McPhearson says his primary driver for selecting the APC units was to save floor space, but he's benefiting from savings in chilled water, too. Electricity costs for the APC and Leibert systems are about the same.

"Our new room runs about $1,000 a month for chilled water. Our old room runs around $2,300 a month for chilled water," McPhearson says.

McPherson says Cimarex is taking other steps to improve the efficiency of its data center operations, including consolidating and virtualizing servers.

"I get a lot of budget pressure," McPhearson says. "Efficiency is very important to me because I have to make a good business case. I'm focused on my ongoing operating costs."

Jim Smith, vice president of engineering with data center operator Digital Realty Trust, says reducing capital expenses is as important as reducing operating expenses when it comes to green IT.

"If you can design more efficient data centers, you can reduce the operating budget and you can reduce the capital costs," Smith says. "We're huge proponents of that...The big money is going to be made in reducing capital expenses."

2. Electric utilities

IT operations come to a screeching halt without electricity; and in some parts of the world, the availability of reliable power is the main driver for improving the energy efficiency of corporate IT operations.

In London, Mumbai, Tokyo and New York City, data center operators can't get more power to their sites. If they want to add new servers, they need to retire older ones. They can't plan on data center expansion; instead, they need to eke the most amount of processing power out of the data centers they have.

"Data centers are reaching their capacity in electricity," says Simon Mingay, research vice president at Gartner. "As organizations go to more dense, power-consuming technologies like blade servers, data centers are reaching their limits...Squeezing more watts out of the data center is absolutely what CIOs care about."

The lack of available power from utilities is why corporate IT buyers are starting to look at new metrics such as performance per watt of servers and desktops. It's also why data center operators are consolidating facilities and driving up their watts per square foot.

"One in four data centers around the globe is going to have an outage due to power over a five-year horizon," predicts Brian Brouillette, vice president of data center services at HP. "As companies are in growth mode and they are figuring out how to consolidate data centers, the issue that everybody is talking about now is cost. But the availability of power is a close second."

Over the last 36 months, HP has consolidated 85 data centers down to six, two each in Austin, Texas, Houston and Atlanta. Key to HP's strategy was making sure the remaining six data centers are as energy efficient as possible.