Star rating scale overview

NatHERS house ratings use computer simulations to determine the potential thermal comfort of Australian homes on a scale of zero to 10 stars. The more stars, the less likely the occupants will need cooling or heating to stay comfortable.

How are the stars determined?

7 star rating

A range for star ratings, called a 'star band', is set for each climate zone taking into account the extremes of the local weather conditions. Each star band set allows for a comparison of buildings within and between climate zones and is based on the maximum energy consumption per unit area (MJ/m2) loads for each half-star level.

Houses with higher star levels are considered more thermally comfortable than those of lower star levels with those rated at 10 stars considered thermally comfortable without the need for artificial heating and cooling.

Additional star bands are created when new climate zones are added to NatHERS.

View the NatHERS star bands [PDF 122 KB]

What do the stars mean?

A zero star rating means the building shell does practically nothing to reduce the discomfort of hot or cold weather. A six star rating indicates good, but not outstanding, thermal performance. Occupants of a 10 star rated home are unlikely to need any artificial cooling or heating.

What is rated?

A house can be rated before or after it is built. The rating depends on:

  • the layout of the home
  • the construction of its roof, walls, windows and floor
  • the orientation of windows and shading to the sun's path and local breezes
  • how well these suit the local climate.

Energy consumption by hot water systems, lights or household appliances is not considered in the rating because these fittings are usually replaced several times during the life of the building.

Typical ratings

Houses built in 1990 averaged about one star on the NatHERS scale. Before the introduction of national energy efficiency regulations for houses in 2003, less than one per cent of Australian houses achieved six stars.

Many well designed houses are now being built that are rated at seven stars or more. Examples are available on the Your Home website.

Want to know more?

If you want to learn more about how NatHERS star ratings are calculated using NatHERS Accredited Software, please see How NatHERS Star Ratings are calculated.