Carbon Footprint of Electricity: CO2 Emissions Per Kilowatt, Types of Power

Kim Williamson, Author 8 Billion TreesWritten by Kim Williamson

Carbon Offsets Credits | February 9, 2024

Person wishes to understand the carbon footprint of electricity, including the carbon emissions per kilowatt of electricity by types of power, and co2 of electric generation.

The United States has an energy-intensive infrastructure and economy, but globally, the carbon footprint of electricity varies from country to country.

Because many nations rely on mostly coal to fuel electricity generation, finding ways to reduce the emissions worldwide is a challenge.

However, research and study of carbon dioxide emissions by type of fuel or electric power is allowing some countries like the U.S. to re-conceptualize electricity generation.

This article explores the nuances of the carbon footprint of electricity generation in the U.S. and examines the best and worst fuel types for the environment.

Carbon Footprint of Electricity by Fuel Type and CO2 Emissions per kWh by Fuel Type

The ability to look at and analyze the carbon footprint of electricity by fuel type has provided countries around the world an opportunity to make smarter decisions in electric generation and planning.

There are some very obvious winners and losers in the CO2 emissions race.

Graph showing carbon emission per kilowatt hour by electricity type including coal, biomass, natural gas, solar, wind, nuclear, hydropower, etc.

(Source: World Nuclear Association34)

The leading sources of electricity generation in the U.S. are still natural gas and coal, which are the largest contributors to CO2 emissions. Of the 4,231 billion kilowatt hours (kWh) of electricity generated in this country in 2022, 60% was from carbon-intensive fossil fuels.

Approximately 40%, 1,687 billion kWh, were from natural gas, and around 20%, or 832 billion kWh, were from coal.11

This shift away from coal towards natural gas is responsible for most of the decreasing energy emissions seen across the country, as gas combustion produces about 50% of the CO2 produced by coal combustion. To further emphasize this disparity in CO2e, the EIA reported that coal was responsible for 847 million metric tons of CO2 in 2022.29

In other words, coal was responsible for approximately 20% of electricity generation and a whopping 55% of CO2 emissions.

Natural gas was responsible for 661 MMmt of CO2 in 2022, a 43% proportion of the total, more in line with its 40% share of electricity generation. These numbers are still not ideal, but they do highlight why the transition away from coal and towards natural gas is so critical while the renewable energy industry is growing.10

Several sources have looked at CO2 emissions per kWh by fuel type. What they found was eye-opening. Believe it or not, coal is not the most carbon-intensive fuel source.

Rather, petroleum is, and petroleum combustion produces approximately 2.44 pounds of CO2e for each kWh generated. Coal produces 2.26 pounds per kWh, and natural gas produces .97 pounds per kWh.

However, petroleum’s carbon impact receives less attention because it is not a leading fuel source in the country.12

The EPA’s Greenhouse Gas Equivalencies Calculator can be used to convert emissions data into a CO2e coefficient that can assist in tracking carbon footprint over time.28

Total United States Carbon Emissions per Annum

Individuals, large and small businesses, and even countries around the world are beginning to take a closer look at their carbon footprints to better understand how humans are driving global warming and what measures can be taken to reverse it.

Aerial photo of factories emitting smoke.

(Image: Marcin Jozwiak31)

Carbon footprint calculation involves examining the carbon dioxide (CO2) and other greenhouse gas (GHG) emissions attributed to a specific entity. Carbon dioxide is the leading greenhouse gas emitted by human activity, followed distantly by methane, nitrous oxide, and fluorinated gasses.

CO2 plus other GHGs are often referred to as CO2e, or carbon dioxide equivalent, and will be referred to as such throughout this article.14

According to a 2022 report by the National Oceanic and Atmospheric Administration (NOAA), greenhouse gas emissions have rapidly risen to unprecedented levels in the atmosphere. These findings are attributed to human behavior of burning (or otherwise using) fuel for energy, subsequently releasing CO2e into the air.15

The Intergovernmental Panel on Climate Change (IPCC) published a 2022 report that traces global emissions to their source. According to this report, global GHG emissions reached approximately 59 gigatons (Gt) of CO2e in 2019.

Nearly 65% of these emissions are carbon dioxide emissions attributed to the burning of fossil fuels and industrial operations.19

United States carbon emissions associated with fossil fuel combustion and industry were second highest only behind China in 2014.14 According to the Environmental Protection Agency (EPA) 2023 report, “Inventory of U.S. Greenhouse Gas Emissions and Sinks,” U.S. CO2e for 2021 was 6,340.2 million metric tons, a 5.2% increase from the previous year.5

What Causes the Most Pollution in the U.S.?

