Interest in and production of renewable energy in Australia has undergone substantial growth since 2006. It is estimated that renewable energy produced 29,678 gigawatt-hours (GWh) of electricity (or equivalent) over the year ending December 2012, which represents 13.14% of the total production in Australia. This compares to 2011 with 29,302 gigawatt hours (GWh) of electricity (or equivalent) over the year ending September 2011, which represented 9.6% of the total production in Australia, and 2006 figures, when approximately 9,500 GWh of electricity came from renewable sources, representing less than 4% of electricity consumption for that year. Increases in solar and wind generation more than offset a decline in the contribution of hydroelectricity between 2011 and 2012. Of all renewable electrical energy sources in 2012, hydroelectricity represents 57.8%, wind 26%, bioenergy 8.1%, solar PV 8%, large-scale solar 0.147%, geothermal 0.002% and marine 0.001%; additionally, solar hot water heating is estimated to replace a further 2,422 GWh of electrical generation. This compares to 2011 figures where hydroelectricity represented 67.2%, wind 21.9%, bioenergy 8.5%. solar PV 2.3%, solar thermal 0.015%, wave and tidal 0.003% and geothermal 0.002%. Additionally, solar water heating units have been calculated to have offset the equivalent of 2115 GWh of electricity per year, which represents around 7.2% of total renewable energy production.