The Internet abounds with information on the topic of thermal output.

I’ve collected the following formulas and placed them here for my quick reference.

 Watts = 0.293 * BTU-Hr Watts = 3,530 * Tons BTU-Hr = 3.41 * Watts Tons = 0.000283 * Watts

For example,

• PacketLight PL-1000TN Optical Transport Unit PSU rated at 70 watts is
`238.7 BTU-Hr = 3.41 * 70 watts`
• HP ProLiant DL120 Generation 7 (G7) PSU rated at 570 watts is
`1943.7 BTU-Hr = 3.41 * 570 watts`
• Dell PowerEdge R410 Rack Server with Non-Redundant PSU rated at 480 watts is
`1636.8 BTU-Hr = 3.41 * 480 watts`

Volts will change the wattage; consider the following calculation.

`Power (watts) = Voltage (volts) * Current (amperes)`

If you are looking for information on sizing the thermal footprint of a datacenter there are other factors to take into consideration in addition to server and network equipment.

For example,

• People (see note 1)
• Lighting
• Powered devices (non-IT gear)
• Windows (sun light)
• Heat conduction via exterior (outside) facing walls
• Raised/non-raised floor
• Humidity

When I set out to research the formula for determining a system’s thermal output I found myself caught up in the additional information I came across.  To me that’s like finding \$5 bill in my pocket.

Note 1
There is general agreement that the human body will produce ~100 watts.  The following link has a brief discussion on the topic – interesting I thought.
http://hypertextbook.com/facts/2003/WeiLiangMok.shtml