Companies are finding large energy savings by adopting smart-building technologies that also provide other benefits, executives said on Tuesday at Fortune’s Brainstorm E conference in Austin, Texas.

Joe Costello, CEO of a Silicon Valley energy technology company called Enlighted, said his company’s clients are cutting their lighting bills by 60% to 70% and cutting heat and air conditioning bills by 20% to 30%. “The energy savings pays for the installation of the network,” he said, referencing the smart-building technologies, “and gives you data that enables a ton of other applications,” including asset tracking.

Costello made the comments during a breakfast session called “The Zero-Energy Corporation.” The business leaders who participated shared a variety of tactics they had used to cut energy usage and adopt clean energy sources.

Thierry Van Landegem, chairman of GreenTouch, an information technology consortium focused on sustainability, told of reducing energy usage in the mobile phone business “by a factor of 10,000.” Mobile technology was developed without energy usage as a consideration, he explained. Companies can save large amounts of energy by getting cellular towers to go into “sleep” mode when usage is low, for example.

Bill Weihl, director of sustainability at Facebook FB , said his company has been able to cut energy usage at its data centers by 38%. Facebook has pledged to obtain all of its energy from renewable resources.

Virtually all of the participants at the breakfast agreed that companies are leaving large cost savings on the table by not moving toward a variety of energy savings technology.

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