Sir

Your News Feature 'Electricity without carbon' (Nature 454, 816–823; 2008) claims that the easiest way to cut the carbon released by electricity generation is to “increase efficiency”. Although efficiency measures do have the potential to cut emissions, this applies only under the optimistic assumption that efficient energy converters will not be used more than their inefficient predecessors. This assumption has been challenged by Vaclav Smil in his Correspondence 'Long-range energy forecasts are no more than fairy tales' (Nature 453, 154; 2008), who argues “We have known for nearly 150 years that, in the long run, efficiency gains translate into higher energy use”.

Given the thermodynamic and economic limitations of efficiency measures, the easiest way of reducing emissions is also the simplest: cut usage of existing energy converters. For example, incentive-based regulation, real-time electricity metering and rethinking behaviour could all considerably reduce demand for electricity and therefore its associated emissions. In combination with efficiency gains and renewable energy sources, such an approach would create better conditions for a smooth transition to a carbon-neutral economy.

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