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• Irregular heat load in the datacenter. This is exacerbated by poor planning for heat
management as the topology of the datacenter changes.
• Increasing power costs across the U.S.
• A tendency to overcool datacenters. The “flood-cooling impulse” leads datacenter
managers to overcool their datacenters by more than two and a half times what is
needed.

Figure 4-1 shows where datacenters are using electricity.

Calculating Your Cooling Needs
In this section, we’ll talk about how you can figure out how much cooling your system will
require. PART II
All the equipment in your server room generates heat. So does the lighting. And so do
the people working there. All these sources of heat contribute to the heat load of the server
room. Typically this number is expressed in British Thermal Units (BTUs) or kW. One
kilowatt is the same as 3412 BTUs.

NOTE Your server room equipment vendors should be able to tell you how much heat load each
piece of equipment generates.
In order for your air conditioner to cool a room, its output must be greater than the heat
load. Before buying any new cooling equipment, it’s important to figure out how much you
need. To determine the heat load, you must take into consideration a number of factors, not
just the heat load of your equipment. The following sections address these additional
considerations.

Room Size
The room itself requires cooling. To calculate the cooling needs of the room, use this formula:

Room Area BTU = Length (meters(m)) × Width (m) × 337

Where Data Centers Use Power Running servers
7% 4% UPS, transformer, and distribution losses
15% Lighting
Chilling water or compressing coolant to
cool air
50% Cooling servers
Humidifying and dehumidifying
7%
4% Wasted by mixing in the room
3%
10% Design and system inefficiencies
FIGURE 4-1 Datacenters can manage their power use more efficiently.