If you’re building in NSW, your certifier or council will ask for a BASIX certificate. Your builder might mention a NatHERS rating or “stars”. They’re related, but they’re not the same thing, and a new home usually needs both.
The short version
| BASIX | NatHERS | |
|---|---|---|
| What it is | NSW sustainability standard for housing | National rating of a home’s thermal performance |
| Where it applies | NSW only | Australia-wide |
| Measures | Water, energy and thermal performance | Heating and cooling energy needed (thermal only) |
| Result | Pass or fail against targets | 0 to 10 stars, plus heating and cooling loads |
| Issued by | NSW Planning Portal | Accredited assessor through the NatHERS certificate system |
| Needed for | DA or CDC for new dwellings, alterations over $50k, pools over 40,000 L | BASIX simulation method; NCC compliance in other states |
What BASIX covers
BASIX, the Building Sustainability Index, is a NSW planning requirement. It has three sections:
- Water: fixtures, rainwater tanks, landscaping and pools, measured against a potable water target for your area.
- Energy: hot water, heating and cooling, cooking, lighting and solar, measured as greenhouse emissions.
- Thermal performance: how well the building fabric keeps heat in or out.
BASIX is completed on the NSW Planning Portal, and the certificate lists commitments that must appear on the plans and be built.
What NatHERS covers
NatHERS, the Nationwide House Energy Rating Scheme, only deals with thermal performance. An accredited assessor models the dwelling in NatHERS software, including walls, windows, floors, roof, orientation and shading. The software simulates a year of local weather to work out how much heating and cooling it would need.
The result is a star rating from 0 to 10, based on the loads for your climate zone. A higher rating means a more comfortable home that is cheaper to run.
How they connect in NSW
This is where the confusion comes from. The BASIX thermal section can be completed two ways:
- DIY method: you enter construction and glazing details and BASIX applies fixed rules. No NatHERS rating is involved. It suits simpler designs and most renovations.
- Simulation method: an accredited assessor runs a NatHERS simulation, and the heating and cooling loads are entered into BASIX. The dwelling must meet heating and cooling caps. Since October 2023 the standard is roughly equivalent to an average of 7 stars.
So on the simulation method, the NatHERS certificate is the evidence behind the thermal section of the BASIX certificate. Both certificates, plus plans stamped by the assessor, go to the certifier.
Outside NSW, the NCC requires new homes to reach 7 stars under NatHERS, plus a whole-of-home energy rating. NSW has its own settings through BASIX instead, which is why a NSW house doesn’t get assessed against the national 7-star rule directly.
Which do you need?
- New house, granny flat or duplex: BASIX certificate, usually with a NatHERS simulation behind it.
- Alterations and additions over $50,000: BASIX certificate, usually on the DIY thermal method.
- New pool or spa of 40,000 L or more: BASIX certificate.
- Townhouses and apartments: BASIX for the development, with a NatHERS rating for each unit.
- Commercial buildings: neither. Those fall under Section J of the NCC.
Why it pays to do them together
When the same assessor does the NatHERS model and the BASIX certificate, the thermal inputs, commitments and stamped plans all match. That’s what certifiers check. Mismatches between separate consultants are one of the most common reasons a CC or occupation certificate gets held up.
Need BASIX and NatHERS for a new home?
Assessments prepared from your drawings, anywhere in NSW. Turnaround is confirmed in your quote and starts once all required information is received.
General information only, current at the date above. Requirements change and every project is different, so confirm the rules that apply to your project with your certifier or council.