B.__No less than the following percentages of its portfolio of supply sources for retail electricity sales in this State are accounted for by tier 2 renewable resources:

(1) Between September 1, 2005 and August 31, 2006, 2%;

(2) Between September 1, 2006 and August 31, 2007, 2.5%;

(3) Between September 1, 2007 and August 31, 2008, 3%;

(4) Between September 1, 2008 and August 31, 2009, 3.5%;

(5) Between September 1, 2009 and August 31, 2010, 4%;

(6) Between September 1, 2010 and August 31, 2011, 4.5%;

(7) Between September 1, 2011 and August 31, 2012, 5%;

(8) Between September 1, 2012 and August 31, 2013, 5.5%;

(9) Between September 1, 2013 and August 31, 2014, 6%;

(10) Between September 1, 2014 and August 31, 2015, 6.5%; and

(11) After Augusta 31, 2015, 7%.

This requirement is referred to in this section as "the Tier 2 Requirement."

If a competitive electricity provider represents to a customer that the provider is selling to the customer a portfolio of supply sources that exceeds the Tier 1 Requirement or the Tier 2 Requirement, the resources necessary to supply that excess may not be applied to meet the aggregate Tier 1 Requirement or aggregate Tier 2 Requirement.

The commission shall allow competitive electricity providers to satisfy the requirements of this subsection through the use of renewable credits if the commission determines that a reliable system of trading exists for such credits.

Rules adopted under this subsection are major substantive rules pursuant to Title 5, chapter 375, subchapter 2-A.