If you are planning a new home in Australia, you will hear a lot about star ratings. Your builder or designer will mention NatHERS early on. The rating affects how your plans get approved. It also shapes how comfortable the house feels once you move in.
This guide explains what the rating measures and why the minimum is now 7 stars. It also covers the design choices that tend to move the score. None of it is hard to follow once you know what the assessor is looking at.
What NatHERS actually measures
NatHERS stands for the Nationwide House Energy Rating Scheme. A NatHERS star rating is out of 10 and measures the thermal performance of a home. In plain terms, it estimates how much heating and cooling the house will need to stay comfortable. The higher the number, the less energy the home should need.
The star rating looks at the design, the orientation, the building materials and the local climate. It does not include how efficient your appliances are. A well designed home with poor appliances can still score well on stars. That is why there is now a second rating as well.
The Whole of Home rating
The Whole of Home rating covers the major energy use in the house. According to the NatHERS guide to energy assessments for new homes, this includes hot water, heating and cooling systems, pool and spa equipment and lighting. It also counts plug in appliances and any onsite solar and battery storage. The result is an estimate of how much energy the home should use each year.
Why the minimum is now 7 stars
The 2022 National Construction Code raised the bar for new houses and apartments. New homes now need to reach at least 7 stars under NatHERS, up from the old minimum of 6 stars. The same code brought in the Whole of Home energy budget. The NatHERS certificate is one way to show your plans meet these rules.
The gain from that extra star is real. Sustainability Victoria says a 7 star home needs about 20 to 25 per cent less heating and cooling energy than a 6 star home. That means a more comfortable house and lower running costs. It also gives better protection during heatwaves and cold snaps.
States and territories differ
The code is national, but each state and territory adopts it in its own way and on its own timeline. Victoria, for example, brought the 2022 changes in from May 2024. Some places also have their own variations or extra rules. NatHERS itself advises checking the specific building requirements in your state or territory before you lock in a design.
In Victoria, the guide to the 7 star new home standards says detached and semi detached houses need a Whole of Home score of at least 60. Apartments need at least 50. Rooftop solar can offset part of the energy use counted in that budget. Other states may set things out differently, so ask your assessor what applies to your block.
Who does the assessment
The rating is done by a NatHERS Accredited Assessor. Assessors complete training and work under a code of conduct with quality checks. They review your plans and issue a NatHERS Certificate. That certificate shows both the star rating and the Whole of Home rating.
NatHERS suggests bringing an assessor in early, while the design can still change. A few small changes at the drawing stage are far cheaper than fixing a poor score later. Sustainability Victoria makes the same point about retrofitting. Changing a finished home is harder and more expensive than building it well from the start.
Design choices that move the rating
Getting to 7 stars often needs little extra cost according to Sustainability Victoria. Most of the gain comes from good orientation, shading, insulation and glazing. A block with poor orientation may need more work in other areas. The NatHERS tips for builders point to a handful of common levers:
- Orientation and placing the plan on the block to suit the local climate
- Better glazing, with window sizes and shading that suit the site
- More internal doors so living zones can be closed off
- Extra insulation in walls, floors, ceilings and around slab edges
- Ceiling fans in living areas and bedrooms
- Lighter roof colours in warmer climates
- Fewer downlights and skylights cutting through the ceiling insulation
Windows and glazing
Windows are often where a design gains or loses the most ground. NatHERS notes that double and triple glazing are now cheaper and easier to get than they once were. Default window options in the rating software tend to give a lower result. If you want to understand the basics, our piece on how double glazing works covers how the extra layer of glass slows heat transfer.
Zoning, layout and storage
Zoning simply means being able to close off parts of the house. A door at the end of a hallway or the bottom of a stair can make a measurable difference. Rooms used less often, such as a media room, can be shut off from the main living area. Work through storage ideas for your new home at the same time. Built in storage often sits along those same internal walls.
Shade from the garden
Shade does not have to come only from eaves and awnings. Trees, pergolas and planting can help shade walls and windows in summer. Planting takes years to grow, so treat it as a bonus on top of a sound design. Over time, good principles of landscape design can help keep a home cooler day to day.
What about renovations and existing homes
The 7 star rule applies to new homes and apartments. A major renovation can still use a NatHERS assessment to guide insulation, glazing and appliance choices. NatHERS has started rating existing homes, at first through a small group of trained assessors. During the changeover, the voluntary NatHERS endorsed Residential Efficiency Scorecard is still available for existing houses.
If you are improving an older home to sell, energy features can be a selling point. NatHERS notes that energy efficient homes may have a higher resale value. Our article on renovating for profit in Perth looks at where renovation money tends to pay off. Insulation and better windows are often worth weighing up alongside kitchens and bathrooms.
Frequently asked questions
Is a NatHERS rating the same as an appliance energy label?
No, they measure different things. The star rating looks at the building shell and how much heating and cooling it needs. The Whole of Home rating then adds the home’s appliances, such as hot water, heating, cooling, lighting and solar.
Can I build a home below 7 stars?
NatHERS notes that houses with a compliant outdoor living area in NCC climate zones 1 and 2 may be allowed 6 or 6.5 stars. This allowance is set out in the NCC energy efficiency rules. Other exceptions and pathways vary, so check with your assessor and local building surveyor.
When should I get the assessment done?
The earlier the better. An assessor working from early drawings can suggest changes before they become costly. Leaving it until the plans are final often limits your options to more insulation or dearer windows.
Does solar count in the rating?
Solar does not change the star rating, which only covers heating and cooling needs. It does count in the Whole of Home rating, which includes onsite generation and batteries. In Victoria, rooftop solar can offset part of the annual energy budget.
Building rules and energy requirements differ between states and territories and change over time. Always check the current requirements with your local building authority or an accredited assessor before you finalise your plans.
