Greenhouse gas emissions from nuclear electricity: low, but not zero

Leading climate scientists and most world leaders believe industrialized countries like the US will need to reduce greenhouse gas (GHG) emissions by about 80% by 2050 to help keep the global average temperature from rising more than 2 degrees Celsius above preindustrial levels. Nuclear power, which provides about 20% of US electricity today, looks pretty attractive when compared to coal and gas power, which together provide about 70% of US electricity and account for the majority of the GHG emissions from electricity generation today. But even nuclear power generation causes some GHG emissions.

How big are GHG emissions from nuclear? To properly answer this question, it’s important to consider “lifecycle” emissions, including mining, enriching, and transporting uranium, plus construction, operation, and decommissioning of the power plant, as well as waste handling and disposal. Each of these activities is carried out with some consumption of fossil fuels, and as a consequence, some GHG emissions. One analysis of 103 studies of the GHG emissions associated with nuclear electricity concluded that the emissions per kilowatt hour (kWh) vary with the assumptions used in the analysis, ranging from 1.4 grams of CO2-equivalent (gCO2e) per kWh of electricity generated to 288 gCO2e/kWh, with a mean value of 66 gCO2e/kWh. (CO2e takes into account emissions of CO2, as well as emissions of methane and other greenhouse gases expressed in terms of the amount of CO2 having the equivalent warming effect — radiative forcing in technical jargon). Any value within the full range of these estimates makes nuclear GHG emissions far lower than emissions from existing coal or natural gas power plants. The table below shows that if we accept the 66 gCO2e/kWh as a representative figure, emissions are also lower than emissions from fossil fuel power plants that would use CO2 capture and storage. But nuclear electricity emissions would not be lower than those associated with electricity from wind or solar plants.

Lifecycle Greenhouse Gas Emissions gCO2-e/kWh

Today’s Fossil Fuel Plants


     Coal (a)


     Natural gas (b)


“Low-GHG” Plants


     Wind (c)


     Solar PV (d)


 Nuclear (e)


     Natural gas with CCS (f)


     Coal with CCS (f)


     Biomass with CCS (f,g)

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(a)   Emissions associated with typical existing coal plant in US (32.8% higher heating value efficiency), including from coal mining, processing, delivery to power plant, and combustion. [Climate Central estimate based on work at Princeton University.]

(b)   This estimate is for emissions associated with a new natural gas fired combined cycle power plant operating with an efficiency of 50.8% (higher heating value basis). Emissions include those associated with natural gas production, delivery to power plant, and combustion. [Climate Central estimate based on work at Princeton University.]

(c)    Average of range 2 to 29 cited by America’s Energy Future Panel on Electricity from Renewable Resources.

(d)   Range of 29 to 35 for different solar PV technologies (e.g, amorphous vs. single-crystal silicon) for electricity generation in a Southern European location.

(e)   See Sovacool, 2008.

(f)    Includes production of the fuel and conversion to electricity in combined cycle power plants. Coal and biomass are gasified to produce the gaseous fuel needed by a combined cycle. In all cases, 90% of CO2 available at point of capture in the plant is assumed to be captured and stored below ground. [Climate Central estimate based on work at Princeton University.]

(g)   Emissions are negative for this case, because the CO2 that is captured at the power plant and stored underground is of photosynthetic origin. In other words, the biomass used at the power plant grew by absorbing CO2 from the atmosphere before being harvested and brought to the plant where the CO2 is redirected into underground storage.