Although the environment is on many companies' minds these days, the economy arguably plays an even bigger role. That's why, although financial incentives went unmentioned during the announcement of AT&T's new power management strategy, it was certainly a main driver of the decision.

The telecom announced today that it would be installing the NightWatchman PC power management software from British company 1e on around 310,000 desktop computers in AT&T's U.S. facilities. As a result, AT&T expects to trim its electricity use by 135 million kilowatt hours every year.

That adds up to a lot of cash: if AT&T is paying around the U.S. average rate per kilowatt hour of electricity, it will save $13.6 million per year in electricity costs.

The move will also trim a huge amount of greenhouse gas emissions as well: AT&T estimates more than 120,000 tons of CO2 or CO2 equivalent avoided every year by saving all that electricity.

1e's NightWatchman software is one of several programs that IT managers can use to make sure that PCs are powered down during off hours, while still remaining accessible for software and security updates. In a study the company released last year, 1e estimated that about half of all corporate PCs in the U.S. are not turned off at night, costing around $1.7 billion in wasted energy every year.

Software to invisibly save energy like NightWatchman is increasingly on IT departments' radars as a relatively easy way to save significant costs. This summer, Verdiem and Microsoft announced a partnership to bring a free version of Verdiem's Surveyor softare to spread energy management further and wider.