Calculating Server Rack Wattage/BTU


My time studying electrical engineering in college has definitely come in handy for calculating server rack wattage. Below, are some example calculations that can give you an idea of what to expect. Note: these calculations are merely a demonstration.

Rack Solutions Rack-151

  • Width: EIA Standard 19″ Rack Rails
  • External Width: 23.6″ – 600mm
  • Height: 78.74″ – 2,000mm – Rack Units: 42U
  • Depths: 39.37″ & 41.34″
  • Racks in other dimensions are available.

Dimensions for Server Room

8.2” w X 5’ = Area of 41 Square Ft.

Current Server Rack= 77” Height, 21” W x 32” L = Area of 4.6 Square Ft.

Free Space- 36.4 Square Ft.

Proposed Server Rack = 78.74” Height, 23.6” W X 41.34” L = Area of 6.7 Square Ft.

Free Space- 34.3 Square Ft.

Server Rack

42U Server Rack Cabinet- $899.99

Fan tray with 6 Fans for RACK-151- $159.99

42U Vertical Cable Management bar- $59.99

Baying Kit- $29.99

Cage Nut Tool- $14.99

2U Filler Panels (10 Pack)- $34.99

4U Filler Panels (10 Pack)- $59.99

Total- $1483.93

Rack Mounted Cooling

Tripp Lite Rack-Mount Cooling Unit Air Conditioner, AC, 7,000 BTU (2.0kW), 120V, 8U, 5-15P Plug (SRCOOL7KRM) $747.69

Tripp Lite Exhaust Duct Kit for Rack Mount Cooling Unit SRCOOL7KDUCT $116.76

TRIPP LITE Remote-Control Cooling Management SNMP SRCOOL7KRM Rack Cooler (SRCOOLNET2) $267.79

Total- $1,179.45

With any server rack/data room, power consumption is an essential area that needs thorough research and planning. I will first explain some of the power units, equations, and definitions that will be involved during this task.


Watts (W)- Unit of power used to describe a rate of one joule per second of energy transfer.

Kilowatt (kW)- Unit of measure of 1,000 watts of electrical power.

Kilowatt Hours (kWh)- Power in kilowatts/time in hours- How much energy you are using if you kept a 1000w device running for an hour. For example, a 100w light bulb would take 10 hours to amount to 1 kWh of energy.


Watts (W) = Volts (V) x Amps (A)

1 Kilowatt (kW) = 1,000 Watts (W)

1 Kilowatt Hour (kWh) = 1,000-Watt Hours

Now, we would research the wattage of all components on the rack and add them together to determine the maximum power usage, as seen below.

Watt Total

NAS – 26.7w running/ 11.65w standby

ADT iHub – 10.5w

Meraki Wireless – 9.8w

Meraki Firewall – 10w

Edgewater Gateway – 32w

Toshiba Strata – 60w

ADT CCTV power supply – 10w

Arris Touchstone – 15w

Arris Touchstone – 15w

MSI Phone Server – 350w

Server – 460w

Monitor – 28w

Switch – 253w/307w

ADT Security – 100w

*Did not add the cooler, however, it would consume 1020w Max*

1434w total

Calculating Kilowatt Hours (kWh)

To calculate the monthly kilowatt/hour usage, the next task would be figuring out the average number of hours in a month. 24-hours X 30 days in a month = 720 hours in a month.

Next, we need to solve for kilowatts. Since the maximum power usage of these devices will be 1434w, we would divide 1434w by 1000 to get a 1.434kW.

To find kilowatts per hour, take your kilowatts and multiply by the hours of the time period. So, 1.434kW X 720 hours in a month would equal 1,032.45 kWh, which would be the amount of power the rack would use in a month.

Why is this Information Helpful?

Knowing how much wattage/kW your server rack/data room is using has many benefits. When it comes to a UPS (Uninterruptable Power Supply), its capacity (how much power the UPS can provide, measured in watts) needs to be enough to match the load (the combined power of all devices you are using). Keep in mind that going above your suggested capacity allows for future additional devices.

All of the devices that are consuming or generating power will produce heat as well, measured in BTU (British Thermal Unit). The heat produced by electronic devices is usually expressed in the number of BTU generated in an hour (BTU/hr).

1 watt (W) of power equals 3.41 BTU’s per hour (BTU/hr). So, 1,434 Watts=4,893.0104 BTUs per Hour.

Knowing this, you can make an educated decision on how you will cool your rack/data room. Having an adequate external or rack-mounted smart cooler in conjunction with your buildings HVAC system would be optimal as if one fails, the other will be there for redundancy.

Hopefully, this information helps and please correct me if I made a mistake. I will be calculating these measurements for my actual rack shortly so any guidance would be appreciated.

Categories: Hardware

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