For the planning year June 1, 2011, through May 31, 2012, the IPA Act requires that RECs equivalent to 6% of Ameren Illinois Company's eligible retail customer load for June 1, 2009 through May 31, 2010 be acquired through this RFP. Eligible retail customers include those residential and non-residential customers with peak demands less than 400 kW who acquire power and energy under fixed price tariffs. Based on the Reference Year Delivered Volume of 15,869,084 MWh and the 6% minimum RPS requirement, the target quantity to be procured is 952,145 RECs. Each REC represents the environmental attribute corresponding to one megawatt-hour (1 MWh) of energy produced from renewable energy resources that qualify under the IPA Act.

Notwithstanding these goals, lesser quantities than the quantities stated above may be purchased if the RECs are deemed to be not "cost effective" in accordance with the IPA Act. (Section 1-75(c)(1) - (2).) The amount of renewable purchases shall be limited such that the estimated average net increase due to the cost of the RECs included in the amounts paid by eligible retail customers is the greater of an additional 0.5% of the amount paid for electric service by those customers during the year ending May 31, 2010, or 2.0% of the amount paid per kWh by those customers during the year ending May 31, 2007. The Renewable Energy Resource Budget ("RRB") for the 2010-2011 delivery period for Ameren Illinois Company is therefore $30,180,309. REC purchases that cause this budget to be exceeded are deemed to be not "cost effective."