Electric cars and more efficient ways of cutting carbon emissions

The Guardian, Monday 20 April 2009

Dr Rob McMinn and Peter Evennett question the effect on energy efficiency of moving to electric cars (Letters, 17 April). One way of quantifying this is by calculating the distance covered per unit energy content for each of the respective fuels (electricity and petrol). To get a comparison over the full "well-to-wheel" cycle, overall efficiencies can be established by taking into account the efficiencies of extraction, generation, transmission, distribution and motor/engine performance for each fuel type. One set of published figures indicates that a high-performance electric car reaches more than twice the well-to-wheel efficiency of the most efficient of current petrol-driven models. In kilometres per megajoule of energy (km/MJ), the figures are 1.14 (electric), compared to 0.52 (petrol). These equate to CO2 emissions of roughly 13 grams per kilometre and 39g/km respectively. The analysis assumes electricity generation from high-efficiency combined-cycle natural gas plants, so for existing coal-fired plants the difference would be less. But we should anticipate that the transfer to electric cars on any substantial scale would be likely to take a decade or more, by which time electricity generation should depend on a far greater proportion of cleaner sources. Philip CoghlanRomford, Essex
A simpler, cheaper, more effective strategy for reducing carbon emissions (Labour's £5,000 sweetener to launch electric car revolution, 16 April) would be to encourage home-based work. Travel to and from work accounts for 30% of UK surface emissions and people, in general, don't enjoy commuting. Home-based work is a popular, family-friendly, environmentally sustainable working practice. For goodness sake, don't encourage everyone to buy a new car.Dr Frances HollissResearch fellow, Cities Institute, London Metropolitan University
With scientists issuing ever more frantic warnings about climate change, the government's proposed £250m fund to provide grants of up to £5,000 to encourage the purchase of electric cars has to be worth considering. However, I cannot help thinking that the government could spend the money on creating cycle-friendly streets. Cycling is far greener than any electric car will ever be. What is more, it helps reduce congestion, tackle obesity and improve road safety as well.Roger GeffenCTC, the national cyclists' organisation