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Electricity Transmission is Key to Unlock the Full
Potential of the Inflation Reduction Act
September 2022

Electricity Transmission is Key to Unlock the Full Potentialof the Inflation Reduction Act
Jesse D. Jenkins1, Jamil Farbes2, Ryan Jones2, Neha Patankar3, Greg Schivley4
1.
2.
3.
4.

Princeton University, Zero-carbon Energy Systems Research and Optimization Laboratory (ZERO Lab)
Evolved Energy Research
Binghamton University
Carbon Impact Consulting

Suggested citation: Jenkins, J.D., Farbes, J., Jones, R., Patankar, N., Schivley, G., “Electricity Transmission is Key to Unlock the Full Potentialof the Inflation Reduction Act,” REPEAT Project, Princeton, NJ, September 2022. DOI: 10.5281/zenodo.7106176
This version updated September 22, 2022

Access and download data and other resources at repeatproject.org
Funding for the REPEAT Project was provided by a grant from the Hewlett Foundation.

2

Introduction
This report assesses the role of electricity transmission in enabling the full emissions reduction potential of the Inflation Reduction Act (IRA).
Previously, REPEAT Project estimated that IRA could cut U.S. greenhouse gas emissions by roughly one billion tons per year in 2030 andreduce cumulative greenhouse gas emissions by 6.3 billion tons of CO2-equivalent over the decade (2023-2032).1 That outcome depends on
more than doubling the historical pace of electricity transmission expansion over the last decade in order to interconnect new renewable
resources at sufficient pace and meet growing demand from electric vehicles, heat pumps, and other electrification.
While our modeling finds this outcome makes economic sense, current transmission planning, siting, permitting and cost allocation
practices can all potentially impede the real-world pace of transmission expansion. We thus model the impact of constrained growth in U.S.
electricity transmission on emissions outcomes and the pace of renewable electricity expansion under IRA.

1. Jenkins, J.D., et al., “Preliminary Report: The Climate and Energy Impacts of the Inflation Reduction Act of 2022 ,” REPEAT Project, Princeton, NJ, August 2022. DOI: 10.5281/zenodo.6992940

3

Summary of Findings•

Failing to accelerate transmission expansion beyond the recent historical pace (~1%/year) increases 2030 U.S. greenhouse emissions by ~800
million tons per year, relative to estimated reductions in an unconstrained IRA case. Emissions are 200 million tons higher if transmission growthis limited to 1.5%/year.

•

Over 80% of the potential emissions reductions delivered by IRA in 2030 are lost if transmission expansion is constrained to 1%/year, and roughly
25% are lost if growth is limited to 1.5%/year.

•

To unlock the full emissions reduction potential of the Inflation Reduction Act, the pace of transmission expansion must more than double therate over the last decade to reach an average of ~2.3%/year. That rate of expansion is comparable to the long-term average rate of transmission
additions from 1978-2020.

•

To achieve IRA’s full emissions reduction potential, new clean electricity must be rapidly added to both meet growing demand from electrification
and reduce fossil fuel use in the power sector. Constraining transmission growth severely limits the expansion of wind and solar power.

•

If electricity transmission cannot be expanded fast enough, power sector emissions and associated pollution and public health impacts could
increase significantly as gas and coal-fired power plants produce more to meet growing demand from electric vehicles and other electrification
spurred by IRA.

•

If transmission cannot be expanded faster than recent historical rates (~1%/year), growing demand from electric vehicles and otherelectrification spurred by IRA results in over 110 million tons of additional coal consumption in 2030 than a No IRA case and roughly 250 million
tons more than if transmission expansion is unconstrained.

•

Expanding transmission more rapidly enables growth of wind and solar power and substantially reduces U.S. natural gas consumption, whichfalls 17% from 2021 levels in the unconstrained IRA case. In contrast, if transmission expansion is limited to 1%/year, natural gas use increases
to 4% above 2021 levels in 2030 and remains elevated through 2035.

