Home energy efficiency scores explained: what your score means and what it doesn't

Last updated: April 2026

What an energy efficiency score is

A home energy efficiency score is a numerical rating from 0 to 10 that estimates how energy-efficient your home is compared to others. It's standardized so you can compare homes directly — similar to how a fuel-efficiency rating works for cars.

The score is based on a modelled estimate of how much energy your home would use to maintain comfortable temperatures, not on your actual energy bills. Your real bills depend on how you use the home, what temperature you set your thermostat to, and your electricity tariff — factors the score deliberately doesn't include.

Score scale (0–10): The higher your score, the more energy-efficient your home's building envelope and systems are estimated to be. The specific factors that determine your score include your home's insulation, heating and cooling systems, hot water systems, windows, draught sealing, construction age, roof colour, and climate zone.

How the score is calculated

The HEA Energy Score uses a custom model developed by VALAI to estimate your home's energy efficiency.

The score is based on available data about your home, its location, and features that may affect energy use, comfort and efficiency. This includes property details, climate conditions, and whether your home may have features such as solar panels, insulation, or heating and cooling systems.

The model creates a standardised estimate so homes can be compared fairly. This means the same home should receive the same score regardless of who assesses it, because the calculation method is consistent.

Important: The score is a modelled estimate, not a physical inspection. It predicts energy use based on building characteristics, not on measured data from your home.

What your score means in practice

A score reflects your home's building envelope and systems, not your energy behaviour or tariff.

Example: Two homes with the same score of 5

Both homes have:

• Similar insulation levels

• Similar HVAC systems

• Similar age and construction

But their actual energy bills might differ because:

• Home A: Family of 5, keeps heating at 22°C, electricity tariff $0.38/kWh → bill $3,200/year

• Home B: Couple, keeps heating at 20°C, electricity tariff $0.32/kWh → bill $2,100/year

The score (5) is the same. The actual bills are different.

What the score does NOT do

Important limitations to understand:

It does not predict your energy bill

The score estimates energy use in a model, not measured from your home. To predict your actual bill, you'd need:

• Your specific electricity and gas tariffs

• Your household size and preferences

• Your actual thermostat settings

It does not account for solar or batteries

The score rates your home's building envelope and systems only. Solar generation and battery storage are benefits on top, not included in the score.

It does not predict payback periods for upgrades

The roadmap page shows that insulation typically pays back in 3–5 years and heat pumps in 4–6 years, but your payback depends on:

• Your current electricity tariff

• Your current heating/cooling system

• Your climate zone

• Available rebates in your state

It does not replace a professional energy audit

The score is a quick assessment tool. A professional energy assessor (accredited under NatHERS or the Residential Efficiency Scorecard) can:

• Measure air leakage

• Identify specific thermal bridges

• Model star ratings for mortgage/loan purposes

• Provide tailored upgrade recommendations

It does not measure actual energy consumption

It estimates energy needed to maintain comfort, based on average assumptions. Your real consumption depends entirely on how you use the home.

How it compares to other ratings

Energy Score (HEA model)

• Scale: 0–10

• Calculation: Custom VALAI model, ~50 building characteristics

• Purpose: Quick baseline assessment, comparing homes

• Cost: Free (online tool)

• Time: ~10 minutes online

NatHERS Star Rating (0–10 stars)

• Scale: 0–10 stars

• Calculation: Standardised software model, specific Australian homes

• Purpose: Building code compliance, mortgage/loan qualification

• Cost: $300–600 for professional assessment

• Time: ~1 hour site visit + assessment

• Note: Used by banks and for new construction

Residential Efficiency Scorecard

• Scale: Detailed report with recommendations

• Calculation: Government-accredited assessor visits home

• Purpose: Detailed audit, access to specific rebates

• Cost: $200–400

• Time: 1–2 hours on-site

• Note: Professional, measured (not modelled)

Improving your score (and actually saving money)

Your score improves when you upgrade your home's building envelope and systems. But not all upgrades are equally cost-effective.

The best sequence is:

1. Insulation (envelope) — improves comfort + reduces heating/cooling load

2. Heating/cooling systems (heat pumps, efficient gas) — replaces inefficient baseline

3. Hot water — typically 25% of household energy use

4. Appliances — replace old refrigerators, washers, etc.

5. Solar — generates own energy (but only after envelope is sealed)

For detailed payback data and a worked example, see the whole-of-home energy upgrade roadmap.

To understand insulation priorities by climate zone, see insulation R-values explained.

For heat pump options and costs, see heat pumps for Australian homes.

When to get a professional assessment

Get your score assessed online (HEA tool) when:

• You want a quick, free baseline of your home's efficiency

• You're curious how your home compares to others

• You want general upgrade suggestions

Get a professional NatHERS assessment when:

• You're buying or selling a home (lenders often require it)

• You want a star rating for your mortgage application

• You're building new and need code compliance verification

Get a professional energy audit (Residential Efficiency Scorecard) when:

• You're planning major upgrades and want tailored recommendations

• You want access to specific government rebate programs

• You need measured data (not modelled) about your home's performance

• You want to understand air leakage and thermal bridges in detail

What to read next

• Whole-of-home energy upgrade roadmap — prioritised sequence of upgrades with payback data

• Heat pumps for Australian homes — types, costs, and payback periods

• Insulation R-values explained — what insulation you need by climate zone

Sources

• HEA Energy Score Methodology (VALAI custom model)

• NatHERS documentation (Australian Government)

• Residential Efficiency Scorecard (Government-accredited assessment)