GRID · FIELD GUIDE
How Clean Is Your Electricity? — Reading the Carbon Intensity of the Grid
Flick a switch and the electricity looks identical wherever you are — but the carbon behind it isn’t. A kilowatt-hour from a hydro dam, a wind farm or a nuclear plant carries almost no emissions; the same kilowatt-hour from a coal station carries a great deal. So how is ‘how clean the grid is’ actually measured, why does it swing so wildly from one country to the next, and what are you really seeing when the map paints the world from green to red?
Electricity is the great equaliser of modern life: the same socket, the same voltage, the same gentle hum whether you’re in Oslo or Johannesburg. But that uniformity hides an enormous difference. Behind the socket, the carbon cost of each unit of power swings by a factor of twenty or more from one country to the next — and unlike the electricity itself, that difference is invisible. Carbon intensity is how we make it visible.
Grams of CO₂ per kilowatt-hour
The measure is deliberately plain. Take all the greenhouse gas released to generate electricity over some period, divide by all the electricity generated, and you get grams of CO₂-equivalent per kilowatt-hour — gCO₂/kWh. A kilowatt-hour is a tangible amount: roughly a cycle of the washing machine, an evening of television, a few boils of the kettle. Attaching a carbon figure to it turns an abstract climate question into something you can feel. At 30 g, that load barely touched the atmosphere. At 600 g, it carried twenty times the burden — for exactly the same light, heat or charge.
The number describes the source, not the electricity. Electrons don’t remember where they came from, and a clean kilowatt-hour does the identical work to a dirty one. What carbon intensity captures is everything that had to happen upstream to put that kilowatt-hour on the wire.
Why some grids are green and others red
The whole story is the generation mix. Hydropower, wind, solar, nuclear and geothermal generate electricity with almost no carbon released in the act, so a grid built mostly on them sits very low — frequently under 50 g. Norway, running overwhelmingly on hydro, and France, with its large nuclear fleet, are the classic clean grids. At the other end, burning fossil fuel carries that fuel’s emissions straight onto the grid: natural gas is the lighter fossil option, but coal and oil are far heavier, dragging grids that depend on them past 600 g and, in the most coal-bound cases, considerably higher.
Most countries are a blend, so they land in the middle and move over time — downward as wind and solar are built and coal plants close, sometimes upward in a drought year when the hydro runs low and gas fills the gap. A country with big rivers or a committed nuclear programme starts clean almost by geography; one still leaning on coal stays high until that coal is genuinely replaced rather than merely promised.
Lifecycle, not just the chimney
A fair comparison has to count more than smokestacks, and these figures do. They are lifecycle estimates: they include the emissions of building the power station, manufacturing the turbines or panels, extracting and moving the fuel, and decommissioning at the end — not only what comes out of a chimney while the plant runs. That’s what keeps the scoring honest. A wind turbine emits nothing as it spins, but it isn’t entirely free once you count the steel and concrete that raised it; counting only combustion would unfairly flatter some sources and punish others. Lifecycle accounting puts hydro, nuclear, gas and coal on the same footing — which is why even a very clean grid shows a small non-zero number rather than an implausible perfect zero.
Live for Britain, an honest annual everywhere else
Here the map does something it’s careful to be transparent about. Britain’s grid operator, NESO, publishes the carbon intensity of the GB grid every half hour, openly licensed and free to reuse — so Great Britain is shown live, its colour shifting through the day as the wind picks up, the sun sets, and plants come on and off. It’s a forecast rather than a settled meter reading, so it’s badged est., and live countries carry a bright green outline to set them apart.
Almost nowhere else publishes the same thing freely and commercially. So for every other country the map shows the most recent full-year average from Ember — a real, measured figure, latest year available — rather than fabricate a live one. The United States (through the EIA) and Europe (through ENTSO-E) both publish suitable live data and are next to come online, slotting into the very same view. Until then, the honest choice is a clearly-labelled annual average, never a real-time number we couldn’t actually source. A global live feed for the whole world does exist commercially, but its free tier forbids commercial use — so rather than pay for a figure or break a licence, the rest of the map stays an honest yearly average.
