A 480-megawatt power station planned by Genesis Energy could pollute the area and may not alleviate supply shortages, according to concerned residents.
The State-owned enterprise says the gas-fired plant is needed to cope with population growth and help rectify shortcomings in the current power supply network.
Genesis wants to build the plant in the next 35 years, and its application is before commissioners from the Auckland Regional and Rodney District councils.
But Neville Miller, who chairs the Kaukapapa area residents and ratepayers association, says many locals in the district are fearful about any emissions from the site.
Mr Miller says residents in the district depend on tank water that is collected from roof run-off.
"Anything which affects the quality of water - any emissions or particular matter coming onto people's roofs and so on is of great concern to us."
Genesis says a gas-fired plant would provide a firm and controllable electricity supply and the chosen site is close to infrastructure and the growing demand for power.