A typical PC for example consumes about 135 watts of power. A Datacenter with about a 1000 servers should typically take about 135 x 1000 Watts or 135 Kilowatts and that would only power the computers. This does not include the air-conditioning and lighting.
According to to a research paper sponsored by The California Energy Commission in a datacenter about 50% of the total energy consumed is by the servers and about 35% is used by the Air conditioners.
This article deals with building energy efficient Datacenters."