The two islands are geographically different – the South Island is 33 percent larger than the North Island in land area (151,000 km2 vs 114,000 km2), but the North Island has over three times the population of the South Island ( million vs million). As a consequence, the North Island has a substantially larger energy demand. However, the South Island uses more electricity per capita due to its cooler climate and the presence of the Tiwai Point Aluminium Smelter, which at a peak demand of 640 MW is New Zealand's largest single electricity user. In 2011, around 37.1% of the total electricity generated was consumed in the South Island, while 62.9% was consumed in the North Island. South Island generation accounted for 40.9% of the nation's electricity in 2011, nearly all (97%) from hydroelectricity, while the North Island generated the remaining 59.1% from a mixture of mainly hydroelectric, natural gas, and geothermal generation, plus smaller amount of coal and wind generation.