Pacific Gas & Electric, a California-based energy utility, is extending an energy-savings rebate program, already available for servers, to disk storage equipment.

PG&E provides rebates to companies that replace all or most of their data centers with new, more energy-efficient servers based on the scope of the replacement project and the projected energy savings. Such server vendors as Hewlett-Packard and Sun have had their products certified as eligible for use in the program.

PG&E earlier this year said it was collaborating with other U.S. electric utilities to share best practices on data center rebate programs. The idea is to make them as uniform as possible so a company with data centers in Texas and California, for example, can expect the same kind of rebate, said Mark Bramfitt, principal program manager for energy efficiency at PG&E.

Extending the rebate program to storage is a natural extension of the drive to improve energy efficiency in data centers, Bramfitt said.

Storage arrays could use an energy efficiency makeover. A storage array that includes 100 disk drives keeps all 100 of the disks spinning around the clock so that data can be quickly retrieved when needed, Bramfitt said. A software program called MAID, for massive array of idle disks, can identify which of those disks are little used and which data on those disks is little used. It backs up that data onto a portion of the disk drives and turns them off.

"So out of 100 disk drives, maybe 75 are now idle, so there's clear energy savings there," he said. If one of those idle disks is needed, it may take a little longer to retrieve data on it until it powers up, but if it's little used anyway, the delays won't add up to much.

The incentive program for storage, which will be formally announced later this month, will be similar to the server program, he said. A company will apply to PG&E for the rebates and provide details of the project it is undertaking. PG&E will then calculate the anticipated rebate based on the projected energy savings. Once the project is done, PG&E will inspect the new data center and verify the change was done according to the plan.

"Then we send them a check," Bramfitt said. PG&E calls it an incentive program because it tells the customer up front what their rebate could be as an incentive for them to complete the project.

Sun was the first vendor to have its hardware certified as eligible for PG&E rebates, though HP earned certification soon after. Sun says it is close to identifying a Canadian utility company that will offer a rebate on Sun servers and may announce deals with several other U.S. utilities as well.

But PG&E doesn't offer a rebate simply for buying an energy-efficient server, Bramfitt said. The customer has to do a "rip and replace" project, removing a sizable number of older servers or storage and installing new energy-efficient ones. The incentive program is also not available for brand-new data centers. The point is to replace old servers with new ones to reduce overall energy consumption.