What is a grid's fuel mix?

A fuel mix is the breakdown of where a grid's electricity comes from: what share is nuclear, gas, coal, hydro, wind, solar, and so on. It's the single most useful number for understanding a power system, because it tells you about cost, emissions, and vulnerability all at once. France's nuclear-heavy mix means stable, low-carbon power; a gas-heavy mix means prices that move with fuel markets; a coal-heavy mix means cheap power but high emissions and retirement pressure.

There's an important distinction nrgmap is careful about: a fuel mix can be measured by installed capacity (how much is built) or by generation (how much it actually produces). Because capacity factors differ so much, with nuclear running near-constantly and solar only when the sun shines, the two pictures can look quite different. The mixes on nrgmap's country and state pages are tracked installed capacity from our public-data catalog, a robust proxy for the shape of a grid.