Burying most power lines underground in New Hampshire would cost $43 billion and take more than 40 years to complete, according to one industry estimate.

That would average out to $68,313 for each Public Service of New Hampshire customer, according to a 2009 report assessing the historic 2008 ice storm.

“It’s hard to envision getting an economic case to bury all the power lines in the state,” Tom Frantz, director of the electric division of the state Public Utilities Commission, which regulates electric companies, said Friday.

Last weekend’s record-setting snowstorm plunged more than 300,000 Granite State homes and businesses into the dark, with fewer than 200 customers still without power early Saturday.

Mike Carter, associate professor of electrical and computer engineering at the University of New Hampshire, questioned whether utilities here “perhaps are not as aggressive as they could be” with trimming trees before storms strike.

PSNH spokesman Martin Murray blamed Mother Nature — not tree trimming — as the culprit. “The focus of this storm wasn’t on the trees that ought to have been trimmed,” Murray said. “This impact was a result of trees and limbs outside the standard trim zone that came down because of the freakish nature of this storm.”

Frantz said the PUC over the past three to five years approved increases in the tree-trimming budgets of utilities, calling the preventative trimming “a lot of bang for the buck.”

“Tree-related outages are a major cause for outages in New Hampshire,” he said.

Murray said PSNH spent $14 million on tree-trimming in both 2010 and 2011. “We trim more than 2,500 miles of distribution lines per year,” he wrote in an email “To date in 2011, we had trimmed more than 2,000 miles.”

PSNH, the state’s largest electric utility, has sustained four of its five largest outages since December 2008: from an ice storm, a tropical storm, a wind storm and a snowstorm.

“Smart meters”

Meanwhile, the New Hampshire Electric Co-op has installed about a quarter of 81,000 expected “smart meters” in homes and businesses and is working on a “smart grid,” according to Dena DeLucca, vice president of corporate and member services.

Federal stimulus funds totaling $15.8 million will cover 45 percent of the project costs.

“We’ll know immediately when a meter stops receiving power,” she said. “At this point, we only know when people call in and tell us their power is out unless a substation goes out.”

The system could start operating in some areas as soon as June 2012, with all meters fully deployed by November 2012. A customer using an average amount of electricity is paying $4.15 per month for the new technology over about six years. The stimulus funds reduced the cost nearly in half and shortened the timetable by two to three years, DeLucca said.

The new meters will provide the utility with more specific information faster, she said.

After wide-scale electricity outages, people question why utilities don’t bury above-ground power lines. The PUC hired a consultant, NEI Electric Power Engineering of Arvada, Colo., to study the matter. Its 401-page report calculated the cost of putting power lines underground for each utility.

The average cost per customer was $72,563 for the New Hampshire Electric Co-op, $69,140 for Unitil, $68,313 for PSNH and $34,746 for National Grid.

“Due to the increased cost and complexity of retrofitting an overhead system to become an underground system, it is less reasonable to consider underground construction in an existing situation,” the report said.

The report said for an event such as that 2008 ice storm, “any part of the system that was placed underground would have been impervious to the types of damage seen.”

But in this latest storm, PSNH needed to repair underground lines. Last Sunday, “the Manchester underground system experienced a failure, causing an outage to much of the downtown area (including Verizon arena),” Murray said in an email. “The fact that it was underground made it a bit more challenging to locate the exact cause and the location of the outage — and to make the repair.”

In a separate report, the Edison Electric Institute, a Washington association of shareholder-owned electric companies, said “underground lines are not prone to many of the typical overhead outage causes,” such as fallen trees, but can develop problems from flooding and damage to cables from uprooted trees.

The December 2009 EEI report said “the most significant obstacle” to converting lines to underground remains the cost — at five to 10 times the price tag of overhead lines.

Murray pointed out that underground lines, which make up about 7 percent of the utility’s total distribution lines, are connected to existing overhead lines.

Housing developers have the right to choose an underground power feed, he said. “The additional expense is borne by the developer and is then built into the cost of the homes,” Murray said.

Officials don’t know how much the Snowtober snowstorm will cost.

According to the NEI report, reported losses from the 2008 ice storm totaled nearly $155.3 million. That included costs from utilities, state and federal governments and some business losses. The true costs might not be known due to the widespread damage and loss of business and employment opportunities during the holiday shopping season, the report said.

In another section, the report said: “If other economic factors were known such as loss of income, revenue, and profit due to disruptions of electric power, the total economic impact to the state would be much higher.”

Utilities' response to storm faces review