The total geothermal capacity overcomes 600 MW, with a contribution of 10% of the total country electricity generation. Several additional projects are ongoing, with very ambitious target for year 2015, reaching 15% of geothermal electricity. Presently, there are 122 MW at Kawerau, 111 MW at Mokai, 25 MW at Northland (Ngawha), 103 MW at Reporoa (Ohaaki), and 232 MW at Wairakei.

Wairakei celebrated the fifty years of operation, since the commissioning of its first turbo-generator in 1958. It is operated by Contact Energy. Many modifications have been made over the years, the latest being the installation of a 14 MW net binary cycle in 2005. Development project for a new unit is ongoing. It is planned a future replacement of several old units with a new power block, called Te Mihi, with a net increase of 65 MW due to the increase of efficiency.

In Reporoa, the Ohaaki plant was originally developed to 114 MW, and after the decommissioning of one unit it has been reassessed to 103 MW; however, its production was dramatically low, down to 25 MW; since 2006 the operator (Contact energy) invested in new wells, reaching 65 MW of production, maintaining it through alternative production and injection strategies to minimize concerns over subsidence affecting Waikato River.

Mokai had progressive development since 1999 up to 112 MW using binary cycle technology, operated by the largest independent private generator of electricity nationally, Tuaropaki Power Company. A further 39 MW in 2005 and re-engineering of the first stage with another 17 MW in 2007 have been realized.

Kawerau field started electricity production with a small generator in 1966, replaced by in 2005. The single largest step in New Zealand’s geothermal generation have been done by Mighty River Power, with the development of a 100 MW double flash power station, commissioned by the end of August 2008. The field is operated by Ngati Tuwharetoa Geothermal Assets. Moreover, an 8 MW binary unit (KA24) has been added to the overall field capacity. Rotokawa field is large, hot and permeable and has significant potential for large scale development (Ngati Tuwharetoa Geothermal Assets and Mighty River Power). The first development for electricity generation took place in 1997 with the commissioning of a 29 MW binary cycle plant, later expanded to 35 MW. Construction work is well advanced for a new Nga Awa Purua triple flash, single Fuji unit development of 132 MW, expected to be commissioned in May 2010: it will be the largest development in New Zealand after the initial exploitation of Wairakei 50 years ago, and the largest single geothermal turbine in the world.

Top Energy in association with local Maori Trusts, started in 1998 with a 10 MW Ormat binary plant installed in Ngawa, Northland field. In October 2008 a 15 MW binary extension was commissioned; the field capacity is estimated larger than the currently installed, but it is not clear when further development will be realized.

The growing of the geothermal electricity in New Zealand, starting since 1950, after an initial increase had a long stabilization in production; an impressive new construction phase started in ’90 and after 2005, with very good short term perspectives, and the ambitious target of doubling the present capacity in year 2015. The 2005-2010 period had about 200 MW of new plant installed, with the very good increase of 44%.