U.S. retail gas prices dropped 15 cents a gallon in the past two weeks, the sharpest decline in nearly a year, according to a survey released Sunday in Camarillo.

The national average for self-serve regular stood at $2.87, down from just under $3.03, according to the Lundberg Survey of 7,000 gas stations across the country. That was about 25 cents higher than prices at the same time in 2005.

Midgrade prices averaged $2.98 a gallon, while premium cost $3.09.

The lowest price was $2.60 a gallon in Des Moines, Iowa, and the highest was in Honolulu at $3.32.