An attack on the United States' unprotected grid could leave the nation without electricity for months or even years, experts are warning the government.

Because the U.S. and its utility companies have not hardened the 450,000 miles of commercial transmission lines or the critical 2,000 transformers nationwide, a significant attack could black out the grid long term, damaging all the infrastructure Americans rely on to have access to money, food and transportation for months or years, a panel of experts warned the House Oversight and Government Reform Committee Wednesday.

An attack "could black out the national electric grid for months or years and collapse all the other critical infrastructures — communications, transportation, banking and finance, food and water — necessary to sustain modern society and the lives of 310 million Americans," warned panelist Peter Pry, executive director of the Task Force on National and Homeland Security for the Noah Group, a research organization.

A 2008 study on the long-term consequences of an electromagnetic pulse (EMP) attack found the U.S. so dependent upon electricity to access food, clean water and transportation that it concluded that if the U.S. was hit by a large-scale EMP attack, within 12 months of a nationwide blackout the after-effects would kill "nine of 10 Americans through starvation, disease and societal collapse."

Last summer, al Qaeda succeeded in a terrifying "first ever" for national security planners: Using rockets and mortars, the terrorist group took out Yemen's entire electric grid by destroying key transmission towers.

Almost a year later, most of the country, now overtaken by Houthi rebels and just this week getting respite from a Saudi-led aerial bombing campaign, still suffers from a lack of electricity, affecting residents' access to food, medical care, money and transportation.

What maddens the experts is that the fixes that would greatly improve the United States' resistance to an attack on the grid — whether from a kinetic attack, a natural disaster or an EMP attack — aren't that expensive in relation to the amount of money spent on other types of national defense. It would cost only about $30 billion to upgrade the whole thing, said George Baker, a professor at James Madison University in Harrisonburg, Va., who testified before the committee.

"We have the engineering know-how and tools to protect ourselves," Baker said. "What is lacking is the resolve."

If $30 billion is too large of a price tag, Baker told the Washington Examiner he would start with about $1.5 billion — the amount he says it would take to put electromagnetic shielding and the equivalent of high-end surge protectors on all incoming power and communications lines to key transformers throughout the country.

A hit to just a few of those transformers at once could affect power access to millions of people for months, Baker said. The U.S. has no way to replace them other than to order them from the two countries that produce them – Germany and South Korea. A replacement takes 18 months to produce.

A more comprehensive defense, which he estimates would cost $30 billion, would include protecting the power sources the grid relies on to run, such as its access to natural gas and the transportation networks that carry that fuel to power plants.

Baker said the problem has been long-deferred because to admit the vulnerability might expose the power companies to liability if they are hit.