Improving Power Usage effectiveness

Written By Nate Bruns

To improve Power Usage Effectiveness (PUE) in a data center, operators can decommission or consolidate a variety of non-IT infrastructure and underutilized assets that consume energy without directly supporting the compute load. Here's a breakdown of what else can be decommissioned to improve PUE:

Power Infrastructure

1. Redundant or Legacy UPS Systems

  • Old, oversized, or redundant Uninterruptible Power Supply systems run at low efficiency.

  • Consolidating or upgrading to modular, right-sized UPS systems reduces losses and cooling load.

2. Transformers and Power Distribution Units (PDUs)

  • Remove or consolidate unused transformers and PDUs, especially those with low utilization or inefficient conversion rates.

  • Newer systems offer better efficiency at partial loads.

3. Inactive Power Circuits

  • Abandoned or unused circuits still energize wiring and may cause phantom loads.

  • Decommissioning unused electrical runs reduces baseline power draw and simplifies troubleshooting.


Cooling Infrastructure

4. Underutilized CRAC/CRAH Units

  • Decommission air conditioning units in areas with decreased or migrated IT load.

  • Running too many units causes short-cycling and poor airflow dynamics.

5. Inefficient Legacy Cooling Systems

  • Replace or retire older chillers, compressors, or DX units with high energy demand and low efficiency.

  • Use modern, energy-efficient alternatives (e.g., economizers, liquid cooling, variable speed fans).

6. Overcooled Zones

  • Decommission fans or chillers supporting low-density or unused racks.

  • Adopt hot aisle/cold aisle containment to reduce unnecessary cooling.


IT and Network Infrastructure

7. Idle or Underutilized Servers ("Zombie Servers")

  • Servers that remain powered but don’t contribute to compute workloads are pure overhead.

  • Identify and decommission these to reduce both power draw and cooling requirements.

8. Legacy Network Switches and Storage Devices

  • Older equipment often consumes more power per unit of data processed.

  • Consolidate workloads onto newer, more efficient hardware.


Physical and Facility Infrastructure

9. Unused Racks or Server Cabinets

  • Empty racks still disrupt airflow and may require unnecessary cooling.

  • Removing or repurposing them allows for better airflow management and containment strategies.

10. Lighting Systems

  • Decommission outdated, always-on lighting.

  • Upgrade to occupancy-sensor-based, energy-efficient LED lighting.


Environmental and Support Systems

11. Old Humidifiers/Dehumidifiers

  • If humidity control systems are oversized, outdated, or no longer needed due to climate/environmental changes, remove or replace them.

12. Battery Rooms with HVAC

  • If battery systems are decommissioned, their dedicated HVAC units can be removed as well.



System - Decommissioning Benefit

Rectifiers & Batteries - Reduces conversion losses, lowers heat load

Legacy UPS - Improves efficiency, lowers idle power

Idle Servers - Cuts power & cooling needs

CRAC/CRAH Units - Lowers overcooling and fan power

Abandoned Cabling - Improves airflow, reduces fire risk

Unused PDUs & Circuits - Eliminates phantom loads

Empty Racks - Enhances airflow and containment


Improving PUE is about aligning infrastructure with actual IT load. Anything not directly contributing to compute, storage, or networking should be scrutinized. Strategic decommissioning, combined with infrastructure right-sizing and modernization, can yield substantial gains in energy efficiency.

Nate Bruns
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