# BTU Calculation

The British Thermal Unit, or BTU, is an energy unit. It is approximately the energy needed to heat one pound of water for 1 Fahrenheit. 1 BTU = 1,055 joules. 1BTU/hour = 0.293 watt.

Formula for calculation: Watts = Volts x Amps

Power consumption

All power supplies, whether in desktops or servers, are on average approximately 60%-80% efficient. This implies that say a 200 watt maximum output PSU would consume 333 watts of input power to supply these 200 watts on full load.

Heat output

Heat output is measured in British Thermal Units (BTUs) – 1kw/hr = 3412 BTU/h or 1000 BTU/h is around 293W.

Based on the 754 watt figure, BTUs/hr = (754 watts * 3600) / 1054 = 2577 BTUs per hour, per server.

When calculating the amount of cooling (air conditioning) required in a room, you should take into account that the room should always be maintained at an ambient temperature of much less than 35 degree Celsius and that any other equipment in the room will also generate heat.

Example : For my server room we have

12500 watts of usage (that is max usage based on PS usage).

So 12,500 x 3.41 = 42,000 BTU/Hr.

One ton of capacity is 12,000 BTU/HR

so 42,000/12,000 == 3.5 Tons