Chapter 11 - Data Centers Overview

For many companies, data centers are major contributors to total operating costs and environmental impact. Data centers typically have been designed and operated with little consideration for energy efficiency. As a result, there are many efficiency opportunities with exceptionally strong business cases, as discussed below.

Data centers are critical to business

Businesses of all types have become increasingly dependent on information technologies (IT ). Most businesses rely on IT to manage core business functions, such as account management, web presence and sales, as well as finances, human resources and email systems.

IT computing equipment has evolved from mainframe machines used only for specialized functions to ubiquitous servers. Since critical business functions depend on computing capacity, 24-7 server availability, or “uptime,” is important. To maximize uptime and capture economies of scale, servers are commonly aggregated into data center facilities, also known as “server farms.” Data centers facilities are designed to supply high quality power to servers and keep equipment cool.

Some large companies own their own data centers, while others outsource their IT functions or lease data center space managed by a hosting company. Data centers that lease space are known as co-location centers, or “co-los.” It is also common for companies to set aside space in their office buildings for servers, commonly known as server closets.

Data centers are major energy users

Servers are major consumers of electricity. An individual server uses about 300 W of power, equivalent to three bright (100 W) incandescent light bulbs. Like an incandescent bulb, servers convert much of their energy to heat. However, since servers run constantly throughout the year, their energy use and heat production are much higher than any light bulb.

In many data centers, cooling systems and other infrastructure—power reliability equipment and lighting—use as much energy as the servers themselves. As a result, a single server with support systems has an annual footprint of more than five tons of carbon dioxide, the equivalent of a typical minivan driven 12,000 miles per year.1 Large data centers commonly house 10,000 or more servers. For many non-manufacturing companies, data centers are major contributors to the corporate environmental footprint.

Data centers have become significant power users in the United States. In 2006, the EPA estimated that 1.6% of electricity was consumed by data centers, a number projected to double by 2011.

A strong business case exists for making data centers more efficient

In a typical data center, less than 5% of the power consumed is used for computing operations. The other 95% is simply lost along the way—as heat in the servers, as conversion losses in power supplies, powering fans and lights, and in cooling systems required to remove all that waste heat.2

Efficiency opportunities exist at each step of the system. In many cases, best practices are well known, as described below. Because increased energy use drives increases in both operating costs (electricity) and capital costs (for back-up generators, battery banks and cooling systems), efficiency measures in data centers generally cut costs quite dramatically and pay back relatively quickly.

More specifically, efficiency measures provide economic value in three main ways:

  • Saving energy reduces electricity costs required to power and cool servers;
  • Energy efficiency increases the number of servers that can be supported by existing data center infrastructure, delaying or eliminating demand for expensive new data centers;
  • In new data centers, designing more efficient systems can substantially reduce total capital outlays.

IT hardware and software efficiency measures may reduce server energy use by 90%. When coupled with 40% efficiency potential in cooling system retrofits, an optimized data center system may reduce energy demand per computing operation by 92%.3

Of course, costs and savings from efficiency measures vary among data centers. The savings and cost numbers in the rest of this chapter are rough estimates; they will need to be verified in order to be applied to specific data centers.

Additional information

More information on data center energy use is available at:
• US EPA, “Report to Congress on Server and Data Center Energy Efficiency.” August 2, 2007. Accessible at

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