Optimizing PUE: Cut Data Center Costs & Boost Efficiency

Importance of PUE on Data Center Costs

Efficiency measurements like Power Usage Effectiveness (PUE) play a crucial role in assisting data center owners and operators in identifying areas for improvement. PUE not only helps in evaluating a data center’s environmental impact and carbon footprint but also aids in identifying cost-saving measures. In this article, we will explore the significance of PUE, how to calculate it, and techniques to lower it for improved data center performance and reduced operating costs.

What is Power Usage Effectiveness (PUE)?

Power Usage Effectiveness (PUE) is a metric used to assess a data center’s energy efficiency. A lower PUE indicates a more efficient data center. PUE is critical in identifying the environmental impact and energy efficiency of a data center.

Understanding the PUE Formula: Step-by-Step Breakdown

To fully grasp how PUE impacts data center operations, it’s important to understand how it is calculated. The formula for Power Usage Effectiveness is:

PUE = Total Facility Energy / IT Equipment Energy

Total Facility Energy: This is the total amount of energy consumed by the data center, including power used for IT equipment, cooling systems, lighting, UPS losses, power distribution, and other infrastructure.
IT Equipment Energy: This refers only to the energy used directly by servers, storage devices, networking hardware, and other computing systems.

Step-by-Step PUE Example

Let’s walk through a simple calculation:

Measure Total Facility Energy:
Suppose your data center consumes 1,000,000 kWh over a given period.
Measure IT Equipment Energy:
During that same period, the energy used by servers and IT hardware totals 600,000 kWh.
Calculate PUE:
$PUE = 600 , 000 kWh / 1 , 000 , 000 kWh = 1.67$

Interpretation

A PUE of 1.67 means that for every 1 watt used by IT equipment, 0.67 watts are used by supporting infrastructure. The ideal PUE is 1.0, indicating that all energy is used exclusively for IT equipment. an extremely rare scenario in real-world facilities.

Key Takeaway

Tracking your PUE regularly helps identify inefficiencies in cooling, power delivery, and other non-IT energy consumption. By targeting these areas, you can reduce operational costs and improve sustainability.

Use the interactive calculator below to calculate your own PuE.

PUE Calculator Widget

As of 2024, Power Usage Effectiveness (PUE) remains a core metric for assessing data center energy efficiency. The latest figures from the Uptime Institute’s 2024 Global Data Center Survey report that the industry-wide average PUE is now 1.56, a marginal improvement from 1.58 in 2023.

🔍 Key Insights from the 2024 Report:

The average annual PUE of 1.56 reflects a continuing trend of stagnation, with most gains from low-cost optimizations (e.g., blanking panels, VFDs, higher temp set points) already realized.
Nearly 47% of facilities are over 11 years old, limiting their ability to adopt newer energy-saving technologies.
New data center builds are consistently reporting PUEs of 1.3 or better, but their impact on global averages is still diluted by legacy infrastructure.
The report emphasizes that further efficiency gains will likely come from IT densification and innovations in direct liquid cooling and next-generation facility design.

This data underscores the importance of not just tracking PUE, but also investing in infrastructure modernization to achieve meaningful gains. While the industry awaits a “step change” in efficiency, forward-thinking operators are already achieving lower PUEs through strategic upgrades and holistic design approaches.

Real-World Examples of PUE Optimization in Action

To better understand how PUE improvements translate into real-world benefits, here are a few notable case studies from data centers that have successfully reduced their Power Usage Effectiveness through strategic upgrades and design choices:

Google – St. Ghislain Data Center, Belgium

Google has long been a leader in sustainable data center operations. At its St. Ghislain facility, the company implemented industrial-scale free cooling using water from a nearby industrial canal. By eliminating the need for mechanical chillers, they significantly reduced energy used for cooling and achieved a PUE as low as 1.11. This innovation not only saved operational costs but also dramatically lowered environmental impact.

Facebook – Luleå Data Center, Sweden

Located near the Arctic Circle, Facebook’s Luleå facility uses the naturally cold climate for air-side free cooling and a custom-designed electrical system to minimize energy loss. These strategies helped achieve a PUE of approximately 1.07, positioning it among the most efficient hyperscale data centers in the world.

National Australia Bank (NAB) – Melbourne

In Australia, NAB modernized their on-premises data center by retrofitting their legacy HVAC systems with in-row cooling, hot aisle containment, and variable speed fans. These measures helped reduce the facility’s PUE from 2.0 to 1.4, resulting in a 30% drop in energy costs and a faster ROI than originally projected.

What These Cases Teach Us

These examples demonstrate that improving PUE isn’t limited to hyperscalers. Whether it’s a multinational tech firm or a local enterprise, targeted energy efficiency strategies — such as free cooling, containment systems, or equipment upgrades — can drive substantial operational savings and sustainability gains.

