The International Energy Agency forecasts that based on current and proposed policies, global power generation will grow about 15,000 TWh (about 60%) from 2017 to 2040. About 70% of additions will be supplied by natural gas, wind, and solar photovoltaics in nearly equal shares. But despite a drop from its current share from 38% to about 25%, coal will remain the largest source of power generation to 2040. By 2040, gas will follow closely behind at 22%. The evolution of the generation mix differs markedly by region.

—Copy and art by Sonal Patel, a POWER associate editor.