How much cooling does a server room need?

The cooling capacity must equal the total heat output plus a safety margin. All electrical energy consumed by IT equipment becomes heat — a server drawing 1 kW produces 1 kW of heat. Add UPS losses (5-10%), lighting, and a 20% safety margin. A typical small server room with 5 kW IT load needs approximately 6-7 kW of cooling.

What temperature should a server room be?

ASHRAE TC 9.9 recommends 18-27°C (A1 class servers), with a target of 22-24°C. The previous standard of 20-22°C is now considered unnecessarily cold, wasting energy. Relative humidity should be 20-80% (non-condensing). Hot aisle temperatures of 35°C+ are acceptable with proper containment.

What is N+1 redundancy for server room cooling?

N+1 means installing one extra cooling unit beyond what is needed (N). If you need 3 units to handle the heat load, install 4. This ensures cooling continues if one unit fails, preventing overheating and equipment damage. Critical data centres may use N+2 or 2N redundancy for higher reliability.

Should I use split AC or precision cooling?

Standard split AC units are suitable for small comms rooms (under 10 kW heat load) where precise temperature control is not critical. Precision (close-control) AC units maintain tighter temperature and humidity control, have higher sensible heat ratios (no wasted latent cooling), and are designed for 24/7 operation. Use precision cooling for loads above 10 kW.

How do I account for UPS heat loss?

A UPS with 95% efficiency wastes 5% of the IT load as heat. For a 10 kW IT load, the UPS adds 0.5 kW of heat. Include this in the cooling calculation. Also account for power distribution losses (~2-3%). Online double-conversion UPS units are typically 94-97% efficient; line-interactive units are 97-99% efficient.

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Server Room Cooling Calculator — IT Heat Load

Calculate cooling capacity for server rooms and comms rooms from IT equipment heat output. Includes UPS losses, safety margins, and N+1 redundancy per ASHRAE guidelines.

IT Equipment Load

Total power draw from all IT equipment

Cooling Type

Room Length

Room Width

Target Temperature

ASHRAE: 18-27°C recommended

N+1 Redundancy

Extra unit for fault tolerance

How We Calculate This

This calculator determines the cooling capacity needed for a server room or comms room based on the total heat output from IT equipment and ancillary systems.

Heat load calculation

IT equipment: 1 kW electrical input = 1 kW heat output
UPS losses: (1 - efficiency) × IT load
Lighting: All energy becomes heat
Safety margin: Typically 1.2× (20%)

Design parameters

The cooling system must remove the total heat load while maintaining 18-27°C per ASHRAE TC 9.9. Airflow is calculated assuming a 10°C temperature rise across the cooling coil. N+1 redundancy ensures continued cooling during maintenance or unit failure.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.