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The Greening of IT
4 How Companies Can Make a Difference for the Environment

connected to the higher 208V service. The reason is that they need more
power; using a higher voltage gives more power and also saves energy.
Higher voltage saves energy because the formula for electric losses due to
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transmission over a wire is I R, where I represents amps, and R is the fixed
resistance of the wire. Because watts = volts × amps, we can double the
power (watts) by doubling the volts or doubling the amps. However, dou-
bling the amps would increase the losses by four times. Thus, to transmit
electricity over long distances, the practice is to increase the voltage as much
as possible. In high-tension towers, the voltage is often as high as 120,000
volts, and even in the power lines outside our houses, the voltage is often
4,000 volts. That voltage drops to 110V for use in our houses to reduce dan-
ger of electrocution. As noted, 220V power is used only for electric ranges,
clothes dryers, and so on, although in Europe, the base power is 220V. One
easy way to reduce energy transmission losses at data centers is to use 220V
(208V) service. Higher input voltage results in more-efficient operation.
Most servers (just like our laptops or hair dryers) are capable of either 110V
or 220V service. Older data centers often have 110V power sources for
servers, but switching to 220V (208V) would provide significant savings.
ptg
This change in voltage at data centers to reduce energy use is mentioned in
several places throughout the book.

The Growing Significance of Green IT and
Green Data Centers

Much of the emphasis in the following chapters is on data centers because
they almost always represent the starting point for green IT initiatives for
companies. Data centers—the facilities that primarily contain electronic
equipment used for data processing, data storage, and communications net-
working—have become common and essential to the functioning of business,
communications, academic, and governmental systems. Data centers have
been growing and expanding quickly as our economy continues to shift from
paper-based to digital information management. The U.S. EPA’s 2007
“Report to Congress on Server and Data Center Energy Efficiency” estimated
that the energy use of the nation’s servers and data centers doubled from
2000 to 2006 to approximately 61 billion KWH. Under current efficiency
trends, national energy consumption by servers and data centers could nearly
double again by 2011 to more than 100 billion KWH, representing a $7.4
billion annual electricity cost.