1. A widely reported 2012 Greenpeace study estimated the global Internet (loosely, the “Cloud”) used 600 billion kWh in 2007. Greenpeace estimated that figure would triple by 2020, a growth rate that implies 1,100 billion kWh for 2013. A European Commission report published this year estimated 930 billion kWh for global ICT. Another recent report -- published last year and sponsored by 12 tech companies including Ericsson, Microsoft, Nokia, HP, Verizon, etc. -- yielded a number similar to the European Commission report. We note that in the interstices of all of the aforementioned reports, the data sources date back to 2010 and earlier, and in particular use network energy data circa 2007, before the rise of the smartphone and advent of the tablet. Our August 2013 report on global ICT electricity use -- where the Executive Summary sparked the controversy over the iPhone-refrigerator comparison -- found a higher figure of about 1,500 billion kWh. Our report used more recent data and, unlike other published work thus far, accounted for the very recent increase in wireless broadband as well as included other Internet connected devices, notably digital TVs.
2. We ignore in these calculations wired networks because mobile networks use 100 times more energy per unit of data.
3. At the low end of the range, for example, is a 2013 technical paper from University of Melbourne and Bell Labs estimating 0.1 to 0.2 kWh/GB for cellular broadband energy use. This range is based on the assumptions of a mixed use of local WiFi (to keep traffic off of the cell system) and utilization of the most efficient (not average) network equipment. At the other end of the spectrum, GSMA, the mobile operators trade association, has published a value of 19 kWh/GB in a 2013 paper, reported as a significant improvement over the 33 kWh/GB in 2009. An earlier 2005 technical analysis from Motorola, Swisscom, and Deutsche Telekom, provided 38 kWh/GB in 2004; this latter translates into 2.5 kWh/GB by 2013 based on the reported rate of improvement in network efficiency of 26%/yr. A technical paper from 2012 by Ericsson, Telecom Italia, Alcatel-Lucent, provides a range of 1 to 2 kWh/GB. Note: relevant to the exploration of energy use from wireless broadband, according to Verizon the latest high-speed 4G LTE cellular networks require two to three times more data traffic per hour to perform the same tasks as on the previous slower network.