The electricity consumed by a server over its lifetime is likely to cost as much as the server itself if energy costs continue to rise, according to one analyst. That should make energy efficiency a key concern for data centre managers -- and it's a concern that server vendors are increasingly addressing.

"If you take a server where the processor is using 80 to 90 watts, and factor in all the other hardware to support that -- air conditioning, storage and so on -- the cost of the electricity used by that server is on a par with the cost of the server over its life," said Steve Prentice, an analyst at Gartner, speaking at the International Cebit Forum.

"I don't see IT managers replacing servers just for environmental reasons, but if it's to slash 40 percent to 50 per cent off electricity costs, that's serious money," Prentice said.

As technology evolves, indirect energy costs for things like cooling are increasing, Prentice said. "In the data centre, as the density of hardware increases, then heat is a bigger problem," he said.

Vendors said that the concerns that customers discussed with them at the CeBIT trade show bear that out.

"They are asking more in the area of small blade servers, because they want to calculate the total power consumption in their blade server farm," said Bernd-Dieter Heise of Fujitsu-Siemens Computers GmbH.

Making that calculation can require a detailed knowledge of a server's specifications.

Fujitsu-Siemens has long prided itself on the energy consumption of its servers. A PrimeQuest 400 with 32 Itanium processors and 1TB of memory consumes 10.7 kilowatts of electricity and, fully equipped, has a list price of around $1.08 million, according to Heise.

A comparable system from a rival vendor consumes 16 kilowatts, he said.

Sun Microsystems too, touts the reduced power consumption of its newest servers equipped with Sun's UltraSparc chips. The power and space savings that can be realised by using such servers can be a tough sell, though.

"The marketing teams just want speed; they don't think of power, space and cooling," said Steve Campbell, Sun's vice president of data centre insight.

That could change as more customers realise how much they spend powering their data centres. The University of Tokyo recently found power to be its largest budget item, at more than $1 million a year, Campbell said.

Not everyone is worried about their IT electricity bill, though, according to Fujitsu-Siemens' Josef Zitzlsperger. "For mainframe customers, it's not a priority," he said.

Even where money is no concern, power shortages can still force organisations to reduce consumption -- and not just in underdeveloped regions.

In the summer, Sun sometimes has to power down its servers in San Diego if available power in the city is limited, according to Campbell. "That's in the US, one of the richest economies of the world," he said.

Such events are still rare in Europe, but a heat wave in France in 2003 highlighted the fragility of electricity supplies there. Electricity consumption by air conditioning systems soared, and some power stations faced the threat of having to shut down because their own cooling systems had trouble coping.

Perhaps that's what prompted server manufacturer Bull SA to highlight energy efficiency when it launched its Novascale 2320 Blade at CeBIT.

The blade has a dual-core, low-voltage Intel Xeon processor and carries up to 8GB of memory and two internal 2.5-in. serial-attached SCSI disks, and it offers "the best available performance per watt in the industry," according to the company.

However, Bull representatives were unable to give a figure for the device's actual power consumption at press time.