The energy efficiency retrofit industry for public buildings is relatively well developed worldwide compared to the private building retrofit industry. It is a large market in the United States, with annual revenues for energy service companies in the vicinity of U.S. $4 billion. However, long-term energy efficiency and carbon mitigation targets worldwide will rely heavily on improving the efficiency of the entire building stock. Public buildings represent only about a quarter of the total commercial building stock in the United States, and retrofits have barely begun to touch the private building stock.

One reason for the sluggishness of efficiency in the private building stock is the lack of post-retrofit data on building performance. Although there are many successful examples of retrofits in the private sector, the industry as a whole needs a robust set of data on post-retrofit performance and payback before they will be convinced that the opportunity to reduce operating costs is real, the risks are low, and the ROI is high enough to justify investments in efficiency.