Nationwide average prices for alternative fuels and conventional fuels vary from state to state. With biodiesel fuels, a lot depends on the concentration of the mix; the higher the mix of biodiesel to regular petroleum diesel, the higher the price at the pump.

In April of 2009, The United States Department of Energy reported that biodiesel with a B20 rating was approximately 22 cents a gallon more than regular diesel, and biodiesel with a B99/B100 blend was approximately a dollar higher. For the purpose of this report, prices for conventional and alternative fuels were collected from a cross section of fuel providers, stakeholders and Clean City Coordinators. Major fuels such as propane, natural gas, ethanol, as well as biodiesel fuels were compared to conventional fuels such as diesel and petroleum. Prices from private and public gas and refueling stations around the country were collected over a two week period and then averaged to give an overall regional price. Prices included any sales prices as well as retail prices, including any motor fuel taxes.

Biodiesel fuel is also cost effective when adhering to federal regulations. An Act implemented in 1998 now permits state, federal and alternative fuel providers who comply with EPAct (Energy Policy Act) to match up to 50 percent of their alternative fuel based light duty vehicles purchased with biodiesel. This opens up the option in vehicles above 8,500 pounds to use 450 gallons of biodiesel. The stipulation is that 450 gallons of biodiesel must be purchased and used in a 20% minimum blend.

As with other regular petroleum diesels, the cost of biodiesel fuels depends largely on outside sources such as the vegetable oil market. A biodiesel of a 20 percent blend with regular petroleum diesel can cost approximately 20 cents more per gallon than regular petroleum diesel alone. In a recent study it was found that a fleet using a 20% blend would have reduced annual costs when compared to other alternative and regular fuels.

At the start of June 2010, prices for biodiesel fuels rocketed by more than 22% due to a congressional failure in renewing a tax credit that has enabled a lot of biodiesel producers to stay in business. In some areas, prices rose from $3.89 to $4.75, causing concern for businesses and consumers alike. With the tax incentive not being passed, biodiesel is not so competitive when compared to regular petroleum diesel. At the beginning of August 2010, the biodiesel market took yet another beating. Prices once again rose sharply due to a temporary ban in Russia on grain exports. This ban had a knock-on effect with the corn and soybean markets, both of which are a major part of the biodiesel production. In general, the cost comparisons between biodiesel fuel and regular fuel are varied. The costs are dependent upon many factors which are subject to change from day to day, and the decision on whether or not to purchase biofuel rather than regular fuel will depend on the reasons for wanting to use a biofuel in the first place.