Home Energy Rating
Does a Home Energy Rating Provide a Star Rating?
A home energy rating may provide a star rating, but the star rating is only one part of the wider performance picture.
For many homeowners, the idea of a star rating is familiar because NatHERS has long used stars to describe the thermal performance of new homes. As NatHERS expands into existing homes, star rating language is also becoming relevant to established dwellings.
The key is to understand what the star rating does, what it does not measure, and how it differs from broader whole-of-home energy performance.
Quick Answer
A home energy rating can include a star rating, but the exact output depends on the assessment pathway.
Under NatHERS, homes can receive a thermal star rating from 0 to 10. A higher star rating generally means the home is expected to be more comfortable and cheaper to keep comfortable, because it should need less heating and cooling.
For existing homes, the rating may also sit alongside broader home energy performance information. This can include whole-of-home energy considerations such as heating and cooling systems, hot water, lighting, appliances, solar PV and batteries.
The star rating is useful, but it should not be treated as the only thing that matters. A home may also need practical upgrade advice, system review and careful interpretation of what the rating means for comfort, running costs and future improvements.
What does the star rating mean?
The NatHERS star rating describes the thermal performance of a home. It helps explain how much heating and cooling the dwelling is likely to need to remain comfortable in its climate.
A higher star rating generally means the home is better at staying comfortable with less energy for heating and cooling. A lower star rating generally means the home may be more expensive or difficult to keep comfortable.
For an existing home, this can be useful because it gives the homeowner a clearer performance signal than simply saying the home feels hot, cold or expensive to run.
What influences the star rating?
The thermal star rating is influenced by the way the home is designed, built and exposed to its climate.
Key factors may include:
- climate zone
- orientation
- dwelling layout
- roof, wall and floor construction
- ceiling, wall and floor insulation
- window size and placement
- glazing type
- external shading
- thermal mass
- air movement and ventilation
- draughts or air leakage
- renovation and extension history
In existing homes, some of these details may be easy to identify. Others may need to be confirmed through plans, site observations, photos, homeowner information or assessment assumptions.
Is the star rating the same as whole-of-home performance?
No. The thermal star rating and whole-of-home performance are related, but they are not the same thing.
The thermal star rating focuses on the building’s heating and cooling needs. It is mainly about how well the dwelling itself manages heat gain, heat loss and thermal comfort.
Whole-of-home performance may also consider major energy systems and generation, such as hot water, heating and cooling systems, lighting, appliances, solar PV and batteries. This gives a broader view of energy use across the home.
Why the star rating is not the whole answer
A star rating is a useful summary, but it does not explain everything on its own.
For example, two homes may have similar thermal ratings but very different hot water systems, appliance loads, solar systems or battery storage. One may have strong building fabric but inefficient systems. Another may have solar panels but still overheat because of poor shading or glazing.
This is why a home energy rating should be interpreted with the wider assessment information, not only the star number.
Is an existing home star rating the same as a new home rating?
The rating language may be similar, but the assessment context is different.
A new home NatHERS assessment usually rates a proposed design before it is built. It is commonly used for compliance and design-stage decision-making.
An existing home rating assesses a dwelling that already exists. It must respond to real construction, previous renovations, installed systems, missing documentation and the current condition of the home.
For a detailed comparison, see NatHERS Existing Homes vs New Home NatHERS Assessments.
Does a 7 Star requirement apply to existing homes?
The 7 Star conversation is mainly connected to new-home energy efficiency standards under the National Construction Code and state implementation.
Existing home ratings are different. They help assess current performance and identify possible upgrades, but they should not be confused with a new-home compliance requirement.
A homeowner may still want to improve the rating of an existing home, but the assessment should be understood as a performance and improvement pathway, not simply a new-build compliance test.
What appears on a Home Energy Rating Certificate?
A Home Energy Rating Certificate may show the home’s assessed energy performance and provide information that can help guide comfort and upgrade decisions.
The exact certificate format can depend on the assessment pathway and rollout stage. In the NatHERS existing homes trial, participating households received a trial certificate that included a star rating out of 10 and a home energy rating out of 100.
For homeowners, the most useful approach is to treat the certificate as a starting point for understanding performance, not as a replacement for practical assessment advice.
Can the rating help identify upgrades?
Yes. A rating can help identify where an existing home may be improved.
Possible upgrade areas may include:
- ceiling, wall or floor insulation
- draught sealing
- window and glazing improvements
- external shading
- heating and cooling replacement
- hot water upgrades
- solar PV and battery systems
- ventilation improvements
- staged renovation measures
The important question is sequencing. A good assessment can help a homeowner understand which measures should be considered first, rather than treating every upgrade as equal.
Does a higher star rating guarantee lower bills?
A higher star rating generally indicates that the home should need less heating and cooling to remain comfortable. This can support lower running costs, especially when compared with a similar home in the same climate and usage pattern.
However, energy bills are also affected by household behaviour, tariffs, occupancy, appliances, pool equipment, work-from-home patterns, thermostat settings and how systems are used.
This is why the rating should be read as performance information, not as a guarantee of a specific bill amount.
What information is needed to produce a rating?
To produce a rating, the assessor needs enough information about the dwelling and its systems. For existing homes, this may include property details, available plans, site data, photos, renovation history, insulation details and system information.
Useful preparation may include:
- property address
- available plans or drawings
- renovation history
- photos of the home
- known insulation details
- window and glazing information
- heating and cooling system details
- hot water system details
- solar or battery information
- known comfort issues
For a practical checklist, see What Information Do You Need for a Home Energy Rating?
How the star rating fits into the existing homes pathway
As NatHERS expands into existing homes, star ratings help bring a familiar performance language into established dwellings.
This can help homeowners, buyers, sellers, landlords and property professionals understand a home’s performance more clearly. It may also support future disclosure conversations as rating pathways continue to develop.
For more context, see What Is NatHERS Existing Homes?
FAQs
Does a home energy rating provide a star rating?
A home energy rating may provide a star rating, depending on the assessment pathway. Under NatHERS, homes can receive a thermal star rating from 0 to 10, where a higher rating generally means the home is more comfortable and cheaper to run.
What does the NatHERS star rating mean?
The NatHERS thermal star rating describes how well the home performs thermally. It reflects how much heating and cooling the home is likely to need to remain comfortable, based on features such as layout, orientation, insulation, windows, shading and climate.
Is the star rating the same as the whole home energy rating?
No. The thermal star rating and whole-of-home energy performance are related but not the same. The star rating focuses on thermal performance, while whole-of-home performance may also consider appliances, hot water, solar, batteries and other energy uses.
Does a higher star rating mean lower energy bills?
A higher star rating generally indicates a home should need less heating and cooling to remain comfortable. However, actual energy bills also depend on household behaviour, tariffs, occupancy, appliances and system use.
Can an existing home improve its star rating?
An existing home may be able to improve its rating through upgrades such as insulation, draught sealing, window improvements, shading, efficient heating and cooling, hot water upgrades, solar or batteries. The best sequence depends on the home.
Is a 7 Star rating required for existing homes?
7 Star requirements are mainly connected to new-home energy efficiency standards under the National Construction Code. Existing home ratings help assess current performance and upgrade potential, but they should not be confused with new-home compliance requirements.
Rating Pathway Advice
Need to understand what rating output applies?
Certified Energy can help explain what rating output applies to your assessment pathway.
