China has passed the U.S. to become the world's biggest energy consumer, according to new data from the International Energy Agency, a milestone that reflects both China's decades-long burst of economic growth and its rapidly expanding clout as an industrial giant.

China's ascent marks "a new age in the history of energy," IEA chief economist Fatih Birol said in an interview. The country's surging appetite has transformed global energy markets and propped up prices of oil and coal in recent years, and its continued growth...