If a data center's PUE is 1.2 compared with 1.8, which indicates greater energy efficiency and why?

• A. 1.8 is more energy-efficient because higher PUE indicates better efficiency
• B. Both indicate the same efficiency
• C. PUE does not relate to energy efficiency
• D. 1.2 is more energy-efficient because a lower PUE indicates less energy waste

Answer: (D)

Lower PUE indicates better energy efficiency in a data center. PUE compares the total facility energy to the energy used by IT equipment. A PUE of 1.2 means the overall energy use is 1.2 times the IT energy, so only 0.2 times the IT energy is spent on overhead like cooling and power distribution. A PUE of 1.8 has overhead of 0.8 times the IT energy. So 1.2 delivers far less energy waste in the infrastructure relative to the IT load, making it more efficient overall. Remember, ideal is 1.0, and PUE assesses facility efficiency, not the efficiency of the IT gear itself.