According to a provisional assessment by the British Department of Energy and Climate Change, primary energy consumption decreased by 1.3 % in 2013, continuing the downward trend of the last 8 years, as 2013 was marginally cooler, with a small increase in the number of heating degrees day. The switch in electricity generation from coal to wind has resulted in a decrease in demand for primary energy, as wind consumption is measured as its energy output, whilst losses are recorded in transforming coal into electricity. With GDP growth of 1.9% in 2013, the energy consumption per unit of economic output is likely to have fallen by around 4% in 2013. Primary energy production fell by 6.7% on a year earlier to 113.9 Mtoe. This decrease was due to falls in fossil fuel extraction, with coal output down 24% as a result of the closure of a number of mines in 2013; oil and gas were down 8.8 and 7.3% respectively in line with the long term trend. This follows the sharp falls in UK Continental Shelf output of 13.4 and 10.7% in 2011 and 2012 respectively. Low carbon energy production grew, with wind generation from major power producers up by 38% largely reflecting additional capacity. Coal accounted for 40.7% of electricity supplied in 2013, with gas accounting for 26.7% and nuclear 21.1%. Despite a decrease in coal use in 2013, the contribution of coal to the UK’s electricity mix remains high compared to recent years (between 2009-2011 coal provided around 30% of the UK’s electricity generation). In 2013, the UK was a net importer of petroleum products for the first time since 1984, (the miner’s strike resulted in high demand for fuel oils). This change reflects lower domestic production levels following the closure of the Coryton refinery in July 2012.