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Technical Support Document (TSD)

for the final Transport Rule

Docket ID No. EPA-HQ-OAR-2009-0491

Resource Adequacy and Reliability in the IPM Projections for the Transport Rule TSD

U.S. Environmental Protection Agency

Office of Air and Radiation

June 2011
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Resource Adequacy and Reliability in the IPM Projections for the Transport Rule

This document describes resource adequacy and reliability results in the IPM 2014 projections 

for the base case and Transport rule policy cases. As used here, the term Resource Adequacy

means the provision of adequate generating resources to meet projected load and generating 

reserve requirements in each region, while Reliability includes the ability to deliver the 

resources to the loads so the overall power grid remains stable. IPM is specifically designed to 

ensure generation resource adequacy, either by using existing resources or through the 

construction of new resources. IPM addresses reliable delivery of generation resources for the 

delivery of electricity between regions, by setting limits to the ability to transfer power 

between regions using the bulk power transmission system. Within each model region, IPM 

assumes that adequate transmission capacity exists to deliver any resources located in, or 

transferred to, the region.

Summary of Changes in Operational Capacity

Total operational capacity is lower in the policy scenario, primarily as a result of increases in 

coal retirement. Since most regions are projected to have excess capacity above their target 

reserve margins, most of these retirements are absorbed by a reduction in reserves that are not 

needed to meet the target level. Operational capacity1changes from the base case in 2014 are 

summarized below:

Table 1. Operational Capacity Summary in 2014

Base case operational capacity (MW) 1,029,215

 Adjusted for Changes in Policy Case:

 (-) Coal retirements -4,772

 (-) Coal capacity derated -487

 (+)New Capacity Additions +73

 (+)Lower non-coal retirements +1,288

 Net Change in Policy Case -3,898

Equals Policy Case Operational Capacity 1,025,3172

Since the model must maintain adequate reserves in each region, the reduced operational 

capacity of 3,898 MW in the policy case is taken from excess reserves that are not needed. In 

order to maintain resource adequacy in each region where coal resources retire, the model 

relies on this excess reserve reduction, on lower retirements of non-coal capacity and on 

 

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Operational capacity is any existing, new or retrofitted capacity that is not retired.

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Numbers in this table may not sum due to independent rounding.
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greater new capacity additions. As the table shows, the reduction in capacity (excess reserves)

is the largest source of change, followed by lower non-coal retirements and new capacity 

additions. Each of these policy case changes is discussed further below.

Notably, the “retirements” examined here are IPM forecasts that could be muted by utility 

decisions to hold on to these generating units and make other changes for compliance, which 

they have the freedom to do under the Transport Rule.

Reduction in Excess Reserves

IPM uses a target reserve margin in each region3as the basis for determining how much 

capacity to keep operational in order to preserve resource adequacy. IPM retires capacity if it is 

no longer needed to provide energy for load or to provide capacity to meet reserve margin 

during the planning horizon of the projections. Since current regional reserves are generally 

higher than the target reserve margin for the region, IPM may retire reserve capacity in 2014 if 

it is not economic to maintain relative to alternatives such as building new capacity or 

transferring capacity from another region. As a result, many of the coal plants that are 

projected to retire in 2014 will not need to be replaced for resource adequacy until later years 

when demand increases and reserves approach the target reserve margin. 

Table 1 above shows that operational capacity is reduced by less than one half of percent 

nationwide in 2014 under the policy. This reduction will have little overall impact, since the 

weighted average reserve margin at the national level are projected to be approximately 25% in 

the base case, compared to a default NERC level of 15%. Moreover, coal retirements are 

distributed throughout the power grid, so there will be only small impacts at the regional level. 

For example, the coal generating areas in western Pennsylvania, West Virginia, Ohio and 

Indiana all have significant excess generation resources: these areas combined see a decrease 

less than 2% in their reserve margins and the reserve margin for the combined area remains

over 20%.4 These excess regional reserves above the target margin can be shared among 

subregion to ensure adequate reserve margins within a larger reliability region. IPM permits 

these transfers of reserves, but limits their level to ensure the reliability of the bulk power 

system (see discussion below.) 

Although there are substantial existing regional variations in reserve margin, IPM adjusts 

regional capacities in 2014 to meet the specific target reserve margin in each region, through 

reduction in non-coal retirements, construction of new generating capacity and transfers of 

 

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Reserve margin targets are generally based on the NERC 2010 10 Year Assessments for the region, except in cases 

where there are more stringent state requirements or other exceptions.

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See map of IPM regions and Table of target and projected reserve margins in the Appendix. The three regions 

referenced in the text are MACW, RFCO and RFCP. 
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capacity among regions to meet the specific reserve margin in each region. Each of these 

adjustments in the 2014 projections is described below.

Reduction in Non-coal Retirements

Reducing non-coal retirements relative to these retirements in the base case is the second 

largest adjustment needed to balance the loss of coal capacity. Overall combined cycle, 

combustion turbine and nuclear retirements are 1,288 MW lower in the policy case compared 

to the base case. Lower combined cycle retirements contribute 126 MW, lower combustion 

turbine 307 MW, and lower nuclear 854 MW to the total capacity made available through 

reduced retirements of non-coal capacity. The distribution of these retirements across IPM 

regions is shown in the Appendix.

