Carbon Intensity Definition

France's electricity grid emits about 50 grams of CO2 per kilowatt-hour. Poland's emits about 700. Both countries are in the EU, use modern technology, and have competent engineers. The difference is almost entirely explained by one number: carbon intensity.

Carbon intensity measures CO2 emissions per unit of energy output, typically in grams of CO2 per kilowatt-hour (gCO2/kWh). It is the single most important metric for tracking electricity decarbonization. Lifecycle carbon intensity includes emissions from construction, fuel supply, and decommissioning, not just combustion. This is why even zero-combustion sources like solar and nuclear have nonzero lifecycle intensities (from manufacturing panels or mining uranium).

Rank the technologies. Approximate lifecycle carbon intensities (IPCC median estimates): coal 820, natural gas 490, solar PV 41, wind 11, nuclear 12, hydropower 24 gCO2/kWh.

Explain France vs. Poland. France generates about 70% of electricity from nuclear (12 gCO2/kWh). Poland generates about 70% from coal (820 gCO2/kWh). Weighted average grid intensity follows directly.

If a country switches 30% of its coal generation to natural gas, how much does grid carbon intensity drop?

Calculate the coal-to-gas shift. Replacing 30% of coal (820 g) with gas (490 g) saves 30% x (820 - 490) = 99 gCO2/kWh on the shifted portion. For a 100% coal grid starting at 820, the new intensity is 0.70 x 820 + 0.30 x 490 = 721 gCO2/kWh. A 12% reduction, meaningful but far from zero-carbon.

Carbon intensity connects fuel choices to climate outcomes, making it the metric that policy targets, grid operators track, and investors price.

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