How to read the map
Everything is shaded on one scale. Deep green is a very clean grid near zero; yellow and orange are the middle ground; red is a heavily fossil-based grid past 600 g. A country without reliable data stays grey rather than being guessed at — a blank is more honest than an invention. Then watch the badge, because it tells you how fresh the number is: a live country wears a green outline and shows the grid as it stands right now (marked est.), while every other country shows its latest annual average, badged as annual. The colour answers how clean; the badge answers how fresh. Read the two together and the map tells you, at a glance and without overclaiming, exactly how much carbon is behind the light in any country on Earth.
Frequently asked questions
What does carbon intensity of electricity actually mean?
It’s a simple ratio: how much greenhouse gas is released for each unit of electricity generated, written as grams of CO₂-equivalent per kilowatt-hour — gCO₂/kWh. A kilowatt-hour is roughly what it takes to run a washing-machine cycle or boil a few kettles. If the grid serving you is at 30 g, that load came with almost no emissions; at 600 g it came with twenty times as much. The number doesn’t describe the electricity itself — a kilowatt-hour is a kilowatt-hour — it describes what had to be burned, or not burned, to make it. That’s why the same appliance can be nearly carbon-free in one country and a real source of emissions in another.
Why is some electricity so much cleaner than the rest?
It comes down to the mix of power sources feeding the grid. Electricity from hydropower, wind, solar, nuclear and geothermal releases almost no carbon at the point of generation, so grids dominated by those sit very low — often under 50 g. Electricity from burning fossil fuels carries the emissions of that fuel: natural gas is the cleaner of the fossil options, but coal and oil are far heavier, which pushes their grids past 600 g and sometimes well beyond. Most countries run a blend, so their figure lands somewhere in between and shifts as cleaner sources are added or fossil plants are retired. A country blessed with big rivers or a strong nuclear fleet starts clean almost by geography; one still leaning on coal stays high until that coal is replaced.
Does this count only the power station, or the whole story?
These figures are lifecycle estimates, which is the more honest way to count. A lifecycle number includes not just the CO₂ coming out of a chimney while the plant runs, but the emissions from building the plant, manufacturing the panels or turbines, mining and transporting the fuel, and so on. That matters for fairness: a wind turbine emits nothing while spinning but isn’t entirely free once you count the steel and concrete, and counting only smokestacks would flatter some sources and penalise others. Lifecycle accounting puts every kind of generation on the same footing, which is why a solar-heavy grid still shows a small non-zero number rather than a perfect zero.
Why is only Great Britain live when the rest is a yearly average?
Because truly live, openly-licensed carbon data is rare. Britain’s grid operator, NESO, publishes the carbon intensity of the GB grid every half hour, free and openly licensed, so we show it live — updating through the day as wind rises and falls and as plants switch on and off. Very few operators publish anything comparable for free with permission to reuse it commercially. For every other country we therefore show the most recent full-year average from Ember, a real measured figure, rather than invent a live one. The United States and Europe both publish suitable live data and are next in line; until then, the honest move is an annual average clearly labelled as such, never a real-time number we couldn’t actually source.
How do I read the colours and the badges on the map?
The world is shaded on a single scale from green to red: deep green is a very clean grid near zero, yellows and oranges are the middle, and red is a heavily fossil-based grid past 600 g. A country with no reliable data stays grey rather than being guessed at. The crucial detail is the badge: a country drawn live — currently Great Britain — carries a bright green outline and its value is the grid right now, marked ‘est.’ because the operator’s figure is a forecast. Every other country’s value is its latest annual average, badged as annual so you’re never left wondering whether a number is a live reading or a yearly one. The colour tells you how clean; the badge tells you how fresh.
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