US data centers consumed about 70 billion kilowatt-hours of electricity in 2014, the most recent year examined, representing 2 percent of the country’s total energy consumption, according to the study. That’s equivalent to the amount consumed by about 6.4 million average American homes that year. This is a 4 percent increase in total data center energy consumption from 2010 to 2014, and a huge change from the preceding five years, during which total US data center energy consumption grew by 24 percent, and an even bigger change from the first half of last decade, when their energy consumption grew nearly 90 percent.

Efficiency improvements have played an enormous role in taming the growth rate of the data center industry’s energy consumption. Without these improvements, staying at the efficiency levels of 2010, data centers would have consumed close to 40 billion kWh more than they did in 2014 to do the same amount of work, according to the study, conducted by the US Department of Energy in collaboration with researchers from Stanford University, Northwestern University, and Carnegie Mellon University.

Energy efficiency improvements will have saved 620 billion kWh between 2010 and 2020, the study forecasts. The researchers expect total US data center energy consumption to grow by 4 percent between now and 2020 – they predict the same growth rate over the next five years as it was over the last five years – reaching about 73 billion kWh.

This chart shows past and projected growth rate of total US data center energy use from 2000 until 2020. It also illustrates how much faster data center energy use would grow if the industry, hypothetically, did not make any further efficiency improvements after 2010. (Source: US Department of Energy, Lawrence Berkeley National Laboratory)

Counting Electrons

Somewhere around the turn of the century, data center energy consumption started attracting a lot of public attention. The internet was developing fast, and many started asking questions about the role it was playing in the overall picture of the country’s energy use.

Many, including public officials, started ringing alarm bells, worried that continuing to power growth of the internet would soon become a big problem. These worries were stoked further by the coal lobby, which funded pseudo-scientific research by “experts” with questionable motives, who said the internet’s power consumption was out of control, and if the society wanted it to continue growing, it wouldn’t be wise to continue shutting down coal-burning power plants.

The DOE’s first attempt to quantify just how much energy data centers were consuming, whose results were published in a 2008 report to Congress, was a response to those rising concerns. It showed that yes, this infrastructure was consuming a lot of energy, and that its energy use was growing quickly, but the problem wasn’t nearly as big as those studies of murky origins had suggested.

“The last [DOE] study … was really the first time data center energy use for the entire country was quantified in some way,” Arman Shehabi, research scientist at the DOE’s Lawrence Berkeley National Laboratory and one of the new study’s lead autors, said in an interview with Data Center Knowledge.

What authors of both the 2008 report and this year’s report did not anticipate was how much the growth curve of the industry’s total energy use would flatten between then and now. This was the biggest surprise for Shehabi and his colleagues when analyzing the most recent data.

“It’s slowed down, and right now the rate of increase is fairly steady,” he said. “There’s more activity occurring, but that activity is happening in more efficient data centers.”

See also: Cleaning Up Data Center Power is Dirty Work

Fewer Servers

There’s a whole list of factors that contributed to flattening of the curve, but the most obvious one is that the amount of servers being deployed in data centers is simply not growing as quickly as it used to. Servers have gotten a lot more powerful and efficient, and the industry has figured out ways to utilize more of each server’s total capacity, thanks primarily to server virtualization, which enables a single physical server to host many virtual ones.

Each year between 2000 and 2005, companies bought 15 percent more servers on average than the previous year, the study says, citing server shipment estimates by the market research firm IDC. The total number of servers deployed in data centers just about doubled in those five years.

Growth rate in annual server shipments dropped to 5 percent over the second half of the decade, due in part to the 2008 market crash but also to server virtualization, which emerged during that period. Annual shipment growth dropped to 3 percent since 2010, and the researchers expect it to remain there until at least 2020.

The Hyperscale Factor

The end of the last decade and beginning of the current one also saw the rise of hyperscale data centers, the enormous facilities designed for maximum efficiency from the ground up. These are built by cloud and internet giants, such as Google, Facebook, Microsoft, and Amazon, as well as data center providers, companies that specialize in designing and building data centers and leasing them to others.

According to the DOE study, most of the servers that have been responsible for that 3 percent annual increase in shipments have been going into hyperscale data centers. The cloud giants have created a science out of maximizing server utilization and data center efficiency, contributing in a big way to the slow-down of the industry’s overall energy use, while data center providers have made improvements in efficiency of their facilities infrastructure, the power and cooling equipment that supports their clients’ IT gear. Both of these groups of data center operators are well-incentivized to improve efficiency, since it has direct impact on their bottom lines.

The amount of applications companies deployed in the cloud or in data center provider facilities started growing as well. A recent survey by the Uptime Institute found that while enterprise-owned data centers host 71 percent of enterprise IT assets today, 20 percent is hosted by data center providers, and the remaining 9 percent is hosted in the cloud.

This chart shows the portion of energy use attributed to data centers of various types over time. SP data centers are data centers operated by service providers, including both colocation and cloud service providers, while internal data centers are typical single-user enterprise data centers. (Source: US Department of Energy, Lawrence Berkeley National Laboratory)

Additionally, while companies are deploying fewer servers, the amount of power each server needs has not been growing as quickly as it used to. Server power requirements were increasing from 2000 to 2005 but have been relatively static since then, according to the DOE. Servers have gotten better at reducing power consumption when running idle or at low utilization, while the underlying data center power and cooling infrastructure has gotten more efficient. Storage devices and networking hardware have also seen significant efficiency improvements.

See also: After Break, Internet Giants Resume Data Center Spending

From IT Closet to Hyperscale Facilities

To put this new data in perspective, it’s important to understand the trajectory of the data center industry’s development. It was still a young field in 2007, when the first DOE study was published, Shehabi said. There was no need for data centers not too long ago, when instead of a data center there was a single server sitting next to somebody’s desk. They would soon add another server, and another, until they needed a separate room or a closet. Eventually, that footprint increased to a point where servers needed dedicated facilities.

All this happened very quickly, and the main concern of the first data center operators was keeping up with demand, not keeping the energy bill low. “Now that [data centers] are so large, they’re being designed from a point of view of looking at the whole system to find a way to make them as efficient and as productive as possible, and that process has led to a lot of the efficiencies that we’re seeing in this new report,” Shehabi said.

Efficiency Won’t Be the Final Answer

While the industry as a whole has managed to flatten the growth curve of its energy use, it’s important to keep in mind that a huge portion of all existing software still runs in highly inefficient data centers, the small enterprise IT facilities built a decade ago or earlier that support applications for hospitals, banks, insurance companies, and so on. “The lowest-hanging fruit will be trying to address efficiency of the really small data centers,” Shehabi said. “Even though they haven’t been growing very much … it’s still millions of servers that are out there, and those are just very inefficient.” Going forward, it will be important to find ways to either make those smaller data centers more efficient or to replace them with footprint in efficient hyperscale facilities.

See also: The Problem of Inefficient Cooling in Smaller Data Centers

As with the first data center study by the DOE, the new results are encouraging for the industry, but they don’t indicate that it has effectively addressed energy problems it is likely to face in the future. There are only a “couple of knobs you can turn” to improve efficiency – you can design more efficient facilities and improve server utilization – and operators of the world’s largest data centers have been turning them both, but demand for data center services is increasing, and there are no signs that it will be slowing down any time soon. “We can only get to 100 percent efficiency,” Shehabi said.

Writing in the report on the study, he and his colleagues warn that as information and communication technologies continue to evolve rapidly, it is likely that deployment of new systems and services is happening “without much consideration of energy impacts.” Unlike 15 years ago, however, the industry now has a lot more knowledge about deploying these systems efficiently. Waiting to identify specific efficient deployment plans can lead to setbacks in the future.

“The potential for data center services, especially from a global perspective, is still in a fairly nascent stage, and future demand could continue to increase after our current strategies to improve energy efficiency have been maximized. Understanding if and when this transition may occur and the ways in which data centers can minimize their costs and environmental impacts under such a scenario is an important direction for future research.”

Source: TheWHIR