NatHERS (Nationwide House Energy Rating Scheme) is the standard method used in Australia to assess the thermal performance of residential buildings.
It measures how well a home maintains comfortable indoor temperatures throughout the year — based on its design, materials and construction.
This article explains how NatHERS star ratings work, what the 0–10 scale represents, and how ratings are calculated in practice.
What a NatHERS rating measures
A NatHERS rating evaluates how much heating and cooling a home requires to stay comfortable.
The assessment focuses on the building fabric, including:
- Orientation and layout
- Insulation levels
- Window size, type and placement
- Shading and ventilation
- Construction materials
It does not include appliances, solar systems, or occupant behaviour.
A higher rating means the home performs better passively, reducing the need for mechanical heating and cooling.
How the 0–10 star scale works
NatHERS uses a star rating scale from 0 to 10:
- 0 stars → very poor thermal performance
- 6 stars → previous minimum standard (pre-NCC 2022)
- 7 stars → current minimum requirement for most new homes
- 10 stars → near self-regulating internal comfort
The higher the star rating, the less energy is required to maintain comfortable indoor temperatures.
How NatHERS ratings are calculated
NatHERS assessments are completed by accredited assessors using approved thermal modelling software.
The process typically involves four steps:
1. Build a simulation model
The assessor inputs detailed information about the dwelling, including room layouts, materials, insulation, glazing, and orientation.
2. Simulate internal temperatures
The software models how the home responds to local climate conditions across the year, hour by hour.
3. Calculate heating and cooling demand
The model determines how much heating or cooling would be needed to maintain comfortable conditions.
4. Convert results into a star rating
The total annual heating and cooling load is converted into a rating out of 10 stars.
What affects your NatHERS rating
Small design decisions can have a significant impact on your final rating.
Key factors include:
- Building orientation relative to the sun
- Window placement and glazing performance
- Insulation levels and thermal mass
- Shading devices and eaves
- Cross-ventilation and airflow
Because of this, NatHERS assessments are most effective when considered early in the design process.
Why this matters for your project
Under the National Construction Code (NCC 2022), most new homes are required to achieve a minimum 7-star NatHERS rating, alongside Whole of Home energy requirements.
Understanding how ratings are calculated helps you:
- Avoid unnecessary redesign
- Make informed design decisions early
- Achieve compliance more efficiently
- Improve long-term comfort and performance
Final note
NatHERS is not just a compliance tool — it is a way to test how a home will perform before it is built.
When used early, it supports better design outcomes and more efficient buildings.
If you’re looking to understand requirements, costs and timelines:
