EPA must retain the requirement that rate-based states seeking to engage in interstate trading merge their target emission rates.
EPA’s proposed Clean Power Plan recognizes that by working together, states can more efficiently reduce carbon dioxide (“CO2”) emissions from existing power plants. The proposal allows states to “jointly demonstrate emission performance by [power plants]. States can design their plans to reduce tons of CO2 on a mass basis or reduce the rate at which power plants emit CO2. In the case of a rate-based plan EPA proposed that states “would demonstrate that all affected [power plants] subject to the multi-state plan achieve a weighted average CO2 emissions rate that is consistent, in aggregate, with an aggregation of the state-specific, rate-based CO2 emission guidelines that apply to each of the participating states.” Under a mass-based approach states would add together the tons of CO2 their states must eliminate from their power plants and meet that combined tonnage budget.