Carbon Intensity of Electricity: g CO₂/kWh by Country and Source

Every kilowatt-hour you use carries a hidden number: the grams of CO₂ released to generate it. This carbon intensity of electricity differs more than thirtyfold between countries and swings hour by hour as the wind picks up or the sun sets. It decides whether an electric car or a heat pump is a big climate win or a modest one. Companies use it for emissions reporting, and it is the best single measure of how far a country’s power sector has decarbonised. Here is how it is measured, where each country stands and how to use it properly.

How carbon intensity is calculated

Every published number rests on a few choices:

• Direct (combustion) vs life-cycle. Direct factors count only stack emissions, so wind, solar, hydro and nuclear come out at zero. Life-cycle factors include construction, fuel supply and methane leakage. Ember and Our World in Data publish life-cycle values (CO₂e) based on IPCC medians.
• Generation vs consumption. Consumption-based intensity adjusts for imports and exports.
• Gross vs net of losses. Grid losses (typically 5–10%) raise the intensity of electricity delivered to your socket. The UK’s DESNZ factors, for example, publish generation and transmission/distribution losses separately.
• Annual average vs hourly. An annual average hides big swings across the day and the seasons.

Emission factors by source

Newer assessments (UNECE 2021) give lower values for solar PV (~8–40 g) and nuclear (~5–6 g), thanks to better manufacturing and cleaner supply chains.

Carbon intensity by country

From the Ember / Our World in Data dataset (latest year, mostly 2025):

Each country has its own page with the full time series. Start at the country index, compare them on the rankings, or see the global picture on the world energy map.

The global trend

World average intensity was roughly 527 g CO₂e/kWh in 2000, peaked around 540–545 g in 2007–2012 as coal expanded in Asia, and has since fallen to about 458 g in 2025 (Ember / OWID). The low-carbon share of generation (renewables + nuclear) rose from about 33% in 2010 to roughly 43% in 2025, almost entirely thanks to solar and wind. Total power-sector emissions are still near record levels, though, at about 14.6 Gt CO₂e, because demand keeps growing.

Some countries have cut much faster. The UK’s intensity has dropped by roughly 60% since 2012 as coal disappeared. Denmark went from around 400–500 g in the early 2000s to near 100 g. Poland, Germany and the US are also well down. Explore any country’s trajectory with the explorer.

Average versus marginal emissions

Average intensity gives the footprint of the electricity you consume, shared equally among all users. Marginal intensity tells you what changes when you add or remove a load. Usually that is a fossil plant ramping up or down, because renewables run whenever they can. On a grid where gas sets the margin, marginal intensity may be 350–450 g/kWh even if the average is 150 g. When renewables are being curtailed because there is too much of them, extra demand can have a marginal intensity near zero.

Hourly variation

Intensity can change by a factor of three or more within a day. In Germany, sunny and windy hours can run below 100 g/kWh, while calm winter evenings can top 500 g/kWh. In California, midday solar pushes intensity down sharply and evenings run on gas. So moving flexible loads in time (EV charging, heat pump preheating, water heating, batteries) cuts emissions as well as costs. Many grid operators and apps publish live and forecast intensity data.

Using carbon intensity for your own footprint

Worked example: is my heat pump cleaner than gas?

• A gas boiler at 90% efficiency: 202 g/kWh gas ÷ 0.9 ≈ 225 g CO₂ per kWh of heat (more with methane leakage).
• A heat pump at SPF 3.2: grid intensity ÷ 3.2.

Even on a coal-heavy grid an efficient heat pump roughly matches a gas boiler, and its emissions drop every year as the grid gets cleaner. Run your own numbers in the electricity CO₂ calculator, heat pump vs gas boiler calculator and EV vs petrol car calculator.

Common mistakes when using carbon intensity

• Mixing CO₂ and CO₂e. Direct combustion factors usually count CO₂ only. Life-cycle factors count CO₂-equivalent, including methane and nitrous oxide. Don’t compare a CO₂-only figure for one country with a CO₂e life-cycle figure for another.
• Using an old year. Grids change fast. A decade ago the UK’s or Germany’s intensity was 40–60% higher than today, so a 2015 factor overstates current emissions.
• Ignoring losses. Factors at the power station exclude transmission and distribution losses. If you want emissions per kWh at the meter, add 5–10%.
• Applying a national average to a self-generating site. Rooftop solar you use on site never touches the grid. Multiply only net imports by the grid factor.
• Treating marginal and average as interchangeable. Calling a new load “clean” because the grid average is low is as simplistic as calling it “dirty” because coal sets the margin. Say which figure you use and why.
• Forgetting the direction of travel. For long-lived assets like heat pumps and EVs, what counts is the average over the next 10–20 years, and in most countries that will be well below today’s figure. Projections from national grid operators or IEA scenarios give a reasonable range.
• Double counting renewables. If a supplier sells you certificates from a wind farm, that generation should come out of the residual mix used for everyone else. Some countries publish a “residual mix” factor for exactly this reason.

Green tariffs and market-based accounting

Under the GHG Protocol, companies report scope 2 emissions two ways: location-based (grid average) and market-based (reflecting contracts such as renewable energy certificates, Guarantees of Origin and PPAs). Certificates draw criticism because buying them rarely pays for new generation. Europe’s large surplus of Norwegian hydro certificates has kept their price very low for years. Stricter approaches include:

• Additionality: contracts tied to new projects that would not otherwise be built.
• 24/7 hourly matching: matching consumption with clean generation in the same hour and grid region. Several large technology companies have adopted it as a goal, and it is part of the GHG Protocol’s revision discussions.
• Emissionality: building new projects where they displace the most fossil generation.

At home, the surest ways to shrink your electricity footprint are to use less, shift use to cleaner hours and make your own power. The solar panel calculator estimates rooftop output.

Bottom line

Grid carbon intensity is the number that decides what electrification achieves. It tells you how much an EV, a heat pump or a data centre actually emits. Values run from under 50 g/kWh on hydro- and nuclear-dominated grids to around 700 g on coal-dominated ones, and the world average of about 460 g is falling as solar and wind grow. Use the annual average for footprints, hourly signals for timing, and marginal figures to judge interventions. Then check how your country compares on the rankings and work out your total footprint with the carbon footprint calculator.

Figures in this guide are typical ranges drawn from the sources above; your own numbers depend on location, prices and equipment. Use the linked calculators for site-specific estimates.