While underground wires appear less vulnerable than aboveground power lines, they have several disadvantages. Aboveground lines are typically uninsulated and cooled by air. Underground lines, in contrast, quickly build up heat.

One way to prevent underground cables from melting is to bathe them in oil traveling inside the same steel piping. That oil must be constantly cleaned to maintain its cooling properties as well as to keep it from breaking down into hydrogen gas, which can be explosive, said Stan Johnson, a manager at the North American Electric Reliability Council, a federal watchdog agency in Princeton, N.J.

An alternative is to cool underground lines by letting a certain amount of electricity "bleed through" to the ground, Potter said. That has the disadvantage of making them less efficient, and the resulting electrified ground can harm animals or humans.

Underground wires are also more vulnerable to being accidentally dug up, especially during "backhoe mating season," said Peak 10's Biggs.

Repairing underground wires also takes longer. And they are not necessarily less prone to storm damage, said NERC's Johnson, who pointed out that salt water brought in by hurricanes can cause as much damage to underground lines as winds do to the overhead variety.