NatHERS Star Ratings
A NatHERS star rating gives a clearer indication of how well a home is expected to stay comfortable in its climate. It is not just a compliance number. It reflects the thermal performance of the building fabric.
A NatHERS star rating measures the predicted thermal performance of a home on a scale from 0 to 10 stars. The rating estimates how much heating and cooling the home may need to remain comfortable, based on the design, construction, materials and local climate. A higher star rating generally means the home should need less heating and cooling.
A NatHERS star rating tells you how well the home’s design is expected to manage heat and cold. It is a measure of thermal performance, which means it focuses on how the home responds to climate before relying on mechanical heating or cooling.
The rating is calculated using accredited NatHERS software. The software models the proposed home and estimates the amount of heating and cooling needed to keep indoor conditions comfortable across the year.
This is why two homes with similar floor areas can receive different star ratings. A home’s orientation, glazing, insulation, shading, construction materials, roof colour and climate zone can all affect the final result.
The NatHERS thermal star rating scale runs from 0 to 10 stars. A lower star rating means the home is expected to need more heating and cooling to remain comfortable. A higher star rating means the building fabric is doing more work to moderate temperature naturally.
Lower star rating: the home may be harder to keep comfortable and may need more heating or cooling.
Mid-range star rating: the home has some thermal performance measures, but may still rely heavily on heating and cooling in some seasons.
Higher star rating: the home is expected to remain comfortable more easily because orientation, insulation, glazing, shading and construction details are working together more effectively.
The star rating does not mean every room will always feel perfect in every condition. It is a modelling outcome that helps compare the thermal performance of residential designs in a consistent way.
It is easy to think of NatHERS as an energy rating only. In practice, the rating is closely connected to comfort. A home that needs less heating and cooling to stay comfortable is usually better at slowing heat loss in winter and reducing unwanted heat gain in summer.
This can change how a home feels day to day. Better thermal performance can support more stable indoor temperatures, less reliance on mechanical systems and a more resilient home during hot or cold weather.
Energy bills still depend on how people use the home, what systems are installed and what energy source is used. But the star rating helps show whether the design itself is working with the climate or fighting against it.
A NatHERS star rating is not determined by one product or one design feature. It is shaped by the way the whole building fabric performs as a system.
• Orientation and solar exposure
• Window size, placement, frame type and glazing performance
• Wall, ceiling, roof and floor insulation
• Eaves, awnings, balconies and other shading elements
• Construction materials and thermal mass
• Roof colour and external surface properties
• Local climate zone and seasonal temperature patterns
Because these factors interact, improving a rating is often about balance. More insulation may help, but glazing, shading and orientation can also have a major influence. In some designs, one poorly considered feature can offset several good decisions elsewhere.
For new residential projects, a NatHERS star rating is often used as part of the energy efficiency compliance pathway. The required rating depends on the project type, location, approval pathway and applicable requirements at the time of assessment.
In NSW, NatHERS is commonly considered alongside BASIX. Under current residential performance settings, a thermal star rating may also sit beside Whole of Home, which looks at major energy uses and onsite generation rather than only the building fabric.
This is why it is helpful to understand what the NatHERS star rating does and does not measure. It tells you about thermal performance. It does not, by itself, describe the full operational energy profile of the home.
NatHERS thermal star rating: focuses on heating and cooling needs created by the home’s design and building fabric.
Whole of Home: considers broader energy use, including appliances, hot water, heating and cooling systems, solar and batteries where applicable.
Australian homes experience very different climate conditions depending on location. A design approach that supports a strong NatHERS result in a cooler climate may not be the right strategy in a hot, humid or hot dry climate.
For this reason, the star rating should be understood in context. A good rating is not just about adding more products to a design. It is about making the home respond better to its site, orientation and local climate.
The most useful time to think about the star rating is before the design is locked in. Early attention to window placement, shading, insulation and building fabric details can make the rating easier to achieve and the home more comfortable to live in.
Certified Energy provides NatHERS assessments for Australian residential projects, including new homes, townhouses and multi residential developments. Our team reviews the project documentation, models the proposed design and helps project teams understand how the star rating relates to thermal performance and compliance.
Where a project needs a specific pathway, we can help connect the rating with related requirements such as 7 Star Rating, 6 Star NatHERS, BASIX and Whole of Home.
For a broader explanation of NatHERS and residential thermal performance, visit our NatHERS Knowledge Hub.
A NatHERS star rating shows the predicted thermal performance of a home. It indicates how much heating and cooling the home is likely to need to remain comfortable in its local climate.
Is a higher NatHERS star rating better?Generally, yes. A higher NatHERS star rating means the home is expected to need less heating and cooling to remain comfortable. The right design strategy still depends on the climate, site and project requirements.
Does the NatHERS star rating include appliances?The thermal star rating focuses on the building fabric and heating and cooling needs. Appliances, hot water, solar and batteries are considered through Whole of Home where that requirement applies.
Can two homes with the same star rating feel different?Yes. The star rating is a useful performance indicator, but comfort can still be influenced by room layout, ventilation, shading, occupant behaviour, heating and cooling systems and how the home is used day to day.
What affects a NatHERS star rating?The rating can be affected by orientation, glazing, insulation, shading, roof colour, floor construction, wall and roof materials, thermal mass and local climate conditions.