As the world strives to cut carbon emissions, electric power from renewables has emerged as a vital energy source. Yet transport and industry will still require combustible fuels for many purposes. Such needs could be met with hydrogen, which itself can be produced using renewable power. Hydrogen provides high-grade heat, helping to meet a range of energy needs that would be difficult to address through direct electrification. This could make hydrogen the missing link in the transformation of the global energy system.