Estimate server-rack power consumption, heat output, cooling requirements, amperage, kVA, circuit utilization and annual energy use. Enter a total IT load or build the rack from individual servers, switches, storage systems and other equipment.
Nearly all electrical power consumed by IT equipment eventually becomes heat inside the data-center environment. For practical rack-planning purposes, 1 watt of continuous IT load produces approximately 3.412 BTU per hour of heat.
A rack drawing 10 kW therefore produces approximately 34,121 BTU/hr of heat before accounting for additional room, UPS, lighting, people or other facility loads.
How would you like to calculate the rack load?
Rack Configuration
Enter Power Requirements
Enter the quantity and estimated operating wattage of each equipment type. Use measured or typical operating consumption when available rather than simply adding every power-supply nameplate rating.
Modern server power supplies often operate with a high power factor. Use measured equipment data when available.
A
Estimated Rack Requirements
10 kW IT Load
Estimated Heat Output
34,121 BTU/hr
≈ 2.84 tons of cooling
IT LOAD
10.00 kW
APPARENT POWER
10.53 kVA
ESTIMATED CURRENT
50.61 A
CIRCUIT UTILIZATION
84.4%
DESIGN LOAD + HEADROOM
12.00 kW
ANNUAL ENERGY
87,600 kWh
PDU / CIRCUIT LOAD 84.4%
Review circuit loading and continuous-load requirements for the applicable electrical installation.
HEAT CONVERSION
10,000 W × 3.412 = 34,121 BTU/hr
Rack Equipment
Equipment Power Breakdown
Conversion Reference
Rack Power & Cooling Formulas
Calculation
Formula
Example at 10 kW
Watts to BTU/hr
Watts × 3.412
≈ 34,121 BTU/hr
BTU/hr to Cooling Tons
BTU/hr ÷ 12,000
≈ 2.84 tons
kW to kVA
kW ÷ Power Factor
≈ 10.53 kVA at PF 0.95
Single-Phase Current
W ÷ (V × PF)
≈ 50.6 A at 208 V / PF 0.95
Three-Phase Current
W ÷ (√3 × V × PF)
≈ 29.2 A at 208 V / PF 0.95
Annual Energy
kW × 8,760 hours
87,600 kWh/year
Quick Reference
Common Rack Load Examples
5 kW RACK
≈ 17,061 BTU/hr ≈ 1.42 cooling tons
10 kW RACK
≈ 34,121 BTU/hr ≈ 2.84 cooling tons
20 kW RACK
≈ 68,243 BTU/hr ≈ 5.69 cooling tons
30 kW RACK
≈ 102,364 BTU/hr ≈ 8.53 cooling tons
Important Planning Note
Power-Supply Wattage Is Not the Same as Server Consumption
A server equipped with two 1,100-watt power supplies does not necessarily consume 2,200 watts. Redundant power supplies are sized to support the server's potential load and redundancy requirements, while actual power consumption depends on CPU utilization, memory, storage, accelerator cards, fans and system configuration.
For existing systems, measured consumption from a metered PDU, UPS, server management controller or power meter generally provides a better planning input than simply adding PSU nameplate ratings.
Thermal Planning
Rack Heat Load Is Only Part of Cooling Design
Converting IT wattage to BTU/hr estimates the heat generated by the rack itself. A complete room-level cooling calculation may also need to consider UPS losses, lighting, people, external heat transfer, other electrical equipment, airflow, redundancy requirements and environmental design conditions.
IT Equipment Servers, storage arrays, network switches and other rack-mounted electronics.
UPS Losses UPS and power-conversion equipment are not perfectly efficient and can add additional heat.
Room Loads Lighting, occupants and other equipment can contribute additional heat to the space.
Cooling Redundancy Production facilities may require cooling redundancy beyond the calculated steady-state load.
Rack Planning
Server Rack Power Planning Best Practices
Measure Real Loads Use metered PDU, UPS or server-management data when actual operating measurements are available.
Plan for Growth Maintain appropriate capacity for future servers, storage and networking equipment.
Balance Redundant Feeds Dual-corded equipment should be planned around the intended A/B power architecture and failure state.
Monitor Cooling Capacity Higher rack density increases both electrical demand and thermal-management requirements.
Use Qualified Electrical Design Final branch circuits, breakers, PDUs and facility wiring should be designed for the applicable equipment, electrical code and installation requirements.
Calculator Assumptions
Rack Power Calculator Limitations
Results are engineering-planning estimates and should not be used as a substitute for electrical or HVAC design. Actual current draw varies with equipment loading, power-supply efficiency, power factor, voltage, phase balance and installation details.
Three-phase calculations assume a balanced load. PDU and circuit calculations should also account for applicable continuous-load requirements, redundancy design, branch circuits and local electrical codes.
Tech Supply Direct can help identify compatible enterprise servers, processors, ECC memory, storage, network adapters, power supplies and related hardware for rack deployments, virtualization environments and infrastructure upgrades.
