What is Power Usage Effectiveness and How It Impacts Your Costs

By: Blair Felter on February 28, 2020

According to some estimates, the world’s data centers are expected to consume as much as eight percent of all power generated around the globe by 2030. With the adoption of cloud computing and wireless Internet of Things (IoT) devices showing no signs of slowing, the future is all but guaranteed to be more data and technology-intensive. The digital transformation of global markets will continue to drive the demand for more data centers, which is why these facilities will consume more power in the future.

Fortunately, innovations in data center technology have also been accompanied by breakthroughs in energy efficiency. Today’s data centers are much more efficient than their predecessors, as evidenced by the newfound emphasis on an important efficiency metric known as power usage effectiveness (PUE).

What is Power Usage Effectiveness?

Data centers obviously consume massive amounts of energy, but the majority of that energy is dedicated to powering and cooling the IT equipment housed within their walls. In that sense, data center power consumption delivers clear benefits that offset the enormous energy costs. If a facility is using more power than is necessary to power its IT infrastructure, however, it provides less value than it should and represents a wasteful drain on limited energy resources.

Over the last decade, the data center industry has widely adopted the power usage effectiveness rating as a way of evaluating data center efficiency. Quite simply, a data center with a high PUE score is consuming more energy than it should and is therefore less efficient. If a facility has a low PUE score, its total power usage is much closer to the energy demands of its IT equipment, which means it is more efficient.

When calculating the power usage of IT equipment, it’s important to remember that this figure should include more than just the servers running on the data floor. It also accounts for the facility’s cooling infrastructure and environmental controls. If these systems have to work overtime to regulate the temperature of servers, then the facility’s PUE score will suffer. Conversely, if the servers require less cooling than would be expected, the PUE score will drop accordingly.

How Do You Calculate a Data Center’s Power Usage Effectiveness?

The calculation for PUE is actually quite straightforward, which is why this metric has proven so useful and why data centers find it so easy to explain. A facility’s power usage effectiveness is equal to the total amount of power it consumes divided by the energy used by its IT equipment:

PUE = Total Power Consumption / IT Energy Needs

A perfect score of 1.0 would mean that every kW of energy used by the facility went toward the data center’s IT equipment. For example, a facility that consumed a total of 15 MWh of electricity with IT equipment requiring 11 MWh of power would have a PUE score of 1.36.

This score would actually place a facility in very good standing compared to the rest of the industry. According to data gathered from around the world each year by the Uptime Institute, the average data center PUE in 2019 was 1.67. While this average is clearly an improvement from when the Uptime Institute first provided this data in 2007 (when the average data center PUE was 2.5), it actually represents a slight increase from the record 2018 average data center PUE of 1.58. In fact, 2019 marked the first such increase since 2007.

Why is Power Usage Effectiveness Important?

There are a few reasons why organizations should care about PUE. From a big picture standpoint, having more energy-efficient data centers helps to offset the overall rising energy costs of the world’s computer technology infrastructure. As new technologies are developed and expand into new markets, data and power demands will continue to escalate. Controlling these costs through energy-efficient best practices will help make rapid growth more sustainable and enduring.

From a small-scale perspective, energy-efficient data centers deliver cost savings directly to their customers. One of the reasons why so many organizations have turned from outdated private data centers to state-of-the-art colocation facilities is that older in-house solutions were incredibly inefficient and expensive. Companies grew tired of paying higher energy costs without a corresponding increase in IT performance. Colocation data centers with low PUE scores deliver better value to their customers because they’re not forced to pay for the facility’s wasteful energy practices.

How to Reduce PUE in Your Data Center

While PUE is conceptually simple, it actually represents a rather complex interplay between a data center’s infrastructure and the computing assets within it. Colocation customers can directly impact a facility’s PUE by adopting energy-efficient practices for their IT deployment. Server sprawl, disorganized cabling, and poor server placement can all impact power distribution and cooling efficiency, which are two of the most important factors in determining PUE performance. Organizations need to work with their colocation provider to make sure they are right-sizing their deployment to avoid wasting energy and passing those costs along to fellow colocation customers in the form of higher cooling bills.

Virtualization technology has also had a major impact on PUE scores. Although the high-density servers that host virtual machine instances consume more power than a typical server, their ability to host multiple software-defined servers makes it possible to eliminate several physical servers. On balance, virtualization enables data centers to host more clients on fewer actual machines, which helps to drive energy costs down.

As more organizations undergo digital transformation and increasingly rely upon technology to deliver their products and services, the demand for data centers is unlikely to decline anytime soon. With global temperatures and fossil fuel consumption placing very real constraints upon global economic growth in the 21st century, it is more important than ever for organizations to emphasize data center power efficiency . By adopting a few key best practices, every data center customer can contribute to that effort while helping to control their colocation costs at the same time.

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