Nuclear Carbon Intensity

3.6 g

Nuclear CO₂/kWh (operational)

eGRID 2023 — auxiliary systems only

411 g

Gas CC CO₂/kWh (operational)

EPA CEMS 2023 via eGRID

980 g

Coal CO₂/kWh (operational)

EPA CEMS 2023 via eGRID

320 Mt

CO₂ avoided vs gas (2025)

785 TWh × 407 g/kWh delta

$16.3B

Carbon value at $51/ton SCC

IRA Social Cost of Carbon

Key finding: US nuclear's 785 TWh in 2025 avoided approximately 320 million metric tons of CO₂ versus gas-fired replacement — equivalent to taking 70 million cars off the road. Nuclear plants are not monitored by EPA CEMS (no combustion stack), but EPA eGRID assigns ~3.6 g CO₂/kWh for auxiliary diesel systems — 114× less than gas CC, 272× less than coal. At the IRA's Social Cost of Carbon ($51/ton), nuclear's unpriced carbon advantage is worth $20.76/MWh — more than double its entire fuel cost. No state ZEC or federal credit compensates for this fully.

⚡ Operational CO₂ Intensity (EPA eGRID 2023)

g CO₂/kWh — from combustion stack emissions (EPA CEMS) and eGRID supplemental data. Nuclear not in CEMS.

Sources: EPA eGRID2023 (pub. Jan 2025), Table US23 national averages. Gas CC = combined cycle fleet average. Gas peaker = simple cycle / combustion turbine average. Coal = steam electric fleet average. Nuclear note: Nuclear plants are not required to install CEMS (no combustion emissions to monitor). eGRID assigns ~3.6 g CO₂/kWh based on emergency diesel generators and auxiliary systems — not reactor operation.

🔬 Lifecycle CO₂ Intensity (IPCC AR6, 2022)

g CO₂eq/kWh — includes construction, fuel cycle, operations, decommissioning. IPCC AR6 WGIII median values.

Source: IPCC AR6 WGIII (2022) Annex III, Table A.III.2 — median lifecycle GHG emission intensity. Includes all lifecycle stages: materials, construction, fuel supply chain, operations, decommissioning. Nuclear lifecycle includes uranium mining, conversion, enrichment, fabrication, and waste management. Nuclear's lifecycle figure (12 g/kWh) is comparable to wind (11 g/kWh) and 41× lower than gas CC (490 g/kWh).

📉 Annual CO₂ Avoided by US Nuclear Fleet (785 TWh, 2025)

Counterfactual	CO₂/kWh	CO₂ delta/kWh	Annual avoided	Car equivalent
vs. Gas CC	411 g	407 g/kWh	320 Mt CO₂	~70M cars
vs. Gas Peaker	580 g	576 g/kWh	452 Mt CO₂	~98M cars
vs. Coal	980 g	976 g/kWh	767 Mt CO₂	~167M cars

Car equivalent assumes 4.6 metric tons CO₂/vehicle/year (US EPA average). Annual avoided CO₂ = 785 TWh × CO₂ delta per kWh. Nuclear operational emissions = 3.6 g/kWh (subtracted from counterfactual).

Carbon Price	Annual value	Value/MWh nuclear	Context
$30/ton	$9.6B	$12.21/MWh	RGGI range
$51/ton	$16.3B	$20.76/MWh	IRA Social Cost of Carbon
$65/ton	$20.8B	$26.46/MWh	EU ETS (2024 avg)
$100/ton	$32.0B	$40.74/MWh	Biden EPA high-end SCC
$150/ton	$48.0B	$61.11/MWh	IMF recommended floor
$200/ton	$64.0B	$81.53/MWh	DICE model / Nordhaus high

Annual value = 320 Mt CO₂ avoided (vs gas CC replacement) × carbon price. Value/MWh = annual value ÷ 785 TWh. US nuclear receives no direct federal carbon payment for this avoided CO₂.

💰 Total Cost of Electricity — Fuel + Carbon Externality ($/MWh)

Carbon Price	Nuclear fuel cost	Nuclear carbon cost	Nuclear TOTAL	Gas fuel cost	Gas carbon cost	Gas TOTAL	Nuclear advantage
$0/ton (today)	$10.10	$0.04	$10.14	$26.90	$0.00	$26.90	−$16.76 (62%)
$30/ton	$10.10	$0.11	$10.21	$26.90	$12.33	$403	−$29.02 (74%)
$51/ton ← IRA SCC	$10.10	$0.18	$10.28	$26.90	$20.96	$47.86	−$37.58 (79%)
$65/ton	$10.10	$0.23	$10.33	$26.90	$26.72	$53.62	−$43.29 (81%)
$100/ton	$10.10	$0.36	$10.46	$26.90	$41.10	$68.00	−$57.54 (85%)
$150/ton	$10.10	$0.54	$10.64	$26.90	$61.65	$88.55	−$77.91 (88%)
$200/ton	$10.10	$0.72	$10.82	$26.90	$82.20	$109.10	−$98.28 (90%)

Nuclear fuel cost = $10.10/MWh full fuel cycle (FERC Form 1 — see Nuclear Fuel Cost report). Gas fuel cost = $26.90/MWh (EIA Electric Power Annual 2024). Carbon cost = CO₂ intensity × carbon price: nuclear 0.0036 t/MWh × P; gas CC 0.411 t/MWh × P. Nuclear advantage grows monotonically with carbon price — nuclear is a natural carbon hedge. Advantage is independent of uranium spot price — even at $150/lb U3O8, nuclear full fuel cycle ~$13/MWh vs gas $47–109/MWh at any carbon price.

🔬 Data Sources & Methodology

EPA eGRID 2023 (EPA pub. Jan 2025)
Primary source for operational CO₂ intensity by fuel type. eGRID synthesizes EPA CEMS continuous emissions monitoring data (for fossil plants) with supplemental administrative data. National averages used: nuclear 3.6 g CO₂/kWh, gas CC 411 g CO₂/kWh, gas peaker 580 g CO₂/kWh, coal 980 g CO₂/kWh. Available: epa.gov/egrid

EPA CEMS / CAMPD
Continuous Emissions Monitoring System data for individual fossil power plants — SO₂, NOx, CO₂, and heat input at hourly resolution. Nuclear plants are not subject to CEMS requirements (40 CFR Part 75) because they have no combustion stack. eGRID uses CEMS as the primary input for fossil CO₂ figures cited above. Available: campd.epa.gov

IRA Social Cost of Carbon
$51/metric ton CO₂ (2020 dollars), per EPA's 2023 Regulatory Impact Analysis following Interagency Working Group methodology. Used as the primary carbon price reference.

IPCC AR6 WGIII (2022), Annex III Table A.III.2
Lifecycle greenhouse gas emission intensities in g CO₂eq/kWh (median values). Covers all lifecycle stages including construction, fuel supply chain, operations, decommissioning. Nuclear median: 12 g CO₂eq/kWh. Gas CC median: 490 g CO₂eq/kWh. Coal median: 820 g CO₂eq/kWh. Wind onshore median: 11 g CO₂eq/kWh.

EIA Electric Power Annual 2024
US nuclear net generation: 785 TWh (2025). Gas fuel cost: $26.90/MWh. Used for avoided CO₂ and carbon value calculations.

Nuclear fuel cost: $10.10/MWh
Full fuel cycle from FERC Form 1 Account 518 analysis (uranium + conversion + enrichment + fabrication + waste). See Nuclear Fuel Cost per MWh report for detail.