Energy is measured in ‘petajoules’ – one petajoule is equal to 28 million litres of petrol, or 277.7 gigawatt-hours of electricity. In 1924 New Zealanders used 86 petajoules of energy – by 2000 it had risen to 772. In 2008 primary energy came from:
- oil – 37.7%
- gas – 22.6%
- geothermal power – 12.5%
- water (hydroelectricity) – 11.3%
- coal – 9.2%.
Water and geothermal power are renewable energies – they don’t use up resources in the environment. Other renewable energies such as wood, wind and solar power, and biogases provided 6.7% of energy.
There are a number of large oilfields off New Zealand’s coasts. The oil mined off Taranaki is of high quality and is exported overseas, and the transport system relies on cheaper imported oil. In 2005 oil was used by:
- transport – 84% of oil
- industry – 6.7%
- agriculture – 4.9%
- commercial sector – 3.5%
- residences – 0.9%.
Crude oil arrives by tanker and is refined at Marsden Point refinery near Whangārei. Large pipelines carry petrol and aviation fuel from Marsden Point to Auckland, and petrol is transported around the country by tankers.
In 1924 New Zealanders used one petajoule of electricity – by 2007 they used 140.5 petajoules. At first the power was only on for a short time each day. In 2007 power was carried to homes and businesses by 39,000 kilometres of underground cables and 56,000 kilometres of overhead cables. There were 80 kilometres of underwater cables, including the one carrying power generated by South Island rivers and lakes across Cook Strait to the North Island.
Coal and gas
Coal used to be a major energy source for New Zealand – in the 1940s it supplied 45% of energy. By the 1970s it was 20%. In the 2000s the Huntly power station was using 2.5 million tonnes of coal a year. Electricity generation and steel milling used the bulk of coal.
Gas made from coal was common from the 1860s and coal gas was used for cooking, lighting and heating. In 1974 it was replaced by natural gas.
Taranaki has large gas fields. Natural gas is clean and odourless. A smell is added to it so people notice gas leaks – it is highly flammable. Gas is sent around the North Island by large high-pressure pipes. In 2007 gas was used for:
- electricity generation – 59%
- methanol and ammonia/urea production – 15%
- commercial use – 3%
- residential use – 3%
- other uses – 20%.