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Q1: I’ve heard computers cost a lot of energy to create. I use my computer to save me traipsing around shops and paying bills. How many kilometres by 4-cylinder car would I have to drive to equal the energy of creating one computer?
Question submitted by Su Thomas

A: It depends on the life cycle analysis of the computer and the car. For instance, you could compare the energy used and greenhouse gases emitted in manufacturing and operating the computer with the costs of using your car. But you could probably argue that you bought both the car and the computer for many other reasons and only the operating energy use and emissions matter.

But comparing energy use and emissions would be difficult, as it depends on how long you use the computer for, and how far you would have to drive and in what type of traffic conditions.

For example, say you used the computer for one hour and avoided driving 25 km. If the computer and the monitor use 0.3 kW, then you would have used 0.3 kWh of electricity. On the Western Australian South West Interconnected System (Western Power), each kWh of electricity used produces about 1 kg of greenhouse gas emissions. So you would have produced about 0.3 kg of greenhouse gas emissions (carbon dioxide equivalents).

Around the city, a 4-cylinder car might use about one litre of petrol per 10 km. By using the computer for one hour, you avoided using 2.5 litres of petrol, which is equal to approximately over 2.5 kg of carbon dioxide emissions. So from a greenhouse perspective, in this example, you are around eight times better off using the computer.

– David Harries, Director, Research Institute for Sustainable Energy

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