But Wheeler is also feeling the heat. Customers are moving to 10- and 12-foot-high racks, in some cases increasing the power density by a factor of three. Right now, Terremark bills based on square footage, but he says collocation companies need a new model to keep up. "Pricing is going to be based more on power consumption than square footage," Wheeler says.

According to EYP's Gross, the average power consumption per server rack has doubled in the past three years. But there's no need to panic -- yet, says Donabedian.

"Everyone gets hung up on the dramatic increases in the power requirements for a particular server," he says. But they forget that the overall impact on the data center is much more gradual, because most data centers only replace one-third of their equipment over a two- or three-year period.

Nonetheless, the long-term trend is toward even higher power densities, says Gross. He points out that 10 years ago, mainframes ran so hot that the systems moved to water cooling before a change from bipolar to more efficient CMOS technology bailed them out.

"Now we're going through another ascending growth curve in terms of power," he says. But this time, Gross adds, "there is nothing on the horizon that will drop that power."