	Introduction

On August 3, 2015, the Environmental Protection Agency (EPA) finalized regulations to address carbon dioxide (CO 2 ) emissions—or CO 2 emission rates—at existing electricity generating units (EGUs). EPA estimates that in 2030, the CPP will result in a 32% reduction in CO 2 emissions from the electric power sector in the United States compared to 2005 levels. The CPP is the subject of ongoing litigation in which a number of states and other entities have challenged the rule, while other states and entities have intervened in support of the rule. Opponents of the rule applied to the Supreme Court in late January 2016 for an immediate stay of the CPP final rule. Therefore, the CPP deadlines (discussed below) do not have legal effect and will likely be delayed if the rule is ultimately upheld. CRS Report R44265, EPA's Clean Power Plan: Implications for the Electric Power Sector , by [author name scrubbed]. The final rule requires states to submit to EPA either an initial plan or final plan by September 6, 2016. By comparison, the proposed rule would have allowed states to receive a one-year extension for submitting their final plan and a two-year extension if states submitted a multi-state plan. If a state fails to submit a satisfactory plan by EPA's regulatory deadline, CAA Section 111(d) directs EPA to prescribe a plan for the state, often described as a federal implementation plan (FIP). The final rule establishes uniform national CO 2 emission performance rates (measured in pounds of CO 2 per MWh of electricity generation) for each of the two subcategories of EGUs—fossil-fuel-fired electric steam generating units (e.g., coal, oil, or natural gas units) and stationary combustion turbines (e.g., natural gas combined cycle units)—affected by the rule. These standards are the underpinnings for the state-specific emission rates and mass-based targets. The interim and final targets, however, differ from the ones in the proposed rule. The final rule implies lower percentage reduction requirements for some states and implies higher percentage reduction requirements for others compared to the proposed rule. EPA's Methodology

The methodology (i.e., underlying calculations and assumptions) in the final rule that EPA used to create (1) the national CO 2 emission performance rates and (2) the state-specific emission rate and mass-based targets is considerably different from EPA's methodology in its proposed rule. Building Blocks

Both the final and proposed rules included "building blocks" in the underlying calculations. As a result, some of the states' 2030 mass-based targets are higher than their 2012 emission baselines. However, EPA made several state-specific adjustments in the final rule to address some of the concerns. This program would provide incentives to states to develop renewable energy projects in 2020 and 2021 (discussed below). Nuclear Power Treatment

EPA modified its treatment of nuclear power in the final rule. EPA clarified that the final rule would allow the generation from under-construction units, new nuclear units, and capacity upgrades to help sources meet emission rate or mass-based targets. Biomass Treatment30

In its final rule, EPA would allow states to use "qualified biomass" as a means of meeting state-specific reduction requirements. This appears to be a narrower approach than was taken in the proposed rule. Energy efficiency and solar renewable energy projects in low-income communities, and 2. In particular, the final rule contains a provision for a reliability "safety valve" for individual power plants. The reliability safety valve allows for a 90-day reprieve from carbon emissions limits.
On August 3, 2015, the Environmental Protection Agency (EPA) finalized regulations that address carbon dioxide (CO2) emissions in the electric power sector. The Clean Power Plan (CPP) final rule requires states to submit plans that would reduce carbon dioxide (CO2) emissions or emission rates—measured in pounds of CO2 emissions per megawatt-hour of electricity generation—from existing fossil fuel electricity generating units. EPA estimates that in 2030, the CPP will result in CO2 emission levels from the electric power sector that are 32% below 2005 levels.
The CPP is the subject of ongoing litigation in which a number of states and other entities have challenged the rule. On February 9, 2016, the Supreme Court stayed the CPP for the duration of the litigation. The CPP therefore currently lacks enforceability or legal effect, and if the rule is ultimately upheld, at least some of the deadlines would have to be delayed.
For example, the final rule established a deadline of September 6, 2016, for states to submit to EPA plans to comply with the rule with the option for a two-year extension (September 6, 2018). If a state fails to submit a satisfactory plan by EPA's regulatory deadline, the Clean Air Act directs EPA to prescribe a plan for the state, often described as a federal implementation plan.
Emission reductions are scheduled to begin in 2022, giving the states two additional years (compared to the proposed rule) before their plans must go into effect.
The 2015 final rule's state-specific targets are substantially different from those in the 2014 EPA proposed rule. For example, EPA's final rule establishes uniform national CO2 emission performance rates for each of the two subcategories of electricity generating units—fossil-fuel-fired electric steam generating units (whether coal, oil, or natural gas) and stationary combustion turbines (natural gas combined cycle)—affected by the rule. These standards are the underpinnings for the state-specific emission rate and mass-based targets, which, as a result, are considerably different from the proposed rule.
The final rule's state targets imply lower percentage reductions for some states, while implied percentage reductions are higher for others states compared to the proposed rule. The state-specific targets differ, because EPA altered its methodology (i.e., underlying calculations and assumptions) compared to the proposed rule. For example, EPA eliminated "building block" 4 (energy efficiency improvements) and other "building blocks."
In the final rule, EPA continues to use 2012 data as the baseline for calculated state targets. However, the agency made several state-specific adjustments to address concerns raised by stakeholders.
EPA also modified its treatment of nuclear power in the final rule, removing both "at risk" and under-construction nuclear power from the emission rate calculations. EPA clarified that the final rule would allow the generation from under-construction units, new nuclear units, and capacity upgrades to help states meet their compliance objectives.
EPA would allow states to use "qualified biomass" as a means of meeting state-specific reduction requirements. This appears to be a narrower approach to biomass than in the proposed rule.
The final rule contains a provision for a reliability "safety valve" for individual power plants. This mechanism would allow for a 90-day reprieve from emissions limits in an emergency situation.
In addition, EPA created a new program to encourage states to support renewable energy and energy efficiency projects (in low-income communities) in 2020 and 2021.