Building for Energy Efficiency—Are the Savings Worth the Investment?

April 24, 2012 5 Comments »
Building for Energy Efficiency—Are the Savings Worth the Investment?

Energy efficiency is a point of focus for many companies, particularly as their data centers consume increasing amounts of energy (and as energy prices rise). And in a slow economy, this situation naturally leads to the question of how to reduce expenses and thus increase profitability, but building an energy-efficient data center may incur a range of added costs. The question, then, is one of ROI (return on investment): is building for energy efficiency worth the cost?

The Answer to the Question: Maybe

Although we might call one data center “energy efficient” and another “energy inefficient,” these are really just relative terms. No facility is 100% efficient; rather, efficiency falls into a range. Every data center design, however, still leaves room for efficiency improvements. And at each end of the spectrum (very inefficient or very efficient), one can easily imagine design alterations that are either very much worth the cost, or the opposite. For instance, putting in a little more effort to arrange server racks in a manner that optimizes airflow and creates warm and cold aisles will no doubt provide a fast return on a minimal investment. On the other hand, for an already highly efficient design, investing heavily in a system or configuration to gain a miniscule improvement in energy efficiency can easily be a waste of money—at least in terms of ever receiving a return comparable to the investment.

For most data centers (which fall between these extremes), the question of ROI on building for energy efficiency is much less clear. The closer a company comes to one extreme or the other tends to clarify the matter, but in the middle range, the question must be answered case by case. In other words, building for energy efficiency may be worth it, depending on the particular situation.

The Middle of the Road: Energy Efficiency Best Practices

The above qualifications notwithstanding, in some sense building for energy efficiency is always worth it—as long as the design doesn’t go to the extreme. For many companies, this middle ground involves building a facility that conforms to tried-and-true measures that other companies have used successfully to improve efficiency in a manner that provides a return on the investment. These measures are often called best practices, and if you follow trends in data center design, you’ll probably recognize many of them. Here are a few that are generally recognized as worthwhile investments to reduce energy consumption and thus provide ROI over the long term (and in some cases the short term).

  • Hot aisle/cold aisle containment. Larger temperature differentials improve cooling efficiency, thus reducing power consumption. This measure requires little by way of infrastructure—it mostly requires careful planning of facility layout—and thus can provide a fast return on investment.
  • Free cooling. Although free cooling is not entirely free, it does avoid much of the operational expense of mechanical cooling methods. Many data centers (depending on the temperature and humidity requirements of their IT equipment) can use free cooling most of the year, if not year round, yielding tremendous savings and a fast return on investment. Furthermore, facilities designed to rely heavily on free cooling also have reduced infrastructure needs for mechanical cooling, potentially balancing the any investment in greater efficiency.
  • High-efficiency UPS systems. All power consumed by IT equipment will first go through some form of uninterruptible power supply. UPS inefficiency, therefore, can be a tremendous waste of energy (and thus money). Depending on the lifespan and maintenance requirements of a high-efficiency UPS, the investment in efficiency can thus quickly provide returns, especially if the efficiency improvement is more than a few percent.
  • Efficient servers. Although higher-efficiency IT equipment doesn’t help your PUE (it can actually hurt it), it nonetheless improves overall efficiency and reduces energy consumption. The question in this case, however, is greater efficiency relative to what? Servers sporting processors manufactured in a cutting-edge 22nm process may be worth the investment relative to those with processors built in 90nm, but the choice is seldom so black and white. In between is a range, and one choice may be better than another. Given, however, that the lifetime operational (energy) costs of a server now exceed its capital cost, choosing servers with greater efficiency is typically going to be the best bet—although some careful thought may be required to maximize the returns.
  • Virtualization. Virtualization software requires an investment, but virtualized infrastructure can often reduce the required hardware needed to achieve a certain capacity. It can thus decrease both operational costs in the long term, and it may balance capital cost adjustments from the start.
  • Automated lighting systems. If lights are left on in unoccupied rooms, you’re losing money. An automated lighting system can eliminate much of this loss by automatically shutting off lights when they are not needed. Although the energy savings may not be as dramatic as those of some other efficiency measures, this step can still provide a return on the infrastructure investment.
  • “Recycling” waste heat. A data center is more or less a big heater (although it does a little more than that). So why use energy to separately generate heat for nearby office spaces when the data center produces plenty? Depending on the situation, a data center may provide enough heat to eliminate any need for separate heat generation. The question is whether the necessary infrastructure is worth the investment—and that depends on a variety of factors.
  • Computational fluid dynamics (CFD) analysis. CFD enables “previewing” the temperature and airflow dynamics of a data center design. This information can be used to eliminate hot spots and other anomalies, thus reducing the cooling needs of a facility and saving money. The catch is that CFD can be expensive, but the potential returns are significant.

Choosing the Right Course of Action

Building for energy efficiency is worth the investment, but you can also go overboard and end up wasting money. The key is choosing the right combination of energy efficiency design elements to maximize the return on the investment—and this combination will vary from data center to data center. Differences in the size of the facility, the climate, the purpose (for instance, a cloud data center versus a colocation facility) and the characteristics of the surrounding campus can all affect design choices. In effect, then, building for energy efficiency may or may not be worth the investment, but building wisely for energy efficiency is always worth the investment. Industry best practices for efficiency are an excellent place to start, and most data center designs will benefit from at least a subset of these measures—particularly those such as the use of free cooling, hot aisle/cold aisle containment and virtualization.

As energy prices rise, the threshold for a worthwhile investment in efficiency also becomes more reachable. But the benefits of energy efficiency go beyond just financial returns. An efficient design also gives a company public relations points, and overall industry movement in the direction of greater efficiency helps hold off government agencies, which invariably have the itch to impose new regulations (which are almost always costly). Furthermore, energy efficiency is simply a matter of corporate responsibility—particularly when it costs little to nothing (or even provides a return) in the long term.

Photo courtesy of Brooks Elliot

About Jeff Clark

Jeff Clark is editor for the Data Center Journal. He holds a bachelor’s degree in physics from the University of Richmond, as well as master’s and doctorate degrees in electrical engineering from Virginia Tech. An author and aspiring renaissance man, his interests range from quantum mechanics and processor technology to drawing and philosophy.


  1. Adrian Franks April 25, 2012 at 12:23 pm -

    For those data centers that utilize a lot of transformers, purchasing energy effecient harmonic mitigating transformers is another proven way to decrease energy costs. HMT/EE transformers can decrease transformer heat loss by 7% – 9% (over standard or K-rated transformers) thereby significantly decreasing utility costs related to the transformer by as much as 60%.

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