NatHERS Explained · My Cool Home

    6
    7

    …not what you think.

    You've seen the rating everywhere. But that jump from 6 to 7 stars? It's not small — and it's definitely not obvious.

    Most people get this wrong

    WHAT IS NatHERS?

    A compliance tool — not a decision tool.

    NatHERS (the Nationwide House Energy Rating Scheme) rates how much energy a home needs to stay comfortable — on a scale of 0 to 10 stars. It was designed for builders and regulators to confirm a home meets minimum standards. It's a snapshot of the building's thermal shell — walls, roof, windows, floor.

    What it measures

    • Building envelope
    • Window orientation & glazing
    • Insulation values
    • Climate zone benchmarks
    • Thermal mass

    What it doesn't measure

    • How you actually live
    • Air leakage & draughts
    • Heating & cooling habits
    • Retrofitted upgrades
    • Real energy bills

    Two identical homes can perform completely differently. The rating doesn't know who lives inside them.

    THE CURVE

    The curve that changes everything

    Stars aren't equal.

    The gap between 3 and 6 stars is enormous. The gap between 9 and 10 is almost nothing. Where you are on the curve determines whether an upgrade is worth it.

    Tap a band to understand what it means

    8 – 8.5 stars — Sweet spot

    High performance without over-engineering. The best balance of comfort, cost, and carbon for most Australian homes. Mechanical heating and cooling become supplementary rather than essential.

    This is where most homeowners should aim. Beyond this point, each additional star costs significantly more for diminishing returns.

    "The sweet spot for most Australian homes sits around 8 to 8.5 stars — high performance, without over-engineering."

    THE BLACK BOX

    Same rating. Different reality.

    NatHERS assumes a standard household. But behaviour changes everything. Two homes with identical ratings can have wildly different comfort levels and energy bills.

    Home A

    7 ★
    • Blinds closed by 10am
    • Thermostat at 21°
    • Ceiling fans first
    • Opens up at night
    vs

    Home B

    7 ★
    • No shading, full sun
    • A/C runs at 18°
    • Heating left on overnight
    • Doors open in summer

    This is why a star rating alone isn't enough. Context, behaviour, and honest assessment matter just as much as the number.

    FIND YOUR RATING

    Now you know what it means.

    Here are three ways to find your home's rating — from official certificates through to a full comfort picture.

    Energy Rating Finder

    Search by address. Instant result if your home was previously assessed.

    RapidRate · CSIRO ML

    Get a quick estimate

    CSIRO machine learning estimate. Answer a few questions, get an indicative rating in minutes.

    Assessor · Certified

    Book a licensed assessor

    Official NatHERS certificate. Best for buying, selling or major works.

    Our pick
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    My Cool Home

    Yes, we're biased. You should be using My Cool Home.

    Your star rating in context — with a comfort profile, upgrade recommendations, and a clear picture of what's actually worth doing next. It's the whole picture, not just a number.

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    Understanding your home's energy rating

    Get your star rating in context — with comfort insights, upgrade recommendations, and a clear picture of what's worth doing next.

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