---
title: "Life-cycle greenhouse gas emissions of energy sources"
chunk: 1/2
source: "https://en.wikipedia.org/wiki/Life-cycle_greenhouse_gas_emissions_of_energy_sources"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:36:14.271215+00:00"
instance: "kb-cron"
---

Greenhouse gas emissions are one of the environmental impacts of electricity generation. Measurement of life-cycle greenhouse gas emissions involves calculating the global warming potential (GWP) of energy sources through life-cycle assessment. These are usually sources of only electrical energy but sometimes sources of heat are evaluated. The findings are presented in units of global warming potential per unit of electrical energy generated by that source. The scale uses the global warming potential unit, the carbon dioxide equivalent (CO2e), and the unit of electrical energy, the kilowatt hour (kWh). The goal of such assessments is to cover the full life of the source, from material and fuel mining through construction to operation and waste management.
In 2014, the Intergovernmental Panel on Climate Change harmonized the carbon dioxide equivalent (CO2e) findings of the major electricity generating sources in use worldwide. This was done by analyzing the findings of hundreds of individual scientific papers assessing each energy source. Coal is by far the worst emitter, followed by natural gas, with solar, wind and nuclear all low-carbon. Hydropower, biomass, geothermal and ocean power may generally be low-carbon, but poor design or other factors could result in higher emissions from individual power stations.
For all technologies, advances in efficiency, and therefore reductions in CO2e since the time of publication, have not been included. For example, the total life cycle emissions from wind power may have lessened since publication. Similarly, due to the time frame over which the studies were conducted, nuclear Generation II reactor's CO2e results are presented and not the global warming potential of Generation III reactors. Other limitations of the data include: a) missing life cycle phases, and, b) uncertainty as to where to define the cut-off point in the global warming potential of an energy source. The latter is important in assessing a combined electrical grid in the real world, rather than the established practice of simply assessing the energy source in isolation.

== Global warming potential of selected electricity sources ==

1 see also environmental impact of reservoirs#Greenhouse gases.

List of acronyms:

PC — pulverized coal
CCS — carbon capture and storage
IGCC — integrated gasification combined cycle
SC — supercritical
NGCC — natural gas combined cycle
CSP — concentrated solar power
PV — photovoltaic power

== Bioenergy with carbon capture and storage ==
As of 2020 whether bioenergy with carbon capture and storage can be carbon neutral or carbon negative is being researched and is controversial.

== Studies after the 2014 IPCC report ==
Individual studies show a wide range of estimates for fuel sources arising from the different methodologies used. Those on the low end tend to leave parts of the life cycle out of their analysis, while those on the high end often make unrealistic assumptions about the amount of energy used in some parts of the life cycle.
Since the 2014 IPCC study some geothermal has been found to emit CO2 such as some geothermal power in Italy: further research is ongoing in the 2020s.
Ocean energy technologies (tidal and wave) are relatively new, and few studies have been conducted on them. A major issue of the available studies is that they seem to underestimate the impacts of maintenance, which could be significant. An assessment of around 180 ocean technologies found that the GWP of ocean technologies varies between 15 and 105 g/kWh of CO2eq, with an average of 53 g/kWh CO2eq. In a tentative preliminary study, published in 2020, the environmental impact of subsea tidal kite technologies the GWP varied between 15 and 37, with a median value of 23.8 g/kWh), which is slightly higher than that reported in the 2014 IPCC GWP study mentioned earlier (5.6 to 28, with a mean value of 17 g/kWh CO2eq).
In 2021 UNECE published a lifecycle analysis of environmental impact of electricity generation technologies, accounting for the following impacts: resource use (minerals, metals); land use; resource use (fossils); water use; particulate matter; photochemical ozone formation; ozone depletion; human toxicity (non-cancer); ionising radiation; human toxicity (cancer); eutrophication (terrestrial, marine, freshwater); ecotoxicity (freshwater); acidification; climate change, with the latter summarized in the table above.
In June 2022, Électricité de France publishes a detailed Life-cycle assessment study, following the norm ISO 14040, showing the 2019 French nuclear infrastructure produces less than 4 g/kWh CO2eq.

== Cutoff points of calculations and estimates of how long plants last ==
Because most emissions from wind, solar and nuclear are not during operation, if they are operated for longer and generate more electricity over their lifetime then emissions per unit energy will be less. Therefore, their lifetimes are relevant.
Wind farms are estimated to last 30 years: after that the carbon emissions from repowering would need to be taken into account. Solar panels from the 2010s may have a similar lifetime: however how long 2020s solar panels (such as perovskite) will last is not yet known. Some nuclear plants can be used for 80 years,  but others may have to be retired earlier for safety reasons. As of 2020 more than half the world's nuclear plants are expected to request license extensions, and there have been calls for these extensions to be better scrutinised under the Convention on Environmental Impact Assessment in a Transboundary Context.
Some coal-fired power stations may operate for 50 years but others may be shut down after 20 years, or less. According to one 2019 study considering the time value of GHG emissions with techno-economic assessment considerably increases the life cycle emissions from carbon intensive fuels such as coal.

== Lifecycle emissions from heating ==

For residential heating in almost all countries emissions from natural gas furnaces are more than from heat pumps. But in some countries, such as the UK, there is an ongoing debate in the 2020s about whether it is better to replace the natural gas used in residential central heating with hydrogen, or whether to use heat pumps or in some cases more district heating.

== Fossil gas as bridge fuel ==

== Missing life cycle phases ==