During the Gibson interview:

Let me speak specifically about a credential that I do bring to this table, Charlie, and that’s with the energy independence that I’ve been working on for these years as the governor of this state that produces nearly 20 percent of the U.S. domestic supply of energy, that I worked on as chairman of the Alaska Oil and Gas Conservation Commission, overseeing the oil and gas development in our state to produce more for the United States.

Factcheck.org says it’s "not even close":

It’s simply untrue that Alaska produces anything close to 20 percent of the U.S. "energy supply," a term that is generally defined as energy consumed. That category includes power produced in the U.S. by nuclear, coal, hydroelectric dams and other means – as well as all the oil imported into the country.

Palin would have been correct to say that Alaska produces just over 14 percent of all the oil produced in the U.S., leaving out imports and leaving out other forms of power. According to the federal government’s Energy Information Administration, Alaskan wells produced 263.6 million barrels of oil in 2007, or 14.3 percent of the total U.S. production of 1.8 billion barrels.

But Alaskan production accounts for only 4.8 percent of all the crude oil and petroleum products supplied to the U.S. in 2007, counting both domestic production and imports from other nations. According to EIA, the total supply was just over 5.5 billion barrels in 2007.

Furthermore, Palin said "energy," not "oil," so she was actually much further off the mark. According to EIA, Alaska actually produced 2,417.1 trillion BTUs [British Thermal Units] of energy in 2005, the last year for which full state numbers are available. That’s equal to just 3.5 percent of the country’s domestic energy production.

And according to EIA analyst Paul Hess, that would calculate to only "2.4 percent of the 100,368.6 trillion BTUs the U.S. consumes."

Now the kicker – this Washington Post follow-up:

After nonpartisan Factcheck.org pointed out Palin’s error in her interview with Gibson, the governor revised her statement somewhat, limiting it to oil and gas. But data compiled by the Energy Information Administration (EIA) contradict her claim that she oversees "nearly 20 percent" of oil and gas production in the country. According to authoritative EIA data, Alaska accounted for 7.4 percent of total U.S. oil and gas production in 2005. It is not even correct for Palin to claim that her state is responsible for "nearly 20 percent" of U.S. oil production. Oil production has fallen sharply in Alaska during her governorship. The state’s share of total U.S. oil production fell from 18 percent in 2005 to 13 percent this year, according to the EIA.