To calculate Power Usage Effectiveness (PUE) in a datacenter, you need to measure two key values: Total Facility Power and IT Equipment Power. PUE is a metric used to determine the energy efficiency of a datacenter. Here’s a step-by-step guide to calculate it:
1. Understand the Formula
The formula for PUE is:
[
PUE = {Total Facility Power}/{IT Equipment Power}
]
- Total Facility Power: This is the total amount of power consumed by the entire datacenter, including IT equipment, cooling systems, lighting, power distribution losses, and all other overhead.
- IT Equipment Power: This is the power consumed by the IT hardware only, such as servers, storage systems, network devices, and any other computing equipment.
2. Measure Total Facility Power
- Use the power meter at the main electrical input to the datacenter to measure the total power consumption of the facility.
- This should include all energy used by IT equipment, cooling systems (CRAC units, chillers, etc.), UPS systems, lighting, security systems, and other ancillary infrastructure.
3. Measure IT Equipment Power
- Measure the power usage of all IT-specific devices within the datacenter.
- This can typically be done at the Power Distribution Unit (PDU) level or directly at the racks where servers, storage, and networking devices are located.
- Ensure to exclude non-IT devices like cooling systems, lighting, and auxiliary equipment.
4. Perform the Calculation
Divide the Total Facility Power by the IT Equipment Power:
[
PUE = {Total Facility Power (kWh)}/{IT Equipment Power (kWh)}
]
5. Conduct Regular Measurements
- PUE should be measured continuously or at regular intervals (e.g., daily, weekly, monthly) to understand energy trends.
- Use monitoring tools to collect real-time power consumption data and calculate PUE automatically.
6. Interpret the Results
- A PUE of 1.0 is considered perfect, meaning all power is used exclusively for IT equipment, with no overhead for cooling, lighting, or other systems. In reality, achieving 1.0 is nearly impossible.
- A typical datacenter PUE ranges from 1.5 to 2.5, while highly efficient datacenters may achieve PUE values below 1.2.
7. Tips for Improving PUE
- Optimize cooling systems (e.g., implement hot/cold aisle containment, raise server inlet temperatures).
- Use energy-efficient IT equipment and modern power supplies.
- Implement renewable energy sources.
- Leverage virtualization and containerization to consolidate workloads and reduce hardware usage.
- Regularly maintain cooling and power systems to prevent inefficiencies.
Example Calculation
- Total Facility Power: 1,000 kWh
- IT Equipment Power: 800 kWh
[
PUE = 1,000/800 = 1.25
]
This means for every 1.25 kWh consumed by the facility, 1 kWh is used by IT equipment, and 0.25 kWh is used for cooling, lighting, and other overhead.
By actively monitoring and improving PUE, you can reduce operational costs and enhance the sustainability of your datacenter.
