefit from avoiding outages was $55.1 million. This calculation considered factors like spoiled food, damaged home appliances, missed remote work hours and increased use of back-up power sources.

For a power outage, the costs were estimated to be $10 per person per hour, $205 per business per hour and $15,000 per industrial customer per hour. In Massachusetts, the average outage duration per customer per year, for both broadband and electricity, was estimated to be 1.38 hours. The researchers also took into consideration an additional benefit of $1.5 million in increased property values from the aesthetic improvement of eliminating overhead lines.

Altogether, this created a net benefit of $11.3 million, with the study finding that co-undergrounding is 39% more cost-effective than separately burying electrical and broadband wires.

The strategy with the second-highest net benefit was to aggressively convert just the electrical wires from above ground to underground. While this is a less expensive strategy, the savings were notably diminished, for a net benefit that was five times lower than the co-undergrounding strategy. All other strategies, including moderately paced conversions, had a negative net benefit.

The critical nature of outages

What remains to be determined is exactly how many outages will be prevented by undergrounding. “There’s kind of an intuitive thing [that undergrounding will reduce outages], but there is kind of mixed information about exactly how much because there are outages for a lot of different reasons,” Baker explained.

“It means for [undergrounding to be worthwhile] half the outages have to be caused by basically something weather induced. If more than half of your outages are caused by the plant breaking down, then you shouldn’t underground anything. But the moment it flips over and it becomes good enough to do something, it means you want to be fully aggressive.”

Oke pointed out that storms aren’t the only causes of outages — there are also events like the California wildfires. While California utilities will institute planned outages in order to prevent additional fires, putting wires underground could prevent the fire in the first place (and therefore the outage). Consider the 2018 Camp Fire in Northern California — the most destructive wildfire in the state’s history. This fire was caused when a worn-out metal hook on a transmission tower failed, allowing a live line to fall and hit a transmission tower.

“We need to have a framework and a set of regulations that encourages utilities and towns to think strategically,” Baker said, adding that she hoped the teams’ work would help authorities to do this.

The team hopes that future research will quantify the impacts of co-undergrounding across a variety of geographic locations and scenarios. Other relevant future directions include investigating alternative underground routing options, and other potential outage mitigation strategies.

The study authors were Mahsa Arabi, Atanas Apostolov, Abhiraksha Pattabhiraman, Anna Goldstein, Michael Bloomberg, Jay Taneja, Erin Baker and Jimi Oke. Their paper can be read at DOI: 10.1016/j.crsus.2025.100334.

Image credit: iStock.com/gabort71