Mercury Energy

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IndustryElectric power generation
PredecessorECNZ, Mighty River Power
Founded1 April 1999 (1999-04-01)
Key people
Vince Hawksworth (CEO)
ProductsElectric power
ServicesElectricity retailing
RevenueIncrease NZ$2,000M (2019)[1]
Decrease NZ$505M (2019) [1]
Increase NZ$357M (2019) [1]
Total assetsIncrease NZ$6,484M (2019) [1]
Total equityIncrease NZ$3,537M (2019) [1]
OwnerNew Zealand Government (51.15%)
Number of employees
SubsidiariesGLOBUG (Prepay Power) Bosco (services Apartment buildings)

Mercury NZ Limited is a New Zealand electricity generation and electricity retailing company. All of the company's electricity generation is renewable. It owns and operates nine hydroelectric generating stations on the Waikato River and five geothermal plants in the Taupo area.[2]

In 2015, the company under the Mighty River Power brand generated 17% of the country's electricity.[3] In 2017, Mercury had a 19% share of the New Zealand retail electricity market.[4]


Mercury NZ Ltd[edit]

Logo of the former Mercury Energy

Mercury NZ Limited was formed in 1994 by the Auckland Energy Consumer Trust to own and run the electricity supply business previously operated by the community-owned local authority, Auckland Electric Power Board. In 1998, law changes obliged AEPB to sell the electricity retailing and generation part of the business.

Following the 1998 Auckland power crisis Mercury's electricity retailing division was sold to Mighty River Power, which was then a wholly state-owned SOE. Mighty River Power's retailing division continued the former trading name Mercury Energy. The electricity distribution business, Mercury Energy Limited, changed its name to Vector Limited and continued the distribution and transmission operation.

Mighty River Power[edit]

Logo of the former Mighty River Power

Mighty River Power was established on 1 April 1999, when the 1998 reform of the electricity sector took effect. The Electricity Corporation of New Zealand (ECNZ) was broken up into three state-owned generating companies - Mighty River Power, Genesis Energy and Meridian Energy. Mighty River Power took over the ownership and operation of the eight hydroelectric power stations on the Waikato River, New Zealand's longest, and also inherited the assets of two largely decommissioned oil-fired power stations at Marsden Point, near Whangarei.

In addition, the 1998 reforms forced the separation between lines (transmission and distribution) and supply (generation and retailing). On 1 April 1999, Mercury Energy, then the major lines and supply company for Auckland, New Zealand's largest city, was split between lines and supply. Mighty River Power inherited Mercury Energy's retail base and its share in the Southdown Power Station (in conjunction with the Natural Gas Corporation). Mercury Energy then became the name of Mighty River's retail business, and the sub-transmission and distribution business of Mercury Energy was renamed Vector.

In 2000, Mighty River purchased into the Rotokawa geothermal power station, to operate and maintain the station, and own the geothermal turbines in a joint venture with the Tauhara North No.2 Trust. Also that year, Mighty River Power commissioned the Mokai geothermal power station in a joint venture with the Tuaropaki Trust.

In September 2002, Mighty River gained 100 percent ownership of the Southdown power station.

In 2004, Mighty River announce plans to refurbish the Marsden B plant to fire it on coal to increase supply security north of Auckland. Marsden B had been mothballed since it was completed in 1978 due to rising oil prices following the 1973 oil crisis and there being cheaper alternatives available. Greenpeace staged a nine-day occupation of the site in 2005, and after the Northland Regional Council granted consent, appealed to both the Environment Court and High Court, eventually overturning the consent. Mighty River appealed the High Court decision to the Court of Appeal, but in March 2007 dropped the proposal.

In 2008, Mighty River increased its generating capacity by opening the 100 MW Kawerau geothermal power station, increasing supply security to the eastern Bay of Plenty, a large timber processing area. In 2010, it opened the 140 MW Nga Awa Purua geothermal station near Taupo, complete with the largest single-shaft geothermal turbine in the world. The commissioning of Nga Awa Purua increased Mighty River's geothermal capacity to 385 MW, becoming the nation's largest geothermal electricity generator with 52.7 percent of all installed geothermal capacity.

Partial privatisation[edit]

In December 2011, the National Government announced plans to reduce its shareholding in Mighty River Power, as well as in the three other state-owned energy companies, from 100 percent to 51 percent and to sell off the remaining 49 percent as part of its controversial "mixed-ownership model" plan. Mighty River Power was to be the first company to be partially sold in September 2012, pursuant to legislative changes and market conditions.[5][6] However, threatened legal action and unfavourable market conditions saw the government delay any sale until March 2013 at the earliest.[7]

The Government began taking registrations of interest from the public in Mighty River Power shares on 5 March 2013.[8][9] More than 35,000 people tried to register in the first six hours,[10] causing the registration website to crash for much of the day.[11][12] By midnight, more than 90,000 people had registered.[13][14]

In anticipation of the sale, in April 2013 State Owned Enterprises Minister Tony Ryall said director fees would be increasing from $49,000 a year to $85,000, and the chair's fees from $98,000 to $150,000, despite still being majority-owned by taxpayers.

The Financial Markets Authority approved the sale of Mighty River Power on 12 April, with the initial public offering (IPO) opening on 15 April.[15] However, the IPO was temporarily suspended on 22 April while a supplementary disclosure was issued, after the Labour and Green parties in opposition announced plans to reform the electricity market if elected to government at the 2014 election. At the close of the IPO on 5 May, there were 113,000 shareholders, and on 8 May the opening share price was set at $2.50, raising $1.7 billion.[16] The Government was slightly disappointed, blaming the Labour-Green policy for putting off many more potential shareholders, and with the Finance Minister indicating before the policy was announced that the price would be in the $2.70 to $2.80 range.[17] The government retained 51.78 percent of the shareholding, with another 1.02 percent owned by other Crown interests (mainly the New Zealand Superannuation Fund).[18]

By September, shares had slumped to $2.16, well below the float price,[19] and in October the company announced it would be buying back up to $50 million in shares.[20] By November 2015, the share price had exceeded the listing price, at $2.88.

The gas fired Southdown Power Station, a 170 MW combined cycle power station in south Auckland was closed in December 2015.

Name change[edit]

The company changed its name to Mercury NZ Limited on 29 July 2016, after merging its retail and generation businesses.[21] The company also launched a new brand logo, moving from the Roman god Mercury, to a bee. Market research showed New Zealand had a stronger connection to the bee as a symbol. [22]

Power stations[edit]

Mercury operates 13 power stations, all in Auckland, Waikato, and the Bay of Plenty. In total, the company has 1638 MW of generating capacity - composed of 1078 MW hydroelectric, 385 MW geothermal, and 175 MW natural gas.

Name Type Location Capacity
Annual Generation
(average GWh)[23]
Commissioned Notes
Arapuni Hydroelectric Waikato River 196.7 864 1946
Aratiatia Hydroelectric Waikato River 78 333 1964
Atiamuri Hydroelectric Waikato River 84 293 1962
Karapiro Hydroelectric Waikato River 96 506 1948
Kawerau Geothermal Kawerau, Bay of Plenty 100 831 2008
Maraetai Hydroelectric Waikato River 360 875 1954, 1971
Mokai Geothermal North-west of Taupo 112 926 2000 Joint venture with Tuaropaki Trust
Nga Awa Purua Geothermal North of Taupo 140 1132 2010 Joint venture with Tauhara North No.2 Trust
World's largest geothermal turbine (147 MW rated)
Ngatamariki Geothermal North of Taupo 82 687 2013
Ohakuri Hydroelectric Waikato River 112 402 1962
Rotokawa Geothermal North of Taupo 33 270 1997 Joint venture with Tauhara North No.2 Trust
Waipapa Hydroelectric Waikato River 51 239 1961
Whakamaru Hydroelectric Waikato River 100 494 1956

Acquisition of Wind Farms from Tilt Renewables[edit]

In 2021 Mercury partnered with Powering Australian Renewables (PowAR) to enter into a Scheme Implementation Agreement (SIA) with Tilt Renewables Limited. Under the terms of the transaction, PowAR will acquire all the shares of Tilt (including Mercury’s shares) for NZ$8.10 per share, and Mercury will acquire all of Tilt’s New Zealand operations, including its future development options.

In addition to Tilt shareholder approval, the Scheme is conditional on High Court approval, and regulatory approvals but the deal is expected to be finalized by August 2021 – the assets acquired will be:

Name Type Location Capacity (MW) Annual Generation (average GWh) Commissioned Notes
Tararua Wind Farm I & II Wind Tararua Ranges 68MW 245GWh Stage 1: 1991 Stage 2: 2004 Tararua is currently NZ's largest wind farm
Tararua Wind Warm III Wind Tararua Ranges 93MW 318GWh 2007 Tararua is currently NZ's largest wind farm
Mahinerangi Wind Farm Wind Otago 36MW 101GWh 2011
Waipipi Wind Farm Wind South Taranaki 133MW 455GWh 2021

Generation developments[edit]

Name Type Location Planned
Capacity (MW)
Puketoi Wind Puketoi Ranges Consent application lodged August 2011.[24] granted June 2012[25]
Te ia a Tutea Geothermal North-east of Rotorua Initial exploration[26]
Turitea Wind South-east of Palmerston North 220 Under construction.

International developments[edit]

Name Type Location Planned
Capacity (MW)
Hudson Ranch Geothermal California, USA 50 Opened May 2012[26]
Tolhuaca Geothermal Southern Chile Exploration[26]
Puchuldiza Geothermal Northern Chile [27]
Weilheim Geothermal Germany Exploration[26]


In addition to its generation assets, Mercury also incorporates or has major shareholdings in:

  • Bosco Connect, an electricity retailer to inner city apartments
  • Glo-Bug, a pre-pay electricity retailer
  • What Power Crisis, supplying Solar Power installations as Mercury Solar

See also[edit]


  1. ^ a b c d e "Annual Report 2019". Mercury Energy. 23 August 2019.
  2. ^ "Generation". Mercury Energy.
  3. ^ "Energy in New Zealand 2016". MBIE. September 2016. Archived from the original on 15 February 2016. Retrieved 11 June 2017.
  4. ^ "Market share trends". Electricity Authority (New Zealand). Missing or empty |url= (help)
  5. ^ Romanos, Amelia; Bennett, Adam (15 December 2011). "Mighty River Power first SOE to go". The New Zealand Herald. Retrieved 12 January 2012.
  6. ^ "Mighty River Power first state-owned asset to be sold - English". 3 News. 15 December 2011. Retrieved 12 January 2012.
  7. ^ Watkins, Tracy (3 September 2012). "Sale of Mighty River Power delayed". Fairfax Media (via Retrieved 15 October 2012.
  8. ^ Gower, Patrick (5 March 2013). "Mighty River sale opens". 3 News NZ.
  9. ^ "Market may take a hit as Mighty River sale attracts 'huge interest'". NZ Herald. 4 March 2013.
  10. ^ "Brokers contact Mighty River investors". 3 News NZ. 6 March 2013.
  11. ^ "Mighty share website crashes". 3 News NZ. 5 March 2013.
  12. ^ "Mighty River share website crashes". NZ Herald. 5 March 2013.
  13. ^ "Mighty River share registration high". 6 March 2013.
  14. ^ "Demand for Mighty River hits 90,000". 3 News NZ. 6 March 2013.
  15. ^ "Mighty River sale gets FMA approval". 3 News NZ. 12 April 2013.
  16. ^ Hutchison, Jonathan (10 May 2013). "Shares Rise After I.P.O. of New Zealand Power Utility". NY Times.
  17. ^ Bennett, Adam (9 May 2013). "Mighty River $2.50 price hit by power policy". The New Zealand Herald. Retrieved 9 May 2013.
  18. ^ Parker, Tasmyn (17 May 2013). "Stock Takes: Mighty nervous". The New Zealand Herald. Retrieved 17 May 2013.
  19. ^ MightyRiverPower pair snap up shares. 3 News NZ. 30 September 2013.
  20. ^ Mighty River Power to buy back shares. 3 News NZ. 10 October 2013.
  21. ^ Withers, Joan (5 July 2016). "We're Mercury from 29 July 2016" (PDF). Letter to shareholders. Mighty River Power.
  22. ^ "Mercury buzzes in with new look, champions renewable energy". 29 July 2016. Retrieved 9 June 2020.
  23. ^ "Operating Statistics - Mercury NZ". Retrieved 20 July 2017.
  24. ^ "Mighty River Power lodges application for wind development at Puketoi" (Press release). Mighty River Power. 3 August 2011. Archived from the original on 4 October 2011.
  25. ^ "Mighty River gains consents for Puketoi wind farm" (Press release). Mighty River Power. 25 June 2012. Retrieved 25 June 2012.
  26. ^ a b c d "Mighty River Power Development Projects Update" (Press release). Mighty River Power. 13 June 2012. Archived from the original on 29 July 2012. Retrieved 29 July 2016.
  27. ^ "Mighty River Power takes direct control of geothermal interests in Chile and US-based EnergySource" (Press release). Mighty River Power. 15 February 2013. Archived from the original on 10 August 2014.
  28. ^ "Starship Children's Health | Supporting Our Community | Mercury".

External links[edit]