In the aftermath of a historic blizzard that left more than 300,000 Massachusetts homes and businesses without electricity, you might be wondering why more power lines aren’t put underground.
After all, burying these wires would protect them from the heavy winds, ice and snow-laden branches that frequently cause outages, right?
“It’s certainly the case that undergrounding power lines makes the system more resilient,” said Christopher Knittel, a professor of applied economics at MIT.
But — and this is a big “but” — he said, " it’s just a lot more expensive.”
To put power lines underground, utilities need to tear up streets and sidewalks so they can dig trenches. They need to purchase special insulated wires to make sure electricity doesn’t leak into the ground. And they may need to take down trees with thick roots or remove big rocks that stand in the way.
“An underground system requires entirely different equipment, engineering and construction,” Eversource spokeswoman Olessa Stepanova wrote in an email. “Building that new infrastructure is a significant investment.”
An investment funded entirely by you, the ratepayer.
The actual cost of installing power lines underground varies by location, and depends on factors like the density of housing, how much other infrastructure exists underground and how rocky the soil is.
But in general, putting distribution wires — the small power lines that run along the street and connect to your house — underground can cost two to 10 times more than stringing them above ground, said Johannes Pfienberger, an economist and electrical engineer with the Brattle Group, a Boston-based research and consulting firm.
And undergrounding transmission lines — the large high-voltage lines that carry electricity over long distances — is even more expensive, he said. That work can easily cost 10 to 15 times more than building them above ground.
That’s not to say this work is always cost prohibitive. There are certain places where above ground power lines aren’t feasible, or where the cost of constantly repairing power lines — both in terms of dollars spent and lost productivity — tips the scale in favor of undergrounding.
“In dense city areas, we do have a lot of the wires underground because there’s not that much space — I mean, imagine downtown Boston with overhead wires. It would be very challenging,” Pfienberger said. “But in the suburbs where the houses are more distant from each other, it’s just easier to string wires between telephone poles.”
In 2021, lawmakers in New York who were concerned about weather-related outages directed the state’s public utility commission to study the costs and benefits of burying all or most of the state’s electric, telephone and internet lines.
The results were pretty stark.
Installing a new distribution power line above ground was predicted to cost between $120,000 and $3.6 million per mile. Doing the same project underground would cost $4 to $7.2 million per mile.
While some parts of the state would benefit from burying utility lines, overall the study showed that the effort would cause a net loss of $261 billion statewide. Monthly electric bill would also double or triple for some ratepayers.
At a time when Massachusetts residents and lawmakers are concerned about rising energy costs, it’s hard to imagine giving utilities the green light to put thousands of miles of power lines underground, said Kyle Murray, Massachusetts program director at the Acadia Center.
“If you actually look at your bills, a major driver of those costs is delivery side of things,” he said. “That’s infrastructure. That’s poles and wires. And so undergrounding would just serve to drive that delivery portion even higher.”
What’s more, it’s not like a utility can just put a power line underground and be done with it. Things can, and do, go wrong underground. A buried power line may not get taken out by your neighbor’s precarious tree branch — you know, the one they should have pruned before the storm — but it can be damaged by the guy they hired to drive fence posts in along their property line.
Underground wires are easily damaged by excavators, pipeline repair work or any other number of construction-related activities, Pfienberger said.
They can also be damaged by flooding and, possibly, industrious rodents.
Fixing these lines is also more challenging and expensive than fixing above-ground power lines. Just finding the source of the problem underground can be time intensive, said National Grid spokesperson Bob Kievra. And then the utility has to dig up the line again in order to repair it, which may involve closing down a street or other disruptive activities.
While burying the power lines everywhere isn’t feasible, there are still some places where the effort would be worth it, according to Knittel.
” We don’t have to necessarily move to a system where everything is underground,” he said. “What we really need to do is do a more targeted approach, which is identify the most critical lines in the network and do the cost-benefit test on undergrounding those.”
This story was originally reported and published by WBUR.
