Property value estimates compared: why realestate.com.au, Domain and the banks disagree

Why the numbers differ

Every online estimate comes from an automated valuation model. Each site builds its own model, feeds it its own data, and updates it on its own schedule. So when your home is easy to value, with plenty of similar recent sales nearby, the estimates tend to land close together. When it is harder to value, they spread apart. The gap between them is useful information in its own right.

Where the main estimates come from

• realestate.com.au shows a "realEstimate" powered by PropTrack, part of the REA Group, which also runs property.com.au.
• Domain shows estimates on its property profile pages, drawn from its own data and models.
• OnTheHouse is owned by CoreLogic, one of the largest property data providers in Australia.
• Bank and lender tools such as CommBank, ANZ, NAB and Lendi offer property reports and estimates, generally built on data from specialist property data providers.
• Newer sites such as view.com.au and a growing number of AI valuation tools add their own models to the