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Expert Forum on EPA’s Clean Power Plan

By Jennifer Macedonia

Tuesday, October 21, 2014

Earlier this fall, Resources for the Future invited a slew of experts to comment on questions related to the administration’s Clean Power Plan, including who (and how) should translate the states’ assigned rate-based goals into mass-based goals?

Jennifer Macedonia, senior advisor to BPC, contributed a post and highlighted “three thorny aspects” to converting from rate-based goals into mass-based. She analyzes them and concludes that the U.S. Environmental Protection Agency should clarify the methodology for conversion and the result of applying such methodologies, subject to a public notice and comment period.

Read her post below.


The translation of a rate-based state goal into a mass-based state goal is intended to produce an equivalent value. However, depending on which assumptions and methodology are applied, a variety of outcomes is possible. These potential differences impact the stringency of what is required within each state to implement Section 111(d). If the stringency can vary based on available methodological choices, is there truly an “equivalent” value?

Although conceptually simple—Emission Rate (lbs/MWh) * Generation (MWh) = Mass Emissions (tons)—there are at least three thorny aspects to the translation from rate to mass in practice.

  1. Future generation is unknown. Like equating speed and distance when time is undefined, converting an emissions rate to an equivalent mass of emissions for a future year is challenging because the amount of future electricity generation is unknown.
  2. Measures that will be enforceable under the state plan are to be excluded from the projection scenario. EPA proposes the use of a projected scenario to convert from rate- to mass-based goals and proposes that any programs that will be enforceable under the state plan should be excluded from the scenario. This sets up a decisionmaking loop, where the goal conversion is dependent on decisions to be made in developing a state plan to implement the goal.
  3. The state goal is not an emissions rate. The conversion is further complicated because the state goal is not in the form of a simple emissions rate. In setting up a mechanism to credit what is, in essence, a mass-based quantity (the CO2 emissions avoided through various actions that offset generation and emissions from affected fossil-fired generators), EPA created a new metric for state goals (see discussion here). This quasi-emissions rate includes adjustments to account for CO2 avoidance from renewable energy, a portion of nuclear energy, and end-use energy efficiency measures.

The quasi-emissions rate means it is not mathematically correct to simply multiply the rate times generation to get mass emissions, as suggested in the equation above. This adds another twist to an already challenging problem of determining the appropriate generation for converting the rate-based goal to a mass-based goal.

Such uncertainty has the potential to create confusion, lead to delays, and produce inequalities across states. Given the tight timing, the importance of state-specific analysis to develop an implementation plan that meets state objectives, and the time required for potential collaboration with stakeholders, legislatures, and other states, it would be detrimental to find out years into that effort that EPA did not find the translation to a mass-based goal approvable.

States and stakeholders would benefit from upfront clarity regarding an acceptable methodology and assumptions, as well as an opportunity to comment on the proposed conversion in a transparent way and before all of the detailed work is done to analyze, negotiate, and develop a plan. Thus, it would be beneficial for EPA to clarify both (a) the proposed methodology for converting from rate- to mass-based goals and (b) the result of applying the methodology to calculate mass-based state goals, subject to a public notice and comment period.

KEYWORDS: 111(D) REGULATIONS, CLEAN AIR ACT, ENVIRONMENTAL PROTECTION AGENCY