And on the third day, with trees still dangling and temperatures still sweltering and hundreds of thousands still without power, it was time to discuss going underground.

Not descending into basements or caves, mind you, but burying the power lines.

The prolonged recovery from Friday’s destructive storm has rekindled questions about why much of the region’s electric infrastructure remains above ground, exposed to the vagaries of the weather, and whether the necessary money and political wherewithal can be mustered to bury more power lines.

D.C. Mayor Vincent C. Gray (D) was one of several public officials to call Monday for new consideration of “undergrounding,” as the utility industry calls it. “People are fed up with power outages,” he said. “We need a game-changer.”

Changing the game, experts agree, would be somewhere between moderately and astoundingly expensive and might create nearly as many reliability issues as it solves. Yet many jurisdictions nationwide mandate underground infrastructure for new construction. A few others have undertaken ambitious efforts to bury existing overhead lines.

In the Washington area, efforts to bury power lines have been abortive, snarled not only by the tremendous cost, but also by political and regulatory complications. Pepco this year has proposed burying a pair of its most troublesome D.C. “feeders” — distribution lines that reach into neighborhoods — but first the District’s Public Service Commission must rule on the utility’s method for choosing which feeders to bury.

Whether to bury more of the region’s electric power infrastructure is not a new question. The D.C. commission has been exploring the potential of undergrounding since 2003; it commissioned an independent study of the feasibility and benefits, and Shaw Consultants International delivered the report two years ago.

The consultants analyzed three major options: burying virtually all power lines, burying only major distribution lines, and undergrounding both distribution lines and neighborhood feeders.

For $1.1 billion, the study found, primary distribution lines could be buried, eliminating 65 percent of customer outages related to overhead lines. At about double that cost, primary and secondary lines could be placed underground, cutting 87 percent of overhead outages. Burying all overhead lines, including household service lines, would cost $5.8 billion and could prevent more than 1,000 annual outage incidents.

Michael W. Maxwell, Pepco’s vice president for asset management, said the company ran the numbers last year: Spread out among all of the utility’s residential customers in the District over 10 years, a full undergrounding would add $226 to the average monthly bill. Spread over 30 years, that figure would drop to $107.

“This is an expensive proposition,” Maxwell said. “And we are a business, and there is a regulatory process in place around cost recovery. The commission has to say this is or is not prudent.”

The cost challenges are even greater in Maryland, the remainder of Pepco’s territory. In the District, nearly 80 percent of Pepco’s high-voltage lines are buried. In Maryland, only 57 percent of Pepco’s 8,400 miles of those lines are buried.

New construction projects in Maryland must include underground electrical work, unless utility poles are already present. In 2005, the Maryland Public Service Commission studied whether creating a statewide system of underground lines would be wise. The group concluded that building such a system would be too expensive, but PSC Chairman Douglas R.M. Nazarian said in a conference call Monday that Pepco and the state are looking to see whether there are specific areas in the Washington region where lines could be buried. Maxwell said Monday that Pepco is exploring projects along Randolph Road in Montgomery County and Crain Highway in Prince George’s County.

Montgomery County Executive Isiah Leggett (D) said in a news conference Monday that he’d be open to putting some utility lines in the county underground but that a countywide effort could cost $3 billion to $4 billion. He said the county is trying to figure out in which areas such utility work would be most cost-effective.

The D.C. consultants concluded that burying only primary distribution lines and troublesome secondary lines offered the most bang per buck, and Maxwell said that is what Pepco has embarked on.

Pepco approached the commission this spring about burying two of its most problematic feeders — one, on a stretch of Oregon Avenue NW bordering Rock Creek Park, the other on Michigan Avenue NE near Catholic University. First the commission will rule on whether the utility is justified in choosing those particular lines; the cost of replacing them is bound up in a pending rate-increase case — part of which includes the possibility of a surcharge for capital improvements.

People’s Counsel Sandra Mattavous-Frye, a government advocate for utility ratepayers, said the commission has been reluctant to order additional undergrounding. Pepco is “not going to do anything until the commission directs them to do something,” she said.

Mattavous-Frye said that since the storm, residents have called her office asking why more lines haven’t been buried. “Consumers are saying, ‘Why not? What’s the problem? Hasn’t the case been made?’ ”

The case for undergrounding has been complicated by the fact that the reliability benefits of burying lines is offset by the higher cost and the difficulty of maintaining those lines.

A 2009 report from the Edison Electric Institute, a trade association for public utilities, said data show that underground systems have “only a slightly better reliability performance” than above-ground systems.

Pepco said in a 2008 report that outages involving overhead wires took 2.8 hours to repair, while the average outage involving underground equipment took 4.4 hours. But during and after storm events, the calculation changed: Above-ground equipment took an average of 8.2 hours to repair, “while there were no [underground] storm related failures for comparison.”

Nikita Stewart and Victor Zapana contributed to this report.