According to a study by France’s environment agency your favourite jeans may are not doing the environment any good. Over the period of a year washing and tumble drying a pair of jeans uses up 240kWh of energy a year, equal to using 4,000 lightbulbs, each of 60 watts, for an hour. So why not wash your jeans a little less often, they may smell a bit but you can comfort yourself with the fact that your are doing your bit for the planet.