4

Cumulative Expansion of U.S. High-Voltage Transmission Capacity
Percent growth in GW-miles vs 2020 installed capacity1

45%
40%
35%
30%

IRA unconstrained case(~2.3%/yr average expansion)

Previous REPEAT Project modeling of IRA entails high-voltage transmission expandingat ~2.3%/year, increasing 25% over 2020 levels by 2030 and 41% by 2035.
That pace is more than double the ~1%/year rate that has prevailed over the past
decade and slightly faster than the ~2%/year average expansion rate from 1978-2020.2

IRA ~2%/yr transmission
expansion constraint

To explore the impact of slower transmission expansion, this study explores threealternative scenarios which constrain expansion to ~1%, 1.5%, and 2% per year.

IRA ~1.5%/yr transmission
expansion constraint

25%
IRA ~1%/yr transmission
expansion constraint

20%
15%
10%
5%
0%
2022

2024

2026

2028

2030

2032

2034

1 – Relative to approximately 200,000 GW-miles of estimated installed high voltage (200 kV and above) transmission capacity based on U.S. DOE “Annual U.S. Transmission Data Review,” March 2018.
2 – Based on US DOE, UT Austin and S&P Global data sources as reported in Cembalest (2022), “Eye on the Market 12th Edition: 2022 Annual Energy Paper” p.12.

5

Total Modeled U.S. High-Voltage Transmission Capacity
GW-miles vs 2020 installed capacity1

300,000

IRA ~1%/yr transmission
expansion constraint

IRA ~1.5%/yr transmission
expansion constraint

solar PV
interconnection

IRA unconstrained case(~2.3%/yr avg expansion)

IRA ~2%/yr transmission
expansion constraint

onshore windinterconnection

250,000

offshore windinterconnection

200,000

inter-regionaltransmission
non-modeledtransmission

150,000

100,000

50,000

2035

2032

2030

2028

2026

2024

2022

2020

2035

2032

2030

2028

2026

2024

2022

2020

2035

2032

2030

2028

2026

2024

2022

2020

2035

2032

2030

2028

2026

2024

2022

2020

0

1 – Relative to approximately 200,000 GW-miles of estimated installed high voltage (200 kV and above) transmission capacity based on U.S. DOE “Annual U.S. Transmission Data Review,” March 2018.

6

Impact of Transmission Expansion Constraints on Modeled Net U.S. Greenhouse Gas Emissions (Including Land Carbon Sinks)
billion metric tons CO2-equivalent (Gt CO2-e)1
Historical emissions2

6.5
6.0

Modeled emissions

2005 emissions2:~6.6 billion tons
2021 emissions2:~5.6 billion tons

5.5

No IRA (IIJA only):~4.8 billion tons in 2030(~27% below 2005)3
IRA 1%/yr trans. expansion case
~4.6 billion tons in 2030(~30% below 2005)4

5.0
4.5

IRA 1.5%/yr trans. expansion case
~4.0 billion tons in 2030(~39% below 2005)4

4.0

IRA unconstrained case(~2.3%/yr trans. Expansion)~3.8 billion tons in 2030(~42% below 2005)4

3.5
3.0
2005

2010

2015

2020

2025

2030

Net-Zero Pathway(50% below 2005)

Failing to accelerate transmission
expansion beyond the recent historicalpace (~1%/year) increases 2030 U.S.
greenhouse emissions by ~800 million
tons per year, relative to estimatedreductions in an unconstrained IRA case.
Emissions are 200 million tons higher
if transmission growth is limited
to 1.5%/year.
To unlock the full emissions reduction
potential of the Inflation Reduction Act,the pace of transmission expansion must
more than double the rate over the last
decade to reach an average of~2.3%/year.
That rate of expansion is comparable tothe long-term average rate oftransmission additions from 1978-2020.

