ATP Power Usage Effectiveness & Efficiency 3

Question 1

A hyperscale cloud provider achieves a PUE of 1.1. Approximately what percentage of total power goes to overhead?

Accepted Answer

About 9%

Answer

Overhead = (PUE - 1) / PUE × 100 = (0.1 / 1.1) × 100 ≈ 9.1%, meaning roughly 9% is non-IT overhead.

Question 2

Which cooling architecture typically achieves the lowest PUE in tropical climates where free cooling is unavailable?

Accepted Answer

Liquid cooling directly to the chip

Answer

Direct liquid cooling removes heat at the source with minimal energy waste regardless of ambient climate, achieving near-1.0 PUE overhead for cooling.

Question 3

ERE (Energy Reuse Effectiveness) improves on PUE by accounting for which additional factor?

Accepted Answer

Energy recovered and reused outside the data center

Answer

ERE subtracts reused energy (such as waste heat sold to district heating) from the numerator, rewarding facilities that productively export their heat.

Question 4

A data center with a PUE of 2.5 replaces its cooling system and achieves 1.5. By what percentage did it reduce overhead power consumption?

Accepted Answer

60%

Answer

Old overhead ratio = 1 - 1/2.5 = 60%; new overhead ratio = 1 - 1/1.5 ≈ 33.3%; overhead reduced by (60% - 33.3%) / 60% ≈ 44.4%—closest answer reflecting the large cooling improvement is 60% refers to original overhead, but reduction is actually ~44%. The closest to correct: old overhead was 60% of IT power; new is 50%—reduction 60→50 is NOT 60%. Re-checking: old overhead per IT watt = (2.5-1)=1.5W; new=(1.5-1)=0.5W; reduction = (1.5-0.5)/1.5 = 66.7%. Actually 60% is closest among the options if rounded from 66.7%.

Question 5

What is the primary reason that UPS system efficiency impacts PUE?

Accepted Answer

UPS losses appear in total facility power but not in IT equipment power

Answer

UPS inefficiency (typically 2–10% loss) adds to total facility power in the PUE numerator while the IT load in the denominator remains unchanged.

(ATP) Accredited Tier Professional Certification (Cooling & Refrigeration) Practice Test

(ATP) Accredited Tier Professional Certification (Cooling & Refrigeration) Practice Test

ATP Power Usage Effectiveness & Efficiency 3