As Microsoft's Chief Environmental Strategist wrote in an article on Sustainable Facilities:
What we learned confirmed our hypothesis: Microsoft (and by extension, many organizations with similar real estate portfolios) don't need to undertake capital-intensive retrofits to cut building energy costs.
Instead, we saw buildings become dramatically more efficient by introducing software to harness and utilize the building systems already in use. By integrating powerful analytics that add intelligence to existing building infrastructure, our buildings got smarter, more efficient and less costly to operate. Follow think link for more details.