by Bernard Aebischer

Technological innovations have wrought many transformations on society. The steam engine opened the way to the industrial society and the aeroplane revolutionized travel. Now, from the telephone to the internet, ICT is putting us on the path to a fully interconnected and radically different world.

However, with the advent of climate change, the next transformation to society may be driven by environmental considerations and the need to reduce energy consumption. Determining the contribution of ICT to global energy use is complex and difficult. The present article considers several ways of approaching an answer.

What does ICT comprise?
ICT is usually thought of simply as end-use devices such as computers, other office equipment, entertainment electronics and telephones, with the infrastructure required by this equipment being neglected. But this hidden infrastructure (eg the servers that provide Internet services and the radio antennas necessary to make mobile phone calls) now represents a significant and increasing fraction of ICT electricity consumption.

Even all this end-use equipment and related infrastructure represents only a small fraction of the microprocessors produced and used in industrial processes, buildings, appliances or cars. Rejeski (Anticipations. In “Sustainability at the speed of light”, 2002) said that “…only 2 percent of the approximately 8 billion microprocessor units produced last year ended up in computers.” And “…there could be as many as 10,000 telemetric devices per person in the industrialised countries by 2010.” And “Within a decade more things will be using the internet than people. As Michel Mayer, the head of IBM Pervasive Computing recently noted”. Turley (Motoring with microprocessors, 2003) wrote that “…the average middle-class American household includes over 40 embedded processors. About half are in the garage…. Your transportation appliance probably has more chips than your internet appliance… New cars now frequently carry 200 pounds of electronics and more than a mile of wiring”.

These observations are important for the estimation of the energy demands of ICT and essential for evaluating the impact of ICT on society’s energy requirements. And whenever investment figures for ICT are quoted, the categories of ICT included in these investments should be clearly stated.

Direct electricity demand of ICT
Taking into account the end-use equipment described above and its related infrastructure (servers, routers, switches for the Internet, base station switching units and others for telecommunication), typical calculations for an industrialized country suggest ICT accounts for about 5% of total electricity demand.

Knowing that the majority of microprocessors are in applications other than this equipment, we assume a doubling of the electricity demand for ICT. The resulting 10% is of the order of 1 mega watt hour (MWh) per capita and year. 1 MWh/year is a considerable amount of electricity in an industrialized country and it is more than what is used in many countries in the southern hemisphere. This is of course a very rough estimate, but we believe its accuracy to be sufficiently good for us to use it as a basis for the qualitative considerations in this paper.

Impact of ICT on energy demand
As well as measuring the direct energy demands of ICT equipment, it is also necessary – though much more complex – to determine the indirect impact ICT has on the overall energy demand of a country. To do so, one must consider:

  • energy demand over the life cycle of different types of equipment, ie in addition to the direct energy demand discussed above, the energy for producing, distributing and refurbishing or recycling this equipment
  • efficiency improvements as a result of the ICT in technical and economic processes; of vehicles and mobility in general; and of buildings, appliances and other energy-consuming activities
  • structural changes of and within the economy, substitution between services, dematerialization of the economy, and
  • acceleration of economic growth thanks to better productivity and rebound effects.

There are two approaches to studying the effect of ICT on energy demands. One is a microeconomic approach consisting of a bundle of case studies, where the impact of ICT on specific services and on the energy intensity of each service is analysed. The other is a macroeconomic approach, where the impact of ICT on the economic growth and on the energy intensity of the economy is investigated.

Most of the case studies to date investigate one of the following fields:

  • manufacturing or technical processes
  • building automation and intelligent homes
  • traffic management
  • e-economy with e-commerce, e-work, e-learning and e-governance.

The domain of manufacturing and technical processes is the only one in which most studies agree that ICT substantially reduces energy input.

Automation in buildings clearly has great potential to reduce energy use, particularly in large and complex buildings in the service sector. Information systems are implemented and used in modern buildings, but we know of many examples where the many thousands of data gathered and stored by these systems are not exploited to optimize energy use. In single family houses, ‘intelligent systems’ tend to lead to an increase in energy services and to a corresponding increase in energy demand (Aebischer and Huser, 2000, 2003).

Much time and energy is wasted in traffic jams. ICT can make traffic more fluid but at the same time it increases traffic flow – as when building a new road in order to decongest an existing one.

Most of the case studies investigate the impact of increased use of ICT in specific sectors of the economy. New organizational forms (e-work, e-commerce) and new products (e-paper, e-governance) are compared to traditional services and processes. Most of the studies do not question whether there is really a substitution between the traditional and the new service, and/or whether time and money saved by these new processes and services may lead to new energy consumption that balances or even negates the original savings.

An alternative approach: Spreng’s triangle
An alternative conceptual framework with which to examine the question of the impact of ICT is Spreng’s triangle (Spreng, 1993). Spreng describes all economic activity in terms of time, energy and information. The precondition is that there is perfect substitutability between the three factors. Then information can be used to replace time, accelerating innovation cycles and increasing productivity without increasing energy demand. Information can just as easily substitute for energy (or natural resources) without increasing the time, labour or capital input. In reality however, a saving of time (or increased productivity) through more information tends to increase energy demand, whereas more rational use of energy thanks to information may demand more time (see Figure).

Figure 1: The time-energy-information triangle (Spreng, 1993).

Spreng writes: “The importance of new information technology, NIT, in respect of future energy use can hardly be overstated. However, NIT can do two things. It can be used to substitute time by information or to substitute energy by information. NIT can, in other words, both be used to speed up the pace of life (work and leisure), thus promoting a society of harried mass consumers, or it can be used to conserve precious natural resources (energy and non-energy) by doing things more intelligently and improving the quality of life without adding stress to the environment. It is up to the society as a whole, politics of course included, to decide which of the two roads are taken.” (Spreng, 1993).

A more comprehensive and detailed essay “ICT and energy: methodological Issues and Spreng’s triangle” with illustrations and literature references can be found in "The European e-Business Report 2008“, p. 265: EBR08.pdf

Please contact:
Bernard Aebischer
CEPE, ETH Zurich, Switzerland
Tel: +41 44 632 41 95
E-mail: baebischer@

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