Gasoline prices in the United States heading into Thanksgiving are the lowest in five years and should continue to drop, the Energy Department said Wednesday.

The average retail price for a gallon of regular unleaded gasoline in the United States is $2.81, according to motor club AAA, which is nearly 50 cents lower than one year ago and the lowest average price heading into the Thanksgiving holiday season since 2009.

The Energy Information Administration, the analytical arm of the Energy Department, said the decline in gasoline prices is largely a reflection of crude oil prices, which have shed more than 20 percent of their value since June. Gasoline prices are down more than 88 cents per gallon since the start of July, EIA said.

EIA said it expects gasoline prices to keep falling for the rest of the year, barring any major catastrophe, to settle at $2.80 for a monthly average in December.

Last year's annual average price was $3.51 per gallon and EIA said it expects an average $3.39 per gallon for 2014. For full-year 2015, the average price for a gallon of regular unleaded should be $2.94 per gallon.

Retailers and market analysts say low prices at the pump should give U.S. consumers more disposable income during the holiday season, though holiday travelers will still spend most of their money on fuel.

AAA estimates more than 41 million people will drive more than 50 miles from home for the Thanksgiving holiday, which runs officially from Wednesday through Sunday. If its forecast is accurate, it would mark the busiest Thanksgiving on the road in seven years.