NatHERS Star Rating Explained

What Is a NatHERS Star Rating?

The Nationwide House Energy Rating Scheme (NatHERS) is Australia's official system for rating the energy efficiency of homes. Developed by CSIRO and administered by the Australian Government, it measures how much energy a home needs for heating and cooling on a scale from 0 to 10 stars.

Think of it like a fuel efficiency rating for your house. A higher star rating means your home needs less energy to stay comfortable — which translates directly to lower energy bills, reduced emissions, and better comfort year-round.

Key fact: A 10-star home needs virtually no artificial heating or cooling. A 0-star home has the thermal performance of living outdoors.

How Are Ratings Calculated?

NatHERS ratings are calculated by accredited assessors using CSIRO-approved software (such as FirstRate5, BERS Pro, or AccuRate). The software creates a thermal model of your home and simulates its performance against your local climate zone. The result is documented in an official NatHERS certificate.

The key factors modelled include:

The result is expressed in MJ/m²/year (megajoules per square metre per year) — the predicted energy needed for heating and cooling. This number is then converted to a star rating. Lower MJ/m²/yr = higher stars.

NCC 2022: The 7-Star Minimum

The National Construction Code 2022 (NCC 2022) raised the minimum NatHERS requirement for new homes from 6 stars to 7 stars. This applies to:

• • All new residential construction (houses, apartments, townhouses)
• • Major renovations that trigger building approval
• • Extensions and additions in most states

Some states have additional requirements. For example, NSW uses BASIX alongside NatHERS, while Victoria's VEU program provides incentives for exceeding minimums.

What Each Extra Star Saves You

Each additional star represents a meaningful reduction in energy consumption and bills:

• Per star improvement: Approximately 10–15% reduction in heating/cooling energy
• 5-star → 7-star: Saves approximately $500–$1,000/year in energy bills
• 3-star → 7-star: Saves approximately $1,000–$2,000/year
• Property value: Each star adds an estimated 1–3% to property value

Learn about assessment costs → The investment in both the assessment and improvements typically pays for itself within 2–5 years.

NatHERS Climate Zones

Australia is divided into 69 NatHERS climate zones, each with unique weather data. Your climate zone significantly affects your star rating because the same house design will perform differently in Darwin's tropics versus Hobart's cool climate.

This means a home optimised for Brisbane's subtropical climate (focused on cooling and ventilation) will need very different strategies than one in Melbourne (focused on heating and insulation).

Find assessors who understand your local climate zone: