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Q2: We all know that compact fluorescent globes are more energy-efficient than tungsten incandescent globes, but how much energy is required to manufacture them? Is it true it takes more energy to turn the lights on than to leave them on — for example, if you are going out of the room for just ten minutes, should you turn them off or not?
Edited from questions submitted by Alan Bell, E Shanahan, John Gould and Shirley Gregory

A: Most compact fluorescent lamps are more energy-efficient than incandescent lamps. Compact fluorescents may be more energy-intensive to produce (they are technically more complex systems), but this additional embodied energy is very small and offset many times over by the energy saved over their operational life.

A recent life cycle comparison carried out by David Parsons says: "The claimed environmental benefits of CFLs over incandescent lamps is largely true and further that it is true on almost any measure, in spite of the greater use of materials in and greater complexity of the CFLs". [1]

It is true that fluorescent lamps draw an inrush current that can be five times greater than the operating current. However, the initial surge lasts for only a fraction of a second. This means you have to turn the lamp off for less than a second to save the same amount of energy used to start it up again. Start up times do vary depending on the type of lamp and ballast, but if you are leaving the room for more than a few seconds it is always better to turn the light off.

– Ross Carter, First Assistant Secretary of the Industry, Communities and Energy Division, Australian Greenhouse Office

[1] D Parsons, 2006, ‘The Environmental impact of compact fluorescent lamps and incandescent lamps for Australian conditions’, The Environmental Engineer, Journal of the Society for Sustainability and Environmental Engineering, Institution of Engineers; Vol 7, No 2, p 8–14

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