New Capacity Additions

Very few new capacity additions are needed to accommodate coal retirements, once excess 

reserves and non-coal retirements relative to the base case are considered. Only 73 MW of 

new capacity are added compared to the base case, all landfill capacity5. 

Reserve Transfers

In cases where it is economic to transfer reserves from a neighboring region rather that supply 

reserves from within a region, IPM will transfer reserves, subject to summer and winter limits 

that are designed to ensure that these reserves can be transferred reliably. The transfer of 

reserves can occur, for example, if a region must retire a large amount of coal capacity that was 

used in the base case to meet reserve requirements. Although there are only a few significant 

differences between the base and policy cases in reserve transfers, some are noteworthy. For 

example, the net decrease in coal capacity in RFCP (838 MW in West Virginia and parts of Ohio) 

is to a large extent offset by a net increase in transfer of reserves into the region (807 MW). 

Reserve transfers by region are provided in the appendix.

 

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Landfill capacity is from generation produced using capture of methane at landfills as a source for power.
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Appendix: Tables by IPM Region

A1. Projected Operational Capacity in 2014

A2. Summary of Target and Projected Reserve Margins in 2014

A3. Policy Case Retired Capacity Incremental to Base Case in 2014

A4. New Capacity in Policy Case Incremental to Base Case in 2014

A5. Capacity Transfers Region in Base and Policy Scenarios in 2014

Map of IPM Regions
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A1. Projected Operational Capacity in 2014(MW)

Non-Coal

All Generation Sources Coal Only Additional

Region Base Policy Change Base Policy Change in Policy

AZNM 35,544 35,560 16 9,845 9,818 -27 43

CA-N 40,930 40,930 0 217 217 0 0

CA-S 32,676 32,676 0 213 213 0 0

COMD 24,699 25,234 535 4,238 4,229 -9 544

DSNY 9,717 9,717 0 369 366 -3 3

ENTG 40,109 40,384 275 8,397 8,397 0 275

ERCT 90,405 89,843 -562 18,456 18,401 -55 -507

FRCC 55,650 55,632 -18 9,191 9,173 -18 0

GWAY 31,970 31,518 -452 19,647 19,009 -638 186

LILC 5,494 5,485 -9 -9

MACE 30,866 30,808 -58 2,438 2,379 -59 1

MACS 12,141 12,122 -19 5,153 5,107 -46 27

MACW 31,295 30,830 -465 11,325 10,860 -465 0

MECS 27,713 27,607 -106 10,926 10,820 -106 0

MRO 50,193 50,249 56 20,796 20,788 -8 64

NENG 33,136 33,480 344 2,697 2,699 2 342

NWPE 19,666 19,657 -9 12,262 12,263 1 -10

NYC 9,333 9,333 0 0

PNW 48,671 48,671 0 1,989 1,989 0 0

RFCO 48,981 48,521 -460 30,773 30,313 -460 0

RFCP 45,347 44,539 -808 33,269 32,431 -838 30

RMPA 18,464 18,417 -47 7,960 7,960 0 -47

SNV 9,196 9,196 0 2,555 2,555 0 0

SOU 62,895 62,845 -50 24,633 24,583 -50 0

SPPN 17,048 17,228 180 8,559 8,125 -434 614

SPPS 40,738 40,355 -383 12,023 12,023 0 -383

TVA 37,846 36,933 -913 13,009 12,096 -913 0

TVAK 13,352 12,997 -355 9,800 9,445 -355 0

UPNY 15,743 15,731 -12 2,295 2,283 -12 0

VACA 49,131 48,679 -452 18,879 18,427 -452 0

VAPW 22,259 22,251 -8 4,333 4,325 -8 0

WUMS 18,007 17,889 -118 8,489 8,183 -306 188

Total 1,029,215 1,025,317 -3,898 314,736 309,477 -5,259 1,361
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A2. Summary of Target and Projected Reserve Margins in 2014 (MW) 

Projected Reserve Margins

IPM Region

Target Reserve 

Margin Base Case Policy Case

AZNM 13.6% 28.7% 28.6%

CA-N 14.6% 17.2% 17.2%

CA-S 14.8% 14.8% 14.8%

COMD 15.3% 18.6% 21.3%

DSNY 18.0% 18.0% 20.8%

ENTG 15.0% 38.8% 37.1%

ERCT 12.5% 25.6% 24.8%

FRCC 19.3% 22.2% 22.2%

GWAY 11.9% 61.7% 59.3%

LILC 18.0% 24.6% 20.4%

MACE 15.3% 15.3% 15.3%

MACS 15.3% 15.3% 15.3%

MACW 15.3% 55.1% 51.2%

MECS 15.3% 47.8% 47.2%

MRO 15.0% 15.0% 15.0%

NENG 15.0% 25.7% 27.1%

NWPE 12.0% 79.0% 78.9%

NYC 18.0% 18.0% 18.0%

PNW 20.0% 44.9% 44.9%

RFCO 15.4% 25.1% 21.3%

RFCP 15.3% 15.3% 15.3%

RMPA 12.3% 12.3% 12.3%

SNV 13.6% 46.6% 46.6%

SOU 15.0% 27.8% 26.7%

SPPN 13.6% 73.2% 75.2%

SPPS 13.6% 20.2% 19.1%

TVA 15.0% 15.5% 15.0%

TVAK 15.0% 41.0% 37.2%

UPNY 18.0% 21.1% 21.0%

VACA 15.0% 15.0% 15.0%

VAPW 15.3% 15.3% 15.3%

WUMS 15.0% 33.5% 32.6%
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A3. Policy Case Retired Capacity Incremental to the Base Case in 2014 (MW) 

IPM Region CC Coal CT Nuclear OG Steam

AZNM 0 27 0 0 0

CA-N 0 0 0 0 0

ENTG 0 0 0 0 -275

ERCT 0 15 0 0 507

GWAY 0 621 0 0 -186

LILC 0 0 0 0 8

MACE 0 55 0 0 0

MACS 0 45 0 0 0

MACW 0 424 0 0 0

MECS 0 82 0 0 0

NENG 0 0 0 0 -344

NWPE 0 0 0 0 0

PNW 0 0 0 0 0

RFCO 0 374 0 0 0

RFCP 0 751 0 0 0

SPPN -126 431 -307 0 -181

SPPS 0 0 0 0 347

TVA 0 915 0 0 0

TVAK 0 326 0 0 0

UPNY 0 0 0 0 0

VACA 0 427 0 0 0

VAPW 0 0 0 0 0

WUMS 0 279 0 -854 123

Grand Total -126 4772 -307 -854 -1
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A4. New Capacity Policy Case Incremental to Base Case in 2014 (MW) 

Region CC CT Wind Other Total

AZNM 0 0 43 0 43

CA-N 0 0 0 0 0

CA-S 0 0 0 0 0

COMD 0 0 0 544 544

DSNY 0 0 3 0 3

ENTG 0 0 0 0 0

ERCT 0 0 0 0 0

FRCC 0 0 0 0 0

GWAY 0 0 0 0 0

MACE 0 0 28 -27 1

MACS 0 0 0 27 27

MACW 0 0 0 0 0

MECS 0 0 0 0 0

MRO 0 0 21 43 64

NENG 0 0 -2 0 -2

NWPE 0 0 -10 0 -10

NYC 0 0 0 0 0

PNW 0 0 0 0 0

RFCO 0 0 0 0 0

RFCP 0 0 0 30 30

RMPA 0 0 -47 0 -47

SNV 0 0 0 0 0

SOU 0 0 0 0 0

SPPN 0 0 0 0 0

SPPS 0 0 -36 0 -36

TVA 0 0 0 0 0

UPNY 0 0 0 0 0

VACA 0 0 0 0 0

VAPW 0 0 0 0 0

WUMS 0 0 0 -544 -544

Total 0 0 0 73 73
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A5. Net Capacity Transfers by IPM Region in Base and Policy Scenarios in 2014 (MW)

(Net outflows are positive; net inflows negative)

Base Case Policy Case Net Change in Policy Case

Region NetWinter NetSummer NetWinter NetSummer NetWinter NetSummer

AZNM 0 2,307 0 2,307 0 0

CA-N 0 3,515 0 3,515 0 0

CA-S 0 -11,014 0 -11,014 0 0

COMD 749 321 749 321 0 0

DSNY 447 2,494 447 2,325 0 -169

ENTG 0 142 0 902 0 760

ERCT 0 0 0 0 0 0

FRCC 0 0 0 0 0 0

GWAY 0 385 0 385 0 0

LILC 0 231 0 399 0 168

MACE 0 -4,414 0 -4,496 0 -82

MACS -899 -2,875 -920 -2,896 -21 -21

MACW 2,860 5,787 2,881 5,870 21 83

MECS 1,968 1,880 1,968 1,880 0 0

MRO 256 -3,072 256 -3,031 0 41

NENG 1,803 0 1,803 0 0 0

NWPE 0 1,966 0 1,966 0 0

NYC -437 -2,670 -437 -2,670 0 0

PNW 0 2,945 0 2,945 0 0

RFCO 1,832 5,944 2,656 6,767 824 823

RFCP -4,432 -6,291 -5,239 -7,098 -807 -807

RMPA 0 87 0 71 0 -16

SNV 0 648 0 648 0 0

SOU 0 699 0 1,188 0 489

SPPN 0 570 0 570 0 0

SPPS 0 0 0 0 0 0

TVA 0 0 0 -745 0 -745

TVAK 0 166 0 166 0 0

UPNY 2,325 1,259 2,325 1,259 0 0

VACA 0 1,131 0 680 0 -451

VAPW 0 -459 0 -466 0 -7

WUMS 0 256 0 256 0 0
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