How Can Data Centers Lower Their PUE?

There are several effective techniques to reduce PUE and enhance energy efficiency in data centers:

Temperature Optimization: Raising the temperature within the facility to the recommended levels by ASHRAE can significantly improve energy efficiency without harming IT equipment. Read – What Temperature Should my Data Center be?
Aisle Containment: Implementing hot or cold aisle containment prevents the mixing of hot and cold air, improving cooling efficiency and reducing energy consumption. Read – Data Center Containment Myths
Free Cooling: Leveraging free cooling in colder regions can reduce reliance on energy-hungry cooling systems and contribute to substantial energy savings.
Electricity Distribution: Utilizing high-efficiency UPS systems and eliminating unnecessary voltage converter stages reduces power loss and cooling load, resulting in cost savings.

Drawbacks in Measuring The PUE?

While PUE is a valuable tool for data center facilities departments, it can sometimes lead to unintended consequences. Lowering PUE without strategic planning may result in reduced availability and unanticipated outcomes. Therefore, data center administrators must carefully consider the impact of changes to ensure they align with energy efficiency goals. Some drawbacks to focusing too much on PUE are enumerated below.

Focus on Power, not Performance: PUE primarily measures the efficiency of the data center’s power usage. It does not provide insight into the overall performance of the data center, such as its computational efficiency, the effectiveness of cooling systems, or other critical factors that impact the data center’s functionality.
Doesn’t Account for Different Workloads: PUE treats all data centers as if they have the same workloads, regardless of their specific applications or IT equipment. In reality, data centers can vary significantly in terms of the type and intensity of workloads they support.
Variation in Climate and Location: PUE does not take into account the geographical location of data centers and the local climate conditions. Data centers in different regions may require varying levels of cooling, which can significantly affect their overall efficiency.
Limited Scope: PUE only measures energy efficiency within the data center facility itself and does not account for the energy consumed by the IT equipment or other infrastructure components outside the data center building, such as network and storage.
No Consideration of Redundancy: PUE does not account for redundancy levels within a data center. Data centers with higher redundancy levels (e.g., N+1 or 2N) may have higher energy consumption due to redundant systems, but PUE does not differentiate between them.
Lack of Industry Standardization: While PUE is widely used, there is no universal standard for calculating it. Different organizations may calculate PUE differently, leading to inconsistencies in reported values.
Seasonal and Dynamic Changes: PUE values can vary throughout the year and even throughout the day, depending on factors like outside temperature, IT load, and the efficiency of cooling systems. Static PUE measurements may not capture these fluctuations.
Focus on Energy, not Environmental Impact: PUE is primarily an energy efficiency metric and does not consider other environmental impacts such as water usage, e-waste, or the source of energy (e.g., renewable vs. non-renewable).
Ignores IT Equipment Efficiency: PUE doesn’t account for the energy efficiency of the IT equipment itself, which is a significant contributor to a data center’s overall energy consumption.
May Encourage “Greenwashing”: Some data centers may focus solely on improving their PUE without making substantial improvements in other areas of environmental sustainability. This can lead to a superficial emphasis on energy efficiency while neglecting other important aspects of responsible data center operation.

While PUE is a valuable tool for assessing the energy efficiency of data centers, it should be used in conjunction with other metrics such as WUE to provide a more comprehensive view of data center performance and sustainability.

Cascade Effect of Other Metrics?

To achieve substantial energy savings, it’s crucial to focus on reducing the IT load itself. Lowering the IT load has a multiplier effect, positively impacting power system losses and support infrastructure power requirements. Understanding the “cascade effect” of reducing the IT load can lead to significant overall energy savings.

AKCP Online PUE Calculator

Not sure what your PUE is, or want to benchmark your performance? Checkout our free online PUE calculator tool.

But how do you go about making these savings and implementing the changes in your data center that are required? AKCP has a wide range of sensors for your data center including cabinet thermal maps and differential air pressure sensors. These sensors allow you to make changes in your data center and with AKCPro Server see in real-time the effect it has on your PUE. You can ensure that your data center is running at optimal condition, without violating ASHRAE recommended rack inlet temperatures and ∆T as well as ∆P values.

Conclusion

Power Usage Effectiveness (PUE) is a crucial metric for evaluating data center energy efficiency and reducing operational costs. By adopting various techniques such as temperature optimization, aisle containment, and free cooling, data centers can significantly improve their PUE and overall energy efficiency. It’s also essential to consider the cascade effect of reducing the IT load, which can lead to substantial energy savings. To achieve these goals effectively, data center operators can rely on AKCP’s comprehensive ecosystem of products, including cabinet thermal maps, power monitoring sensors, and AKCPro Server, to track and optimize their energy usage and improve their PUE.