1 - CO2-equivalent emissions calculations use IPCC AR4 100 year global warming potential as per EPA Inventory of Greenhouse Gas Emissions and Sinks. All values should be regarded as approximate given uncertainty in future outcomes.
2 - Historical data from US EPA Inventory for 2005-2030; 2021 preliminary emissions estimate assumes total net emissions change in proportion to 6.7% year-on-year change in CO2 emissions from energy and industrial processes estimated by Global Carbon Monitor.
3 - Modeled emissions exclude any changes in passenger and freight miles traveled due to surface transportation, rail, and transit investments in IIJA. According to the Georgetown Climate Center, emissions impact of these changes depend heavily on state implementation of funding
from IIJA, which could result in anywhere from -14 Mt to +25 Mt change in CO2 emissions from transportation in 2030.
4 - Results reflect average of estimated high and low oil & gas production scenarios, which span +/- 20 Mt CO2-e in 2030 (see p. 13-14). Impact on land carbon sinks based on analysis by Energy Innovation.

7

Annual Change in Net U.S. Greenhouse Gas Emissions Relative to No IRA (Bipartisan Infrastructure Law Only)
million metric tons CO2-equivalent (Mt CO2-e)1-280

If electricity transmission cannot be expanded fast enough, power
sector emissions could increase significantly as gas and coalfired power plants produce more to meet growing demand fromelectric vehicles and other electrification spurred by IRA.

Over 80% of the potential emissions reductionsdelivered by IRA in 2030 are lost if transmission
expansion is constrained to 1%/year, and roughly
25% are lost if growth is limited to 1.5%/year

Notes:
1 - CO2-equivalent emissions calculations use IPCC AR4 100 year global warming potential as per EPA Inventory of Greenhouse Gas Emissions and Sinks.
All values should be regarded as approximate given uncertainty in future outcomes. Results rounded to nearest 10 Mt CO2-e. See additional notes on prior page.

8

Annual Average Capacity Additions
Annual Average Capacity Additions

Tech||Outputs Group Aggregate
solar

gigawatts
GW

IRA – ~2%/yrIRA
IRA
IRA
trans.
expansiontrans.
expansiontrans.
IRA
with expansion
Tx limits - 1%
IRAlimitswith Tx limits- 1.5% Tx limits
IRA with Tx limits - 2%
w/1.5%/yr Tx
w/2%/yr
w/1%/yr
Tx limits
base

No IRA(IIJA IIJA
only)
(IIJA only)

20..

gas

coal w/cc
129

71
22
20

18
6

27

33
2031 - 2032

22292029 - 2030

2033 - 2035

1225

16 20276- 2028

38
2025 - 2026

29

72

8
2022 - 2024

6

71

16

33

6

18

102 72

39

36

30
9 6
2033 - 2035
39

13
13
2031 - 2032 6

2027
7 - 2028102025 - 2026

312029 - 2030 4 5

14

45

6

39

29
11
2022 - 2024

7 47

31

80

20

7
12
2033 - 2035

2031 - 2032 7 10

7

24
105

25
12

75
2029 - 2030 3 5 9 7102025 - 2026

2027 - 2028

39
49

38

29
11

20

2022 - 2024

102

47
80

49

105

75

89
106

75

49
20

889
12

7 - 2035
2033

8

12
2031 - 2032 7 10

5 7 72029 - 2030

25

106
24

22
12
2025 - 2026

2027 - 2028

29112022 - 2024

75

4 9 496 152033 - 2035

162031 - 2032 5

12

7

20

2029 - 2030 5 6

20

22

44
29
9
8

8 - 2028
2027

129

122
107

126

122
64

20

41

42

107

63

92

126
33
2025 - 2026

13 5
142022 - 2024

2292
14 5 72033 - 2035

2031 - 2032

64412027 - 2028

2025 - 2026

20

2029 - 2030 5 6

33

8

29

0

19

20

2022 - 2024 7

46

7

49

19

40

17

37

80

7

9

12
5

38

29

13
3

30

6

45

39

29

14

7

12

9 7

39

24

38

29

20
8

12

7

24

22

29

15

Sum of annual average for each Year (group) broken down by Run Name (copy). Color shows details about Tech||Outputs Group Aggregate. The marks are labeled by sum of annual average. Details are shown forType. The data is filtered on Tech||Outputs Group Detailed, Yr filter - first and Yr filter - last. The Tech||Outputs Group Detailed filter excludes rooftop solar. The Yr filter - first filter keeps True. The Yr filter - last filter
keeps True. The view is filtered on Type, Tech||Outputs Group Aggregate and Run Name (copy). The Type filter keeps new. The Tech||Outputs Group Aggregate filter keeps 7 members. The Run Name (copy) filter
excludes House and Frozen Policy.

6

gas w/cc

coal w/cc
gas

100

42

onshore windgas w/cc

120

63

offshore wind

nuclearnuclearConstraining transmission growth severely limits
the expansion of wind and solar power.

140

16

Tech||Outputs Group Aggregate
solar offshore wind

Pathway

Net-Zero Pathway

onshore wind

36

160

60

Net-ZeroNet-Zero
Pathway

To achieve IRA’s full emissions reduction potential,
new clean electricity must be rapidly added to both
meet growing demand from electrification andreduce fossil fuel use in the power sector.

180

2

IRA
Net-Zero caseunconstrained
IRA
Pathway

IRA – ~1.5%/yr
NowithIRA Tx limits - 1.5%IRA – ~1%/yr IRA withIRA
IRA Tx limits - 2% IRA

- 1%

9

U.S. Coal Consumption

If transmission cannot be expanded faster than recent historical rates(~1%/year), growing demand from electric vehicles and otherelectrification spurred by IRA results in over 110 million tons of additional
coal consumption in 2030 than a No IRA case and roughly 250 million tons
more than if transmission expansion is unconstrained.

million short tons per year
700
633

600

555
528

500

460461 463
425

400

434

449
421
407

No IRA (IIJA only)
IRA - ~1%/yr
transmission expansion

545

537

IRA - ~1.5%/yr
transmission expansion

511
457

441

432

429
402

398
348
325

300

369
304
291

334
303
296

343
320
297

2032

2035

IRA - ~2%/yr
transmission expansion
IRA - unconstrained case

200

100

0
2022

2024

2026

2028

2030

10

Change in U.S. Natural Gas Consumption vs 2021
trillion cubic feet per year
4.0
3.0
2.0

Expanding transmission more rapidly enables growth of wind and solar powerand substantially reduces U.S. natural gas consumption, which falls 17% from2021 levels in the unconstrained IRA case.

No IRA (IIJA only)

In contrast, if transmission expansion is limited to 1%/year, natural gas use
increases to 4% above 2021 levels in 2030 and remains elevated through 2035.

IRA - ~1%/yr
transmission expansion

1.2

1.0

1.0

IRA - ~1.5%/yr
transmission expansion

1.3

1.1

0.0

IRA - ~2%/yr
transmission expansion-1.0

IRA - unconstrained
case

0.2

-0.7

-2.0
-3.0

-1.5

-1.8 -1.8

-2.3
-2.8

-2.9

-2.0
-3.0

-4.0

-3.8 -3.8

-5.0

-3.5

-3.7
-4.7 -4.6

-3.9
-4.5

-4.5
-4.9

-5.0

-6.0
2024

2026

2028

2030

2032

2035

11

CO2 Emissions
million metric tons

IRA withPowerTx limits- 1% Annual
IRA withCO2
Tx limits- 1.5%
SectorEmissionsmillion metric tons

IRA – ~1%/yr
trans.
IRA
with expansion
Tx limits - 1%

No IRA(IIJA
IIJAonly)

IRA with Tx limits - 2%
IRA – ~1.5%/yr
trans.
expansion
IRA
with Tx
limits - 1.5%

IRA

IRA – ~2%/yr
trans.
IRA
withexpansion
Tx limits - 2%

Net-Zero Pathway
Net-Zero
Pathway
Net-Zero Pathway

IRA
unconstrained
case
IRA

coal and coke
diesel60%

coal and coke

natural gas

diesel

60%

1,400

other
naturalgas fossil
otherfossilgeologicco2 sequestrati..

50%

geologic co2 sequestrati..

50%

1,200

1,000

40%

40%
800

30%

30%

600

80% below 2005 level

20%

400

20%
10%

200

0

0%

10%

-200

2005 electricity emissions
share of share
2005ofelectricity
emissionslPower Sector Annual CO2 Emissions

emissionsnet netemissions

If new transmission capacity cannot be
added at a faster pace, greenhouseemissions from coal and gas-fired
power plants remain high, along withassociated pollution and public healthimpacts.
Accelerating transmission expansion is
critical to reduce power sector
emissions and avoid premature deaths
from air pollution.

-10%

2025

2030
Year

2035

2025

2030
Year

2035

2025

2030
Year

2035

2025

2030
Year

2035

2025

2030
Year

2035

2025

2030

0%

2035

Year

-10%

12

Electricity Generation

terawatt-hours(TWh)
Electricity
Generation
TWh

7K
6K

IRA – ~1%/yr
trans.
expansion
IRA with Tx
limits - 1%

No IRA(IIJAIIJA
only)

solar

fossil w/cc

windfossilhydro & other RE

nuclear

solar

solar

wind

wind

wind

3K

Net-Zero
Pathway
Net-Zero Pathway

solar

solar

wind

solar

4K

2K

IRA – ~2%/yr
trans.
IRA withexpansion
Tx limits - 2%

solar

5K

IRA
unconstrained case
IRA

IRA – ~1.5%/yr
trans.
IRA with expansion
Tx limits - 1.5%

wind

wind

fossilfossilfossilfossilfossilfossil

1K
0K

nuclear2025

nuclear
2030

2035

2025

2030

nuclear
2035

2025

2030

nuclear
2035

2025

nuclearnuclear
2030

2035

2025

2030

2035

2025

2030

2035

Share of Clean Generation
80%
60%

67%

66%

87%

91%

79%

76%

84%

86%

13

About REPEAT Project14

A New Toolkit for Evaluating Energy and Climate Policy
The REPEAT Project provides regular, timely and independent environmental and economic evaluationof federal energy and climate policies as they’re proposed and enacted, offering a detailed look at the UnitedStates’ evolving energy and climate policy environment and the country’s progress on the road to net-zerogreenhouse gas emissions.
Approach: employ geospatial planning and analysis tools coupled with detailed macro-energy system
optimization models to rapidly evaluate federal policy and regulatory proposals at politically-relevant spatial
resolutions (e.g., state, county, and finer resolutions). A refinement of methods used in the Princeton
Net-Zero America study.
Goal: provide independent, timely, and credible information and analysis for broad educational purposes,
including as a resource available publicly for stakeholders, decision-makers, and the media.
Funding: funding for the REPEAT Project was provided by a grant from the Hewlett Foundation.

15

The REPEAT Team
Princeton ZERO Lab: Prof. Jesse D. Jenkins (PI); Dr. Qingyu Xu (postdoc); Annie Jacobson (PhD candidate);
Undergraduate research assistants: Claire Wayner, Aneesha Manocha, Riti Bhandakar, Cady Feng
Dartmouth College: Prof. Erin Mayfield (co-PI);
Binghamton University: Prof. Neha Patankar;
Evolved Energy Research: Ryan Jones, Jamil Farbes (macro-energy systems modeling)
Carbon Impact Consulting: Greg Schivley (scenario inputs, transmission interconnection routing, etc.)
Montara Mountain Energy: Emily Leslie, Andrew Pascale (renewable energy candidate project areas,transmission cost surface).
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