NORTHBRIDGE

PRELIMINARY

Translating Rate-Based Goals to Mass-Based Goals:

EPA’s GDC Methodology with Load Growth

October 17, 2014
NORTHBRIDGE

PRELIMINARY

INTRODUCTION

These materials review an approach to translating rate-based into mass-based goals that builds on 

EPA’s goal data computation (GDC) methodology and load growth expectations.

The methodology is intended to:

1. Be a simple and transparent method for quickly providing provisional mass goals to states 

and allowing those goals to be updated for state challenges or other EPA modifications. 

2. Preserve the environmental integrity of the rule while facilitating state choice of mass goals. 

3. Be fully consistent with EPA’s definition of BSER and GDC process

• The GDC process calculates emission rate goals using assumptions for each of the 4 

BSER building blocks

• This translation methodology uses the same GDC process, calculations and 

assumptions to estimate mass goals 

• Because it relies on the same process, calculations and assumptions, the mass goals 

resulting from this methodology are equivalent to the emission rate goals.

These materials:

 Review a translation methodology that covers both existing and new sources

 Benchmark the national results to IPM and other data

 Compare state-by-state emission goal results 

 Discuss issues related to restricting the mass goal to existing sources 

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NORTHBRIDGE

PRELIMINARY

METHODOLOGY Illustrative U.S. Calculation

Illustrative 2030 Mass-Based Calculation for Existing and New Sources (Total U.S.) *

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

2012 Retail

Sales, Plus

1.0751x Grossup (From GDC)

+ 0.84%

Average

Annual Load

Growth

2030 Retail

Sales, Plus

1.0751x Grossup (BAU)

2030 EE

Potential

(BB 4)

2030 Total

MWh Net of EE

2030 Total

Renewables

(BB 3)

Nuc.,

Uncovered

Res., Net Imp.,

& Other Gen. at

2012 Levels

Demand for

Covered Fossil

Generation

(Existing &

New)

NGCC (E/U)

Redispatched

up to 70% CF

(BB 2)

Redispatched

Coal and O/G

Steam

Coal O/G Steam NGCC Other Covered 111(d) Nuclear + Uncovered 111(d) + Net Imports/(Exports) Renewables Energy Efficiency

Energy Efficiency and Renewable 

Energy (BB 3 & 4) are deployed 

per GDC

Nuclear, uncovered and 

net imports are assumed 

to remain at 2012 levels

The residual 

demand is left for 

fossil generation to 

meet in each state In each state, NGCC 

runs up to a 70% 

capacity factor, with 

coal and oil/gas 

steam providing the 

last increment of 

generation

TWH

2012 state retail sales grow 

at the regional rate imbedded 

in the 2030 BAU IPM run

(similar to NOx SIP call)

2

* Note: This is an illustration of calculations that 

are performed on a state-by-state basis. 
NORTHBRIDGE

PRELIMINARY

METHODOLOGY National Results

Summing the state-specific mass goals implies a national mass goal (for both existing and 

new sources) that is 19% below 2012 levels.

U.S. Generation Mix by Source

1474 1044

100

33

959

1402

80 80

1123 1123

218 523

381

0

1,000

2,000

3,000

4,000

5,000

2012 2030 Results

(Existing & New)

TWH

Energy Efficiency

Renewables

Nuclear + Uncovered 

Sources + Net 

Imports/(Exports)

Other Covered 

Generation

NGCC

O/G Steam

Coal

1480

982

66

23

377

548

29

29

1,953

1,582

0

500

1,000

1,500

2,000

2,500

2012 2030 Results

(Existing & New)

Covered Emissions 

(MM tonnes)

19% Reduction in 

Covered Emissions

U.S. Covered Emissions by Source

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PRELIMINARY

BENCHMARK U.S. RESULTS

With IPM derived load growth, sector emissions are very close to the Option 1 State case.

1,953

2,139

1,600 1,582

2,381

2,039

2,256

1,701 1,669

0

500

1,000

1,500

2,000

2,500

2005 (EIA) 2012 (EIA,

EPA G.D.C.)

2030 (EPA

R.I.A. BAU)

2030 (EPA

Option 1 State)

2030 (MassBased)

Million Metric Tonnes

U.S. Electric Sector Emissions: Historical and Projected

Note: EPA data from Regulatory Impact Analysis (R.I.A.). Covered sources are approximated by 

emissions totals from all units >25 MW excluding Indian Country units. 

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Uncovered Sources

Covered Sources

(Existing & New)
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STATE-BY-STATE RESULTS GDC/LG compared to Rate

Percent Change in Emissions and Emission Rates Relative to 2012 Levels

(2012 Covered Emissions = 100)

Note: Mass-based goal data is a comparison to 2012 on a tonnage basis, while the rate-based goal is a comparison to 2012 on a rate basis.

2012 

Actual 

= 100

0

20

40

60

80

100

120

140

160

CT

MA

ME

NH

NY

RI

AL

AR

AZ

CO

DE

FL

GA

IA

IL

IN

KS

LA

MD

MI

MN

MO

MS

MT

NC

ND

NE

NJ

NM

NV

OH

OK

OR

PA

SC

TX

UT

VA

WA

WI

WV

WY

CA

ID

KY

SD

TN

2012 Covered Emissions

2030 Mass-Based Spreadsheet Emissions vs 2012 Covered Emissions

2030 Rate-Based Goal vs 2012 Covered Emissions Rate

States with mass-based reductions 

exceeding rate-based reductions due 

to low load growth and little/no coal 

“Typical” States:

Mass-based reduction is between 

2012 levels and rate-based reduction

States with mass-based goal above 

2012 levels due to load growth and 

limited abatement options

For most states, the percentage reduction in tonnes under a mass-based goal would be less 

than the percentage reduction in rate-based goals.

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NORTHBRIDGE

PRELIMINARY

STATE-BY-STATE RESULTS GDC/LG compared to IPM

Percent Change in Emissions Relative to 2012 Levels

(2012 Covered Emissions = 100)

States with mass-based reductions 

exceeding rate-based reductions due 

to low load growth and little/no coal 

“Typical” States:

Mass-based reduction is between 

2012 levels and rate-based reduction

States with mass-based goal above 

2012 levels due to load growth and 

limited abatement options

The variability of mass-based goals, on a percentage basis, is lower under this method than 

under IPM; reducing it further would require modifications to the underlying GDC process.

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0

20

40

60

80

100

120

140

160

CT

MA

ME

NH

NY

RI

AL

AR

AZ

CO

DE

FL

GA

IA

IL

IN

KS

LA

MD

MI

MN

MO

MS

MT

NC

ND

NE

NJ

NM

NV

OH

OK

OR

PA

SC

TX

UT

VA

WA

WI

WV

WY

CA

ID

KY

SD

TN

2012 Covered Emissions

2030 Mass-Based Spreadsheet Emissions vs 2012 Covered Emissions

2030 Opt1-State (IPM Modeled Policy) vs 2012 Covered Emissions

2012 

Actual 

= 100
NORTHBRIDGE

PRELIMINARY

STATE-BY-STATE RESULTS GDC/LG compared to IPM

Absolute Change in Emissions Relative to 2012 Levels

The variability of mass-based goals, on an absolute basis, is lower under this method than 

under IPM. Allowing states to choose between methods affects overall reductions.

8

States with mass-based reductions 

exceeding rate-based reductions due 

to low load growth and little/no coal 

“Typical” States:

Mass-based reduction is between 

2012 levels and rate-based reduction

States with mass-based goal above 

2012 levels due to load growth and 

limited abatement options

CO2 Emissions Reductions, Relative to 

2012 Levels (MMmtCO2)

(100)

(80)

(60)

(40)

(20)

0

20

40

60

CT

MA

ME

NH

NY

RI

AL

AR

AZ

CO

DE

FL

GA

IA

IL

IN

KS

LA

MD

MI

MN

MO

MS

MT

NC

ND

NE

NJ

NM

NV

OH

OK

OR

PA

SC

TX

UT

VA

WA

WI

WV

WY

CA

ID

KY

SD

TN

2030 Mass-Based Spreadsheet Emissions vs 2012 Covered Emissions

2030 Opt1-State (IPM Modeled Policy) vs 2012 Covered Emissions

% 

Reduction 

from 2012

% 

Reduction 

from 2005

States w/ 

Higher

Emissions 

IPM 17% 29% 25

GDC/LG 18% 30% 22

Higher of 2 12% 25%
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 -

 50

 100

 150

 200

 250

TX

OH

FL

PA

IN

IL

KY

GA

WV

AL

MO

MI

NC

NYTN

AZ

OK

WI

WY

LA

CA

VA

CO

SC

KS

UT

MN

IA

MD

NM

ND

NV

AR

MS

MA

NE

NJ

MT

WA

CT

OR

NH

ME

SD

RI

DE

ID

DC

VT

CO2 (MMmtCO2)

Mass-based CO2 Emission Targets by State

Increase from

2005 to 2012

STATE-BY-STATE RESULTS GDC/LG compared to 2005

2005 Historic Level

2012 Historic Level

Target: IPM Modeling Results, Option1-State Scenario

Target: Mass-Based Spreadsheet Calculation

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