The energy industry is the totality of all of the industries involved in the production and sale of energy, including fuel extraction, manufacturing, refining and distribution. Modern society consumes large amounts of fuel, and the energy industry is a crucial part of the infrastructure and maintenance of society in almost all countries. In particular, the energy industry comprises: the petroleum industry, including oil companies, petroleum refiners, fuel transport and end-user sales at gas stations; the gas industry, including natural gas extraction, and coal gas manufacture, as well as distribution and sales; the electrical power industry, including electricity generation, electric power distribution and sales; the coal industry; the nuclear power industry; the renewable energy industry, comprising alternative energy and sustainable energy companies, including those involved in hydroelectric power, wind power, and solar power generation, and the manufacture, distribution and sale of alternative fuels; traditional energy industry based on the collection and distribution of firewood, the use of which, for cooking and heating, is particularly common in poorer countries. Production and consumption of energy resources is very important to the global economy. All economic activity requires energy resources, whether to manufacture goods, provide transportation, run computers and other machines. Widespread demand for energy may encourage competing energy utilities and the formation of retail energy markets.