Description of 2012 Unit-level Data Using the eGRID Methodology

The unit-level emissions and generation data derived using the eGRID methodology was relied upon for 

determining state-level totals ultimately used in the goal calculation. One notable difference is that 

published editions of eGRID match emissions and generation at the plant level, while the development of 

the state-level data matches emissions and generation at the unit level in order to filter out units that are 

not likely subject to the Rule’s applicability criteria. Also, the state-level data for goal setting were 

limited to the following elements at the unit level: CO2 emissions, nameplate capacity, net generation, 

state location, and information used to place the unit in each category. The data sources are from reports 

from units that submit data to the EPA under 40 CFR Part 75, and Energy Information Administration 

data from forms EIA-860 and EIA-923. The data were assembled at the unit level and were aggregated to 

the state-level generation totals, capacity totals, and emission rates for the following categories: coal 

steam, Oil Gas Steam (O/G steam), Natural Gas Combined Cycle (NGCC) and Simply Cycle Combustion 

Turbines (CTs), and Integrated Gasification Combined Cycle (IGCC). The year 2012 historical values for 

these categories were then modified for each state to derive the state goal emission rates as described in 

the main body of the Goal Computation TSD.

Industrial units that are not grid connected are excluded. Units for which fossil fuel was less than 10% of 

the heat input in year 2012 were also excluded.

For units that report to the EPA under 40 CFR Part 75, reported CO2 emissions were used. These 

emissions are either determined from continuous emissions monitors that measure CO2 concentration and 

stack gas volumetric flow or, for units that combust certain gaseous and liquid fuels, fuel flow meters and 

fuel testing as required under appendix D and E of 40 CFR Part 75. 

For units that do not report to the EPA under 40 CFR Part 75, CO2 emissions are calculated from fuel use 

reported in the EIA-923 and emission factors under EPA’s Inventory of U.S. Greenhouse Gas Emissions 

and Sinks or The Climate Registry Default Emission Factors. If no unit level fuel use exists in the EIA923 dataset and prime mover fuel data exists, and there is more than one unit at a plant that has the same 

prime mover (e.g. steam turbine, combustion turbine, etc.), then prime mover fuel level emissions are 

distributed to each generator in the prime mover proportionally by nameplate capacity. For most cases 

(where all units in the prime mover would likely be covered by the rule), this apportionment does not 

matter because emissions are summed to the state level. However, if there is a smaller unit in the prime 

mover that would not likely be covered by the rule, then this apportionment may not exactly match the 

amount of fuel actually burned and the associated emissions for each unit. Fuels categorized as “other” 

that could not be defined and assigned an emissions factor were excluded from this task.

Net generation is taken from EIA-923 data. If no unit-level net generation exists in the EIA-923 dataset 

and prime mover fuel data exists, and there are more than one unit at a plant that have the same prime 

mover (e.g. steam turbine, combustion turbine, etc.), then prime mover fuel level net generation is 

distributed to each generator in the prime mover proportionally by nameplate capacity. 

Logic for determination of source CATEGORY:
CATEGORY Category Name Includes

COALST Coal Steam

Coal is designated as primary fuel. Nameplate capacity 25 

MW or greater or if heat input capacity is 250MMBtu/hr 

or greater

OGST Oil Gas Steam

All steam units not in “Coal Steam” category that have oil 

or gas primary fuel. Nameplate capacity 25 MW or 

greater.

NGCC

Natural Gas Combined Cycle Units -Duct 

burners and heat recovery steam generators 

are included with combustion turbines that 

are 25 MW.

NG is primary fuel or if actual fuel use is >90% NG. 

Combustion turbine parts having nameplate capacity 25 

MW or greater. Any associated duct burners and heat 

recovery steam generators are included.

SST Simple Cycle Combustion Turbines – 25 

MW

Nameplate capacity 25 MW or greater & 33% capacity

factor & 219,000MWh

IGCC IGCC IGCCs at: Wabash, Polk, Edwardsport