NatHERS vs BASIX: What’s the Difference?
NatHERS rates your home’s thermal performance; BASIX is the mandatory NSW certificate covering energy, water and thermal comfort. Most new homes need both.
“Do I need NatHERS or BASIX?” is one of the most common questions we get. The short answer for NSW: usually both. Here’s how they fit together.
What is BASIX?
BASIX (Building Sustainability Index) is the mandatory NSW certificate for residential development. It sets targets across three areas – energy, thermal comfort and water – and you can’t get development approval without it.
What is NatHERS?
NatHERS (Nationwide House Energy Rating Scheme) is the national thermal performance rating for the building fabric. It produces a star rating out of 10 based on how much heating and cooling energy the home needs.
How they relate
They’re not competing – they’re layered. In NSW, BASIX is the umbrella certificate, and a NatHERS assessment is the most common way to satisfy the thermal comfort part of BASIX.
| NatHERS | BASIX | |
|---|---|---|
| Scope | Thermal performance of the building fabric | Energy, thermal comfort & water |
| Output | Star rating (out of 10) + certificate | BASIX Certificate with commitments |
| Where it applies | Nationwide | New South Wales only |
| Mandatory in NSW? | As part of BASIX compliance | Yes – always |
So which do I need?
- Building a new home in NSW? You need a BASIX Certificate, and almost always a NatHERS assessment to meet the thermal comfort target.
- Outside NSW? BASIX doesn’t apply, but you’ll still need a NatHERS rating to meet NCC thermal requirements.
- Doing a small renovation? BASIX may apply depending on cost; we can confirm quickly.
The simplest approach
Prepare both together. When the same team handles your NatHERS and BASIX, the documents align perfectly, there’s no double-handling, and it’s usually cheaper than engaging two providers.
Frequently asked questions
Can I have BASIX without NatHERS? BASIX offers an alternative “DIY” thermal pathway, but for most homes a NatHERS assessment gives a better, more reliable result.
Do the certificates expire? A BASIX Certificate is valid 3 months for lodgement; NatHERS certificates are tied to the assessed design.
Not sure what your project needs? Send us your plans and we’ll tell you exactly what applies.
BASIX & NatHERS specialists, a division of Contrive Consultants. We help NSW homeowners and builders achieve energy-efficient, compliant homes.