Computers have become, indirectly, a significant source of greenhouse gases, according to Kevin Klustner, CEO of Verdiem, a start-up that has devised software for curbing electricity consumption by PCs. That electricity often comes from coal-fired plants that release carbon dioxide.

Often, the power gets expended for no good reason.

"Thirty percent of the energy consumed by a personal computer is wasted because people aren't in front of it," Klustner said. He also cited a survey of IT managers who said employees tend to change the energy-saving settings on the PCs: The IT department might mandate a shutdown after three minutes of inactivity, but then people reset the default on their machines to extend that to, say, 10 minutes.

Sometimes, though, it's essential a machine keep running. Traders on a financial floor often study screens, but don't interact with their computers, said Klustner. In cases like that, an IT manager could set the PCs to stay on, even if no keystrokes have occurred for an extended period.

"A rule that says turn off your monitor after five minutes wouldn't work," he said. The rules on when to shut off PCs and for which employees are usually determined after a survey of the work habits of employees.

Conservation credibility
Seattle-based Verdiem hopes to capitalize on this problem by taking control of the energy settings out of the hands of the user. The company's Surveyor software remotely controls when and how desktops and laptops on a network go into an energy-saving sleep mode.

Other companies are tackling PC power consumption from different directions. New Hampshire's Degree Controls has created a network of sensors that can pinpoint hot spots in a server room and direct cool air there. Directional air flow can cut computer room power bills, often inflated by air-conditioning, by 30 percent, Degree Control says.

While start-ups have emerged in the past few years touting alternative-energy ideas such as ethanol or solar power, others have taken a dowdier tack and promoted energy conservation. Companies such as Comverge, for instance, have come up with ways to control thermostats remotely.

Although conservation isn't as sexy, it has strong adherents. Nobel laureate Steve Chu, for example, has said that fairly simple conservation techniques could substantially cut energy consumption without forcing a change in lifestyle in the U.S.

Regulations passed in the 1970s that forced appliance makers to reduce energy consumption have led to refrigerators today that consume about half the electricity of their 1973 counterparts. They also hold far more food.

The movement to cut power consumption by PCs--and servers--now includes a wide range of forces, including tech companies, advocacy groups and politicians. Some companies, such as Advanced Micro Devices, have made it a central tenet of their marketing.

Ecological, financial motivation
The savings from Surveyor can be fairly substantial, according to Verdiem. The company has found that the software can cut power bills by $20 per PC and reduce carbon dioxide emissions by 440 pounds a year. Fifteen PCs can generate as much carbon dioxide annually as a typical midsize car, according to the company, although the exact figure depends on where and how the electricity is generated and other factors.

So far, the software has been deployed on around 300,000 PCs. Most organizations that have installed Surveyor have 4,000 or more PCs on their networks. Some of the larger customers, such as School District No. 57, in Maryland's Prince George's County, have 30,000 seats.

Verdiem has had the most success with government agencies and school districts, Klustner said. Part of the reason, he said, is that these organizations are cost centers. They don't generate revenue. As a result, the only practical way to improve their financial picture they can directly control is by reducing costs.

The structure of the consultants that service these companies also helps. Technology giant Siemens and other organizations provide energy services to public institutions. These consultants don't get paid flat fees. Instead, they get a portion of what they can save their clients. As a result, many energy-services consultants have adopted the software. These companies have also begun to increasingly fish for clients in the private sector.

The software costs $20 per seat. Verdiem charges a $2 maintenance fee per year per seat after that. "You can get payback in about one year to 15 months," Klustner said.

The current version of Surveyor has two modes: It leaves PCs on or puts them into a sleep mode. It may be possible to come up with ways to save power by putting PCs into intermediate stages of energy consumption, according to the company.

Verdiem is also looking at ways by which the rules governing how a PC is put to sleep or remains active can be adjusted to an individual user.