A $500 million gas-fired power station planned for the shores of Kaipara Harbour could delay the construction of transmission lines from Waikato to South Auckland.
State-owned Genesis Energy has selected an 18ha block of land between Helensville and Kaukapakapa for its station, which could be generating power by the summer
of 2008-2009.
A new station could mean the need for giant new pylons carrying lines through the Waikato would be delayed beyond the 2010 deadline.
Transpower spokesman Chris Roberts said: "If more generation is available from 2010 from whatever source, then the time when the existing transmission lines reach capacity may be pushed back a number of years."
The power plant could also affect the economics of a plan by fellow state-owned enterprise Mighty River Power to fire the mothballed Marsden B power station with coal.
Mighty River has been given consent to open the station, but is still analysing conditions imposed to see if they affect the plan's viability.
A new, more efficient power station north of Auckland could make Marsden B uneconomic.
Genesis has paid for an option on Kaipara land and will buy it if it receives resource consent for the station and builds within 24 months.
The natural gas-fired station would initially generate 240 megawatts of power.
