Aggregate is consolidating from 11 data centers and server rooms to just two data centers, and the company wants one of them to be LEED-certified. In addition to using alternative energy sources, such as wind and solar power for lighting, Aggregate is using a mix of Microsoft and VMware virtualization software to reduce its server count.

Aggregate has 350 or so servers and could potentially reduce that to about 60% of the current count, says CIO George Kelly.

Because going green can require up-front spending before long-term savings are realized, a successful green project requires a careful approach and executive sponsorship. "It's always a little difficult when you are starting this type of a process in a company that's not really been doing it yet," Young says. "We were successful in starting small and identifying initiatives that had low costs but obvious returns."

Small companies might be able to accomplish energy efficiency goals more quickly than large ones, Erickson notes. "In a large organization, it can be slog going, but a single project can have a big impact," she says.

Whatever a company's size, Carney of Citigroup urges collaboration between IT shops and facilities operations, which is key for measuring and restraining IT power use.