Where does all the power go?

Electrical power generally originates from a machine that turns water into steam to turn turbines (or HEP, Gas Turbine) - in all cases some form of original energy is used to drive a generator set. Typical coal, nuclear or oil fired power stations generate steam to drive the generators. Typically these are only 30% efficient - that is 70% of the input energy is exhaused to the atmosphere, 30% to electricity.

Once the power is generated, it needs to get into the power distribution system. Power distribution is where power is transmitted along high voltage lines via transformers to the end destination. Ohms Law kicks in here V=IR, the larger the voltage the lower the current on the same transmission system. High currents cause power loss (I²R). Even so up to 2% of the transmitted power is lost in the grid.

At the data centre power is fed in via step down transformers and through switches into rectification circuits. Rectification converts the AC into DC so that batteries can be charged. The batteries are used to provide power during brown outs or power loss and before the backup generator sets kick in. The batteries power Uninterruptible Power Supplies (UPS) that convert the DC back into AC to provide power into the data centre hall. AC is fed via Power Distribution Units (PDU) into the data centre cabinets and then into the servers, storage systems and network systems. These systems have internally mounted power units that convert from AC into DC that is used to drive the processors, memory units and disks.

So in summary, AC comes into the data centre, gets converted to DC, gets converted to AC, gets converted to DC. Wild huh?