Expect the cost of on-highway diesel to average $3.81 per gallon this year, 11 cents less than 2013’s average price. The new monthly U.S. Energy Department Short-Term Energy Outlook is calling for the price to be even less in 2015, averaging $3.72 per gallon.

Regular grade gasoline prices are also projected to move lower, averaging $3.46 per gallon this year, after averaging $3.51 last year and $3.63 in 2012.

The reason is oil prices are projected to move lower, with West Texas Intermediate Crude expected to average $93 per barrel this year, after averaging close to $98 dollars last year, then falling below $90 in 2015. Prices for North Sea Brent Crude are also expected to move lower.

The decline in diesel prices is also expected to come as demand for U.S. diesel exports is expected to grow stronger, but increasing oil production domestically and abroad should help avoid any price hikes.

U.S. crude production is forecast to average 7.5 million barrels per day in 2014, an increase of 1 million barrels per day from 2013. It’s expected to move even higher in 2015, hitting 9.3 million barrels per day, which would make the highest annual production level since 1972.

Also non-member countries of the OPEC oil cartel are forecast to increase their oil production to a record high of 1.9 million barrels per day in 2014, while OPEC member nations are expected to reduce production slightly. The end result should be an increased surplus of crude on a worldwide basis.

The one energy price increase that is expected is in the area of natural gas, which is projected to increase from an average of $3.73 “Henry Hub” per million British thermal units last year, to $3.89 this year and $4.11 in 2015. End user prices can vary greatly between different uses. Natural gas is expected to see record U.S. consumption once 2013 final numbers are in, according to DOE.

The full report is available online.