If you have spent any time around new builds, renovations or display homes lately, you will have heard someone mention star ratings. Seven stars, to be specific. It gets said with the confidence of a phrase everyone is expected to understand, and almost nobody stops to explain it. So let’s fix that.

The short version

NatHERS stands for the Nationwide House Energy Rating Scheme. It is Australia’s national system for measuring how well a home’s design and construction keep you comfortable without leaning on heating and cooling. Homes are scored out of ten stars, and the score is generated by accredited software that models your actual floor plan, in your actual climate zone, with your actual materials.

A zero star home does essentially nothing to protect you from the weather. Think uninsulated fibro shack: freezing in July, an oven in January. A ten star home holds a comfortable temperature almost entirely on its own. Most Australian housing stock built before energy standards existed sits somewhere depressingly low on that scale, which is why so many of us grew up in houses that required a jumper indoors, and a fan pointed directly at the bed.

What the software actually looks at

A NatHERS assessment is a thermal model, and it is genuinely clever. An accredited assessor feeds in:

– Orientation. Which way your living areas face, and whether your windows are collecting winter sun or coping with summer heat.
– The building envelope. Insulation levels in the roof, walls and floor, and how airtight the construction is.
– Glazing. Window size, placement, frame type and glass performance. Windows are usually the weakest thermal link in a home, so they matter enormously.
– Thermal mass. Materials like concrete slabs and brick that absorb heat and release it slowly, smoothing out temperature swings.
– Shading and ventilation. Eaves, pergolas, external blinds, and whether the design allows cross breezes to do the cooling for free.
– Climate. The same house scores differently in Doonan than it does in Thornbury. NatHERS models against dozens of climate zones, so the rating reflects how the home performs where it actually stands.

The output is a certificate with your star rating, and it becomes part of your building approval documentation.

Why everyone is suddenly saying “seven stars”

For over a decade, the minimum standard for new homes was six stars. The National Construction Code 2022 lifted that minimum from six to seven stars and introduced a second requirement called Whole of Home, and the states have been progressively adopting it. Victoria made it mandatory from May 2024, Queensland followed the same year, and NSW runs an equivalent standard through BASIX.

That one star jump is bigger than it sounds. Moving from six to seven stars is expected to cut heating and cooling energy use in new homes by around 25 per cent. Star ratings are not a linear scale; each additional star gets harder to earn and delivers a meaningful performance improvement.

The Whole of Home rating is the newer half of the equation, and it fills a gap the star rating always had. The star rating assesses the house as a container, how well it holds warmth in winter and resists heat in summer. Whole of Home looks at what runs inside that container: your heating and cooling systems, hot water, lighting, pool pumps. New houses now need seven stars plus a Whole of Home score of at least 60 out of 100. A beautifully insulated shell with a gas hot water unit from 2004 no longer gets a free pass.

Worth knowing if you are planning a build: this framework is staying put. Residential energy requirements in the NCC are paused until mid 2029, so seven stars and Whole of Home are the settled standard for the foreseeable future. No moving goalposts to design around.

Why you should care, beyond the paperwork

Compliance is the least interesting reason to pay attention to any of this. Here is what a good rating actually buys you.

Comfort. This is the one people underestimate until they live it. A well-rated home holds a stable temperature. No more rooms that are unusable for three months of the year, no more racing to shut the house before the afternoon heat arrives. The home does that work quietly, through design.

Running costs. Heating and cooling are typically the largest slice of a household energy bill. A home that barely needs them is cheaper to run every single day, for its entire life. As electricity prices do what electricity prices do, that gap between an efficient home and a leaky one only widens.

Resilience. During a heatwave or a blackout, a high-performing home stays liveable for far longer than a poor one. In a warming climate, that is a genuine safety consideration, particularly for children, older people and anyone unwell.

Resale value. Energy performance is increasingly visible to buyers, and homes that demonstrate it are starting to command a premium. A NatHERS certificate is evidence, in a market otherwise full of vague claims about a house being “nice and cool in summer.”

The bigger picture. Housing is one of the largest levers Australia has on household emissions. Every home designed to need less energy reduces demand on the grid permanently. Good ratings are climate action baked into the building itself, working silently for the next fifty years.

What this means in practice

If you are building or substantially renovating, the single most valuable thing you can do is **engage an energy assessor early**, at concept stage rather than after the drawings are finished. At that point, orientation, window placement and eave depths are still cheap to change. Achieving seven stars through smart design costs very little. Achieving it by bolting expensive glazing onto a poorly oriented plan costs a great deal. The rating rewards thinking, and thinking is free.

If you own an established home, NatHERS assessments for existing dwellings exist too, and they are a useful diagnostic before spending money on upgrades. Often the highest impact improvements are unglamorous: ceiling insulation, sealing gaps, external shading on west facing glass. The star rating framework gives you a way to prioritise rather than guess.

And if you are buying, ask for the rating. New builds will have one. The question itself signals to the market that performance matters, and markets listen when enough people ask.