The Building Sustainability Index (BASIX) is a web-based planning tool that measures the potential performance of new residential dwellings against sustainability indices.

BASIX requires all new homes in NSW to use up to 40% less potable water and produce up to 40% fewer greenhouse gas emissions than the average home.

BASIX also applies to major alterations and additions to existing homes (over the value of $50,000) and swimming pools larger than 40,000 litres.

The BASIX energy target varies according to building type and location and the BASIX water target incorporates regional variations such as soil type, climate, rainfall and evaporation rates.

Each development application for a residential dwelling (a single dwelling or a multi-unit) must be submitted with a BASIX certificate.

A certificate is issued once a BASIX assessment has been satisfactorily completed, using the online tool:

The building applicant (eg architect, builder, owner builder) is responsible for completing the assessment, ensuring the BASIX commitments are clearly marked on the plans, and submitting the BASIX Certificate with the development application.

MidCoast Water Services does not administer BASIX, but we do have some responsibilities under the scheme.

We need to

  • Keep a copy of your BASIX certificate
  • Record the water efficient measures installed at the house
  • Check that the rainwater tank (if you have one) is not sited too close to a water or sewer main
  • Inspect all the plumbing work to make sure it meets the national plumbing standards

We will look at your BASIX Certificate when you bring your Local Development Application to MidCoast Water Services for its stamp.

For more information or to use the BASIX Tool, visit or phone the BASIX Help Line on 1300 650 908