Renewable Power for Agriculture Incentive Program Act of 2008 - Amends the Internal Revenue Code to allow a business-related tax credit for excessive fuel costs for creditable fuel (i.e., fossil fuel or electricity) used by a taxpayer in the trade or business of farming. Defines "excessive fuel cost" as the excess amount paid for creditable fuel over the adjusted base price for such fuel (the average price for such fuel on September 6, 2004, for the region in which the taxpayer purchased such fuel). Terminates such credit after 2013.