If you're building or renovating in New South Wales, there's one certificate you can't lodge a development application without: BASIX. The Building Sustainability Index is the NSW planning tool that makes sure new homes are water- and energy-efficient. Here's what it covers and how to get through it smoothly.
What is BASIX?
BASIX (the Building Sustainability Index) is a NSW Government planning requirement introduced to reduce the water and energy use of new residential buildings. Your design is assessed against set targets, and a BASIX Certificate is issued that must be lodged with your development application (DA) or complying development certificate (CDC).
The short version
In NSW, a BASIX Certificate is mandatory for new dwellings and many alterations and additions. No certificate, no approval.
The three things BASIX measures
Every BASIX assessment looks at three areas, each with its own target your design has to meet:
- Water — reducing potable water use through efficient fixtures, and often rainwater tanks or alternative water sources.
- Thermal comfort — how well the home stays comfortable, assessed through the building's fabric (insulation, glazing, orientation). This is closely aligned with NatHERS modelling.
- Energy — reducing greenhouse-gas-intensive energy use, factoring in appliances, hot water, lighting and solar.
When do you need a BASIX Certificate?
You'll generally need one for:
- All new dwellings — houses, townhouses, dual occupancies and apartments.
- Alterations and additions above a certain value threshold.
- Swimming pools and spas above a set size.
NSW is also the one state where new homes are assessed through BASIX rather than a standalone NatHERS certificate — although the thermal-comfort component uses the same underlying energy modelling, so getting the fabric right still matters just as much.
How the targets have tightened
BASIX targets have been progressively lifted to bring NSW into line with national energy-efficiency goals — most notably to align the thermal-comfort and energy scores with the higher standards introduced in NCC 2022. In practice that means newer BASIX assessments expect better-performing building fabric and more efficient systems than a few years ago.
BASIX targets and thresholds are set by the NSW Government and updated from time to time — always confirm the current requirements on the NSW Planning Portal or with your assessor before finalising a design.
How to make BASIX painless
The smoothest BASIX outcomes come from thinking about it early:
- Orientation and glazing — the biggest levers on the thermal-comfort score, and free if planned from the start.
- Efficient fixtures and hot water — easy wins on the water and energy scores.
- Solar — rooftop PV is often the simplest way to lift the energy score.
- Assess before you lodge — running BASIX early means no nasty surprises at DA stage.
Lodging a NSW project soon?
We prepare BASIX Certificates for new dwellings, alterations and multi-unit developments — assessed, optimised and ready for your DA. Send us your plans for a fast quote.
BASIX doesn't have to be a hurdle — handled early, it simply confirms the sensible, efficient choices you'd want to make anyway. If you'd like it taken care of for your NSW project, our accredited assessors are happy to help.
