gas emitting energy generating units over their competitors. (13) States and State commissions should be encouraged to incorporate the cost of greenhouse gas emissions into wholesale rates for electricity. 4. Certain rates unjust, unreasonable, unduly discriminatory, or preferential (a) In general For the purposes of section 205 and section 206 of the Federal Power Act ( 16 U.S.C. 824d , 824e), if the Federal Energy Regulatory Commission determines that a rate for the wholesale sale of electricity does not incorporate the cost of externalized greenhouse gas emissions to public health, safety, or welfare, then the Federal Energy Regulatory Commission shall find that such rate is unjust, unreasonable, unduly discriminatory, or preferential. (b) Greenhouse gas defined In this subsection, the term greenhouse gas includes— (1) any gas identified by the Environmental Protection Agency in the final rule titled Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act published on December 15, 2009 (74 Fed. Reg. 66496), including carbon dioxide, hy­dro­fluo­ro­car­bons, methane, nitrous oxide, per­fluo­ro­car­bons, and sulfur hexafluoride