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Figure 5.11: Relative efficiency of fuel types for electricity generation, 2005

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(1) ‘Others’ includes wind, biogas, waste heat, wood, and cogeneration.

(2) PJ = petajoules.

Data source: Adapted from Ministry of Economic Development, 2006.

Text description of figure

Figure 5.11 illustrates the relative efficiency of fuel types for electricity generation. It presents a 'snapshot' of energy flows within New Zealand's electricity system using 2005 data. In 2005, the total primary energy supply for electricity generation was 293 petajoules, while the net amount of electricity generated was 149 petajoules. This represents an average efficiency of just over 50 per cent. The remaining 144 petajoules were lost as heat when transforming the primary energy sources into electricity and used as electricity within power stations. In 2005, 132 petajoules of electricity generated were used by consumers once further losses in transmission and distribution and statistical differences were taken into account.

On average, hydro and wind are almost 100 per cent efficient. By convention, geothermal generation is approximately 15 per cent efficient. The efficiency of thermal fuels such as coal and natural gas ranges from 30 to 50 per cent.