Despite a 13% increase in energy usage at our data centres in 2011 through increasing online delivery of our products and services, total energy stayed reasonably constant with a 2% decrease in absolute terms. This was due in part to a 12% reduction in total energy usage at our office locations, following space consolidation and reduction efforts by the global real estate team.
We realise the challenge in reducing absolute energy usage while continuing to grow our business, and therefore have set targets to increase renewables. In 2011, we purchased 23% of our electricity from renewable sources compared to 13% in 2010. We have set an objective to increase this to 30% in 2012, 50% in 2015, and 100% in 2020. As we are predominately in leased locations with few opportunities for onsite generation, we will rely on green tariffs and renewable energy certificates, with offsets as necessary.
12012 and 2013 results forecasted based on expected energy growth.
In 2011, 63% of our revenue was from online products and services. This was mirrored in energy use at our data centres, now responsible for 47% of total energy usage (offices account for 48% and warehouses 5%). We expect data centres to be responsible for 50% of our total energy usage by 2013 and, as such, will continue to focus our reduction efforts here. In 2011, we carried out a data centre efficiency study at our Springfield, Ohio data centre with the help of IBM, which identified lighting, air management, and operational improvements, which we have begun to implement and roll out to other data centres. We will continue to purchase more efficient hardware and work with industry advisers on opportunities for consolidation and virtualisation.
In 2011, average Power Usage Efficiency across all of our major data centres improved from 1.75 in 2010 to 1.724, and our target is to achieve 1.7 by 2015, even with increased demand. We are members of the Uptime Institute and founding members of the Digital Sustainability Group, releasing new guidance in 2012 on the full life cycle of online information across the media sector.
In our offices, we added more sub-metering to better monitor and manage energy usage and ran training courses for facility employees to help them understand the data. Work by our contractors Grubb & Ellis in the US helped us expand our EPA Energy Star certification to two more large US locations. As well as continuing to upgrade lighting, replacing halogen lamps with more efficient LED fixtures, and fitting more daylight and motion sensors, we installed outdoor air economizers, utilising free air from outside the building for cooling; re-roofed and insulated buildings to trap heat in the winter and added reflective top sheets to reflect heat in summer; and continued to implement simple measures like shutting doors to conserve heat, using blinds and reflective film to stop solar glare, and running local switch off campaigns.