It could soon be easier on the environment to have a shower or use the toilet in Auckland.

That's because of a target for the city's two major wastewater treatment plants to become electricity neutral by 2025.

Watercare plans to run its Rosedale and Mangere plants entirely on biogas, a byproduct of the wastewater treatment process.

Currently biogas powers engines that meet 56 per cent of the electricity needs of both plants.

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Watercare chief executive Raveen Jaduram said Watercare is committed to integrating sustainability into all aspects of the business.

"If our Mangere plant becomes self-sufficient in terms of generating electricity, we will have achieved a world-first for a plant of its size," he said.

Every day, Watercare supplies 326 million litres of drinking water to 1.4 million people across Auckland, and treats 400 million litres of wastewater. Providing these services requires 167 gigawatt-hours (GWh) of electricity annually, enough to power 22,000 homes.

On Tuesday as a first step, Watercare is due to sign a three-year agreement with the Energy Efficiency and Conservation Authority (EECA), which will see the two organisations working together and sharing expertise to meet an interim energy savings target of 8GWh and 1300 tonnes of carbon emissions by 2019.

The agreement will involve an assessment of Watercare's energy-intensive assets - including plants, networks, pump stations and offices - to identify areas where efficiency gains can be made.

Mr Jaduram said: "Joining the minds of our highly skilled workforce with the forward thinkers at EECA will enable us to identify the most effective ways for us to achieve this efficiency by 2025, an ambitious goal that we are determined to reach."

EECA chief executive Mike Underhill said Watercare is a New Zealand company showing leadership to the world in terms of energy ambition.

"This is a massive undertaking and will place Watercare at the forefront worldwide as an energy-neutral wastewater plant. Watercare's ambition and commitment is to be applauded and EECA looks forward to supporting them on their energy journey." ends