What is a NatHERS star rating?
Written by a registered architect for Dudils.
A NatHERS star rating scores a home from 0 to 10 stars on how much heating and cooling its design needs to stay comfortable, and more stars means less. NatHERS, the Nationwide House Energy Rating Scheme, rates the shell of the house: the walls, roof, floor and windows, and which way they face on the block. Search an address on the BASIX lookup to see a home's rating where the council published its certificate.
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What do the stars mean?
Each star stands for a lower modelled heating and cooling load, in megajoules per square metre of floor each year. A home with close to 0 stars gives almost no protection from heat or cold, and a 10 star home needs little or no heating or cooling. The scale is set for each climate zone, so the same number of stars allows a different load in Sydney than in Canberra.
What star rating does a new home in NSW need?
Most new homes approved in NSW since 1 October 2023 need about 7 stars, up from an average of 5.5 to 6 stars before. That is when BASIX raised its thermal comfort standard. Homes in climate zones 9, 10 and 11, in north eastern NSW, kept the earlier standard, and BASIX sets the exact heating and cooling limits for each location.
What is the difference between NatHERS and BASIX?
NatHERS rates one thing, the shell of the house, while BASIX is the NSW approval requirement that covers water, energy and thermal comfort together. A NatHERS assessment is one of the ways to pass the thermal comfort part of BASIX, so many NSW homes have both certificates, and the BASIX certificate quotes the NatHERS heating and cooling loads. The BASIX certificate guide covers the rest of what BASIX asks for.
Does a higher star rating mean lower power bills?
For heating and cooling, usually yes, but not for the rest of the bill. The rating models the shell only, so the hot water system, lighting, appliances, solar panels and how the household lives are outside it. BASIX covers some of those through its energy score.
How do I find my home's NatHERS rating?
Read it off the home's NatHERS certificate, which lists the stars, the heating and cooling loads and the construction the rating assumed. For a house approved by development application the certificate is often on the council's DA tracker, and the BASIX lookup reads it for the councils we cover. Recent certificates carry a link or QR code that opens them on the rating software provider's website, and the owner's handover documents should hold a copy.
Can an older house get a NatHERS rating?
Yes. A NatHERS accredited assessor can rate an existing home from its plans and measurements. For an existing home the government backed Residential Efficiency Scorecard is another option, and it looks at the appliances as well as the shell.
What else do people ask?
What does a 7 star rating mean?
It means the design's modelled heating and cooling load is low enough to reach 7 on the scale for its climate zone. That is the level most new NSW homes have had to reach since 1 October 2023.
Does orientation change the star rating?
Yes. The rating models the house on its real block, so the same design can rate differently facing north or south, because north facing living room windows take in winter sun. A rating belongs to a house on a particular site, not to a plan.
Where does this information come from?
This guide explains how BASIX and NatHERS work in general. A certificate records the design that was approved, and your home may differ from it. Nothing on this page replaces advice from your certifier, engineer, lawyer or your own designer.