How to Improve Your NatHERS Star Rating
A homeowner's retrofit guide — exactly which upgrades add stars, what they cost, and the order to do them in
Taylor M
NatHERS & Home Energy Specialist
If your home rated badly, you're not stuck with it
Most existing Australian homes sit between 1.5 and 3 stars — well below the 7-star minimum that applies to new builds under NCC 2022. That's not a verdict on your house. It's a starting point.
With the right sequence of retrofits, almost any home can be lifted by 2–4 stars, and many can be brought up to a 6 or 7-star equivalent. The trick is knowing which upgrades actually move the needle in NatHERS software, and which just feel virtuous.
This guide ranks the upgrades by typical star gain, gives realistic Australian cost ranges, and points you to certified specialists for each one.
Want a quick estimate? Try our free energy rating calculator — it takes under 2 minutes.
Get Your EstimateStep 1 — Get a baseline assessment first
Before spending a cent on insulation or glazing, get a NatHERS Existing Homes assessment. A certified assessor will model your current rating and run "what-if" scenarios — showing exactly how many stars each upgrade would add to your specific home in your climate zone.
Without this, you're guessing. Two homes that look identical from the street can respond very differently to the same upgrade because of orientation, roof colour, existing insulation and glazing.
Step 2 — The upgrades, ranked by star gain
Ceiling & roof insulation
Up to 35% of heating and cooling energy is lost through an uninsulated roof. Topping up batts to R5.0–R6.0 is the single highest-return upgrade in most older homes.
Find an insulation installerDraught sealing & air tightness
Gaps around doors, windows, downlights, exhaust fans and floorboards can equal a permanently open window. Sealing is cheap, fast, and modelled directly in NatHERS software.
Talk to an assessor firstWindow glazing upgrades
Single-glazed aluminium windows are the weakest part of most Australian homes. Double glazing, low-E coatings and thermally broken frames significantly reduce heat loss in winter and gain in summer.
Compare window & glazing specialistsWall insulation
Retrofitting wall insulation is harder than ceilings but delivers strong gains, especially in cooler climates (Melbourne, Hobart, Canberra). Blow-in cellulose or foam can be installed without removing cladding.
Find an insulation installerExternal shading & eaves
Eaves, awnings, pergolas and external blinds on north and west windows block summer sun while still allowing winter sun in. NatHERS rewards correctly sized shading on the right orientations.
Speak to an assessorEfficient HVAC (reverse-cycle)
NatHERS rates the building shell, not appliances — but a high-efficiency reverse-cycle system dramatically reduces the cost of running whatever rating you end up with, and is essential after sealing and insulating.
Find an HVAC installerHeat-pump hot water
Hot water is typically 20–25% of a home's energy bill. Heat-pump systems use roughly a third of the energy of electric resistance and pair perfectly with solar PV.
Find a hot water installerSolar PV (and battery)
Solar doesn't change your star rating, but once you've sealed, insulated and electrified, a 6–10 kW system can offset most of what's left of the bill. Best done last, after the building is efficient.
Find a solar installerReady for an official assessment? Find certified NatHERS assessors in your area.
Find Local AssessorsStep 3 — The right sequence matters
Doing the right upgrades in the wrong order is one of the most common — and most expensive — retrofit mistakes. A good rule of thumb:
- Seal first. Draught-proofing is cheap and makes every other upgrade work harder.
- Insulate the ceiling. Highest star gain per dollar in almost every climate.
- Insulate walls and floor if accessible.
- Upgrade glazing on the worst-performing windows (usually west and large single-glazed panels).
- Add shading to north and west exposures.
- Then upgrade HVAC and hot water — they'll be sized smaller and cheaper to run.
- Finally add solar PV (and battery) to offset whatever load remains.
Steps 1–5 are what move your NatHERS star rating. Steps 6–7 don't change stars but slash your bills once the building shell is doing its job.
What it costs to go from a low rating to 7 stars
| Starting rating | Target rating | Typical retrofit cost | Estimated bill saving |
|---|---|---|---|
| 1.5–2 stars | 5 stars | $15,000 – $35,000 | $1,200 – $2,000 / yr |
| 3 stars | 6 stars | $20,000 – $45,000 | $1,500 – $2,400 / yr |
| 3 stars | 7 stars | $30,000 – $60,000 | $2,000 – $3,000 / yr |
| 5 stars | 7 stars | $10,000 – $25,000 | $700 – $1,200 / yr |
Ranges are indicative, based on a 180–220 m² detached home. Real numbers depend on climate zone, existing fabric and product choices.
Rebates that lower the bill
Most states now offer significant rebates for the same upgrades that improve your NatHERS rating — particularly insulation, hot water, HVAC and solar. The Victorian VEU, NSW Energy Savings Scheme, and federal Small-scale Renewable Energy Scheme can collectively cover 30–60% of common upgrade costs.
See current rebates by stateNot sure where you're starting from?
Use the free calculator for a 2-minute estimate of your current star rating, then connect with an accredited assessor to model upgrade scenarios.
Ready to start improving your home's rating?
Get matched with NatHERS assessors and certified retrofit specialists in your area — insulation, glazing, HVAC, hot water and solar.
Estimate Your Rating
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Explore LocationsReady to get started? Request free quotes from certified assessors.
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