Worldwide electricity used by data centres doubled from
2000 to 2005, as shown in figure 1, representing an aggregate annual growth rate of 16.7% per year for the world. About 80% of this growth is attributable
to growth in electricity used by servers (almost entirely volume servers), with ten per cent of growth in electricity use associated with data centre communications and about the same percentage for storage equipment. The overall increase in server electricity use is driven almost entirely by the increase in the number of volume servers, with a small component associated with increases in the server power used per unit.