NatHERS for Existing Homes Is Live: Star Ratings for the House You Already Own

For 30 years, NatHERS star ratings have been something you got for a home you were about to build. That changed this year. Stage 2 of NatHERS for Existing Homes went live on 1 July 2026, opening accreditation to assessors nationally and making an official energy rating available for homes that are already standing. If you own, are renovating, or are about to sell an existing home in NSW, this is worth understanding.

What an existing-home rating is

An accredited assessor inspects and models your home in NatHERS-approved software and issues a Home Energy Rating Certificate with two numbers:

It is the same science used for new-home certificates, adapted for buildings where the plans may be long gone and the insulation has to be verified rather than specified.

Why it matters in NSW

• Renovators get a baseline. Rate the home before you renovate and you can see exactly which upgrades move the number – and design the renovation to capture them. This pairs naturally with the BASIX requirements that already apply to alterations and additions.
• Sellers get evidence. An official certificate turns “we added insulation” into a documented rating. As energy costs stay front of mind, a strong rating is becoming a genuine sales asset.
• Buyers get transparency. A rating on a listing tells you what the running costs and comfort will really be like – before you commit.
• Upgrade programs are aligning. Government efficiency programs increasingly want a consistent way to measure homes before and after upgrades. A national rating scheme is exactly that measuring stick.

Stage 2 specifics

Stage 1 proved the concept with a limited cohort. Stage 2 brings a second-generation assessment tool and method refined from that trial, and opens accreditation and training to all assessors. The focus of the next phase is consistency and scale – better tools, quality assurance and digital workflows so ratings become routine rather than novel.

How this connects to your renovation

If you are planning an alteration or addition in NSW, you already need BASIX compliance for the works. An existing-home rating adds the missing half of the picture: how the whole house performs today, and what the renovation could lift it to. Sequencing matters – a pre-renovation rating, then a design that targets the weak points the model exposes, is the cheapest path to a home that is measurably better, not just newer.

Frequently asked questions

Is an existing-home rating compulsory? No. It is voluntary today. Disclosure requirements have been discussed nationally, but right now this is a tool you choose to use.

Is this the same as a BASIX certificate? No. BASIX applies to proposed building work in NSW. The Home Energy Rating Certificate measures an existing home as it stands. A renovation can involve both.

What does it cost? Pricing is settling as more assessors accredit, and involves a site visit, unlike plans-based new-home work. Contact us and we can point you in the right direction for your situation.

Sources: NatHERS – Existing Homes guidance. Renovating in NSW? Talk to us about the BASIX side of your project.