This guide is based on UK law. It was written and last reviewed in January 2010.
The European Commission's Code of Conduct on Data Centres' Energy Efficiency (19-page / 65KB PDF) is a voluntary code that organisations can sign up to, committing them to implement some light-touch measures to reduce energy consumption. The latest version took effect from 1st January 2010. There is also a paper on 2010 Best Practices for the EU Code of Conduct on Data Centres (40-page / 439KB PDF)
The Code's stated aim is "to inform and stimulate data centre operators and owners to reduce energy consumption in a cost-effective manner without hampering the mission critical function of data centres."
The Code aims to achieve this "by improving understanding of energy demand within the data centre, raising awareness, and recommending energy efficient best practice and targets."
A list of participants shows that data centres controlled by Microsoft, Vodafone, Fujitsu, Intel and Hewlett-Packard are operated in accordance with the Code. Participation is voluntary.
See: Further information on the EU Code of Conduct for Data Centres