The extraction of aluminium from aluminium oxide is only economical using fused-salt electrolysis. The energy requirement in the form of electrical energy is between 13 and 15 kilowatt-hours per kilogram of aluminium. Electricity costs are a large part of the cost of aluminium production so the aluminium industry is always trying to purchase the electricity or produce it itself as cheaply as possible, primarily with hydroelectric power plants as well as with thermal power stations. Today, over 50 per cent of the electricity used worldwide is from hydroelectric power, about 30 per cent from coal-fired plants, about 5 per cent from nuclear plants and about 10 per cent form natural-gas power plants.
The extraction of primary aluminium accounts for about two per cent of the world"s power generation, with markedly different percentages in the individual countries. The importance of the aluminium industry in Norway, Iceland or even Venezuela is explained by the widespread use of hydroelectric power in these countries.