Data centers are a booming business, of course, as we report on all the time at GreenerComputing. With the rise of online shopping, telecommuting, virtual meetings, and the general spread of technology through everyday business activities, more and more companies are building or expanding their computing facilities.

But at the Fortune Brainstorm Green conference happening this week, Dell made the amazing revelation that, by waffling on their data center expansion plans, the company realized they might never need to build another new data center.

Robin Johnson, Dell's CIO, and Dane Parker, its Global Facilities Lead, took part in the virtual conference (you can attend it online through WebEx) yesterday to talk about how the greenest data center is the one you never build.

Dell surveyed its customer base about demand for new hardware and data center floor space, and found that 65 percent of its customers were out of space and considering new facilities. Despite being in the same position as their customers, Dell held off, a move Johnson described as a cost-mitigation play, buying a year's worth of time to think the decision through while renting out a colocation facility.

"The thing that happened in that year is that, one, technology gets cheaper, smaller and more powerful year over year," Johnson said. "And the other key was virtualization, which I describe as carpooling."

By virtualizing their servers, Dell was able to go from an industry average 12-18 percent utilization for its servers to 42 percent utilization, a number that Parker says is still "going north." As a result, "we've doubled our workload at no extra power, and no extra servers," Johnson said.