The sheer number of ways to measure and quantify "greenness" is probably the most difficult aspect of this effort, a combination of the vast number of opinions as to what is and is not energy efficient and the penchant for technologies to reduce the environmental impact in one area only to increase it in others.
But even as some people throw up their hands over the deficiencies of Power Usage Effectiveness (PUE), which even its creators say is not meant to be a full gauge of energy efficiency, the drive continues to at least make progress in reducing the draw from one of the most energy-intensive industries on the planet.
In Europe, the focus has shifted from new building and construction practices to the ways in which normal operations can be improved. The British Computer Society has devised the Certified Energy Efficiency Datacenter Award (CEEDA) program, which seeks to cover a wide range and operations such as equipment utilization, power and cooling, building design and overall monitoring. The idea is to wean the industry away from self-certifying programs like the EU Code of Conduct and more toward independent verification of best practices.
That kind of overall picture of environmental health is becoming easier to quantify with the arrival of a new generation of metrics designed not only to measure power consumption but to relate that consumption to data processing capabilities. In this way, according to Power Assure CTO Clemens Pfeiffer, new tools like the Corporate Average Datacenter Efficiency (CADE) and Power to Performance Effectiveness (PPE) programs offer insight into overall efficiency, rather than raw energy usage.
Another entrant is the Data Center energy Productivity (DCeP) metric, under development by the EPA for use in its Energy Star evaluations. The agency has been under a fair amount of criticism for its adoption of PUE for making Energy Star certifications, which by itself would not have bothered the enterprise industry too much except for the significant tax advantages that an ES designation bestows.
Understand, however, that PUE still has value, if only as a means to determine how much of your energy draw is going toward actual data services, rather than to support functions like heating, cooling and lighting. The Green Grid, developers of PUE, is also supplementing it with similar metrics to assess water usage and carbon output.
Despite the plethora of new tools and government incentives, there probably won't be a definitive means to measure efficiency save one: If your data center provides the same level of service while your energy bill goes down, you're probably on the right track.