Seeing the astonishing amount of CO2e that citizens, businesses, and entities of the U.S. release into the air each year, it makes sense to wonder what causes the most pollution. Per the EPA, the leading contributors to U.S. GHG emissions are:

  1. Transportation (28%)
  2. Electricity (25%)
  3. Industry (23%)

However, if electricity is removed as a category and parsed out into the other domains for end-use, the leading contributors appear as:

  1. Industry (30%)
  2. Commercial & Residential (30%)
  3. Transportation (29%)

In other words, energy production in the U.S. is a tremendous source of CO2e emissions.25

The U.S. Environmental Protection Agency (EPA) Carbon Footprint Calculator can be used to estimate an individual’s carbon footprint in various areas, including home energy use.27

Carbon Footprint of Electricity in the United States

According to the Energy Information Administration (EIA), the United States consumed 16% of the world’s 603 quadrillion British thermal units (Btu) in the year 2021, relative to 4% of the total population. With the U.S.’ 98 quadrillion Btus, the country ranked 10th in energy consumption per capita.9

With this amount of energy consumption, the carbon footprint of electricity in the United States takes on a monstrous aspect. In fact, CO2e emissions from the electric sector increased by 102 million metric tons (MMmt), a 7% bump, in the year 2021, in line with the 3% increase in electricity generation, equivalent to 109 terawatt hours (TWh).22

However, this belies an overall downward trend in energy sector emissions in the last two decades; in fact, CO2 energy-related emissions have decreased by 35% since 2005.8

In total, the CO2e emissions from the electric sector, generated by combustion, were 1,539 million metric tons in the year 2022.10 According to a report by the Congressional Budget Office, these emissions make up 30% of carbon dioxide emitted in the U.S.8

The EIA State Energy Portal also offers data on the carbon intensity of electricity in each state and the associated CO2 emissions.18 For example, the states of West Virginia and Kentucky have the highest rates of coal-fired electricity generation, making the electric generation in these states more carbon-intensive.21

The EPA’s Household Carbon Footprint Calculator can be used to estimate how many watts to run a household in the United States, factoring in the carbon intensity of location.30

How Does Electricity Affect Climate Change?

Electricity has been such a fundamental part of modern civilization that most people could not imagine a life without it. Many may struggle to understand how something that has been an integral part of human life for so long can have such a negative environmental impact.

This section looks to answer the question: “How does electricity affect climate change?” The simplest explanation is that the generation of electricity results in greenhouse gas emissions.

Usually, these emissions are produced during combustion, the process of burning a fuel source such as gas or coal to produce energy which can be transferred into electric power.

The GHG emissions are how electricity directly impacts the environment. When greenhouse gasses such as carbon dioxide and nitrous oxide are released into the atmosphere, they insulate the earth like a blanket, trapping the sun’s heat inside.4

In other words, electricity generation is steadily heating the earth’s atmosphere, impacting climate on all levels, from glacial melting to desertification to habitat destruction.

Additionally, as the earth’s carbon sinks, the ocean and forests, for example, struggle to absorb the excess CO2, they are also impacted. The ocean’s acidification is an example of this.23

Examining the impact electricity has had on climate change over time, it becomes very clear how dire the situation is. According to NASA, the temperature of the earth has increased by 1.9 degrees Fahrenheit since the year 1880.

Remember that a 5-degree drop in temperature resulted in the Ice Age, and a 2-degree rise begins to seem more dangerous.24

Environmental Impact of Renewable Energy vs. Fossil Fuels

The coal industry and advocates of fossil fuel combustion try to focus on the disadvantages of renewable energy to deter progress toward clean energy and maintain profit margins. While it is true that many aspects of the U.S. economy rely heavily on fossil fuel industries, it is not sustainable.

Most of the discussion around renewable energy vs fossil fuels is dramatically favorable towards renewable energy sources in reducing the carbon footprint of electricity.

However, there are a few drawbacks to some renewable sources. For example, large solar and wind power facilities require major tracts of land.

In some areas, this may be desert terrain, but in many states, it requires clearing agricultural and forested land. Another real drawback is the end-of-life treatment of solar and wind power equipment can create a serious waste issue.

To limit the environmental impact of renewable energy sources, the materials should be recycled and reprocessed.

Carbon Free Energy Sources

The MIT Climate Portal examines the difference between renewable energy and carbon free energy.17

Although these two concepts often overlap and a given energy source can be both ‘renewable’ and ‘carbon-free,’ the two terms are distinct and should not be used interchangeably.

No electricity generation is truly carbon free. The emissions used to create the generation play a role.

Graphic that shows the different renewable and carbon free energy sources.

(Solar Power Image: fabersam35, Geothermal Power Image: WikiImages36)

As explained above, renewable energy is derived from sources that cannot be exhausted or depleted. Even if the source is consumed in creating the energy, as long as that source can be replenished, it is considered renewable.

The term ‘carbon-free energy’ alludes only to the absence of CO2e emissions during energy production and consumption, and does not necessarily mean that there are no harmful environmental effects associated with the energy type.

For example, a nuclear power plant does not emit greenhouse gasses during operation and energy production. However, it relies upon an exhaustible resource, uranium, and creates harmful waste products.

Even with its carbon-free label, nuclear power can be made greener by reprocessing waste materials.20 Thus, an energy source can be renewable but not carbon-free, or vice versa, and some types of energy can be both.

Fossil fuels are a prime example of an energy type that is neither renewable nor carbon-free. The limited fossil fuel deposits on Earth make it non-renewable, and the carbon emissions from burning fossil fuels mean it isn’t carbon-free.

The following table provides an illustration of this differentiation.

Examples of Renewable and Carbon-Free Energy Sources
Renewable OnlyCarbon-Free OnlyRenewable (and considered) Carbon-Free
Biomass, Biowaste, Bioenergy, etc.Nuclear Power

Large Hydroelectric Power

Wind Power
Solar Power
Hydroelectric Power
Geothermal Power

Carbon Footprint of Solar Panels

In reviewing solar energy facts, some pros and cons of solar energy become apparent. The major benefits of solar power include:

  • Energy from the sun is an infinite (relatively so) and free resource.
  • Solar energy production is almost entirely carbon-free!
  • The cost of solar energy is decreasing.
  • Solar power installations can function for decades with minimal maintenance.
  • Solar panels are capable of reducing atmospheric CO2e by more than 140x a same-size forest!7

These incredible benefits must be weighed against the carbon footprint of solar panels, the primary arguing point against solar energy. Even though solar power is carbon-free and renewable, it does have an environmental cost, which can be measured by examining solar panel carbon footprint.

Photo of solar panels in an open field.

(Image: Mariana Proença32)

The carbon footprint of solar panels is the aggregate of all of the following:

  • CO2e emissions from mining materials.
  • CO2e emissions from solar panel production (electricity to power the company).
  • CO2e emissions from shipping and transporting panels.
  • CO2e emissions from end-of-life process (recycling, disposing, etc.).

An exact estimate of the total carbon footprint is not yet available, but experts agree that solar energy’s carbon footprint can be drastically reduced by using clean and renewable energy sources to power production plants.7

How Much Power Does a Solar Panel Produce?

As solar technology continues advancing, consumers are wondering “How much power does a solar panel produce?”

Solar panel output depends on the type of panel and location, but on average, a single solar panel can generate around 1.5 kilowatt hours (kWhs) of electricity each day.6 According to the Energy Information Administration, the average U.S. home uses 889 kWh per month, or 29 kWhs per day.13

Best Alternative to Wind or Solar Power

When people hear the term “clean energy,” most people will immediately think of solar energy and many will also think of wind power, but there are many alternatives to consider.

In recent years, much of the renewable energy dialogue has centered on the debate between wind power and solar power with advocates of each insisting that the future lies in one direction or another. Both technologies have made strides across the United States, in the last two decades in particular.

However, wind power has grown more rapidly, accounting for nearly a quarter of the nation’s renewable energy production (compared to 10% for solar). Yet, solar energy systems seem to be more favorable for residential settings.1

There is more than one alternative to wind or solar power that is likely to get overlooked. Hydroelectric power has been in play for a long time, and while large-scale dams create their own set of issues, smaller-scale hydroelectric can be incredibly efficient and microsystems are available to homeowners.

Hydropower accounts for 6.3% of the U.S. total energy production (compared to 9.2% for wind power and 2.8% for solar), according to the Office of Energy Efficiency & Renewable Energy.26

Wide shot of a nuclear plant, an alternative to wind or solar energy, emitting smoke.

(Image: Jonas Denil33)

Many people may not realize that the carbon footprint of nuclear power is rather low. The primary carbon emissions associated with nuclear energy are involved in the mining of uranium and other materials and the construction of the nuclear power plant.

Once operational, nuclear power plants do not emit carbon dioxide or other greenhouse gasses into the atmosphere.16

Although the United States is ranked 10th in the world for energy consumption per capita, emissions from the energy sector have been gradually decreasing for the last 17 years.

This positive trend reflects the country’s shift away from the most carbon-intensive energy sources.

The steps the U.S. has already taken to reduce the carbon footprint of electricity in the country, as well as the downward trending CO2e emissions in the energy sector for the last few years is encouraging.

Frequently Asked Questions About the Carbon Footprint of Electricity

What is a Carbon Footprint?

There are many terms that have come into regular use in discussions about global warming and climate change, including “What is a carbon footprint?” ‘Carbon footprint’ is a term which refers to the total output of greenhouse gasses (Greenhouse gasses = carbon dioxide, methane, nitrous oxide = CO2 equivalent or CO2e) attributed to a specific source (See University of Michigan’s Carbon Footprint Factsheet).3

Do Electric Cars Pollute the Air?

According to the Department of Energy (DOE) Alternative Fuels Data Center, electric vehicles are not responsible for direct pollution as they do not have tailpipe emissions. However, the upstream emissions required in production, energy sources for electric supply, and end of life emissions do have a variable polluting effect on the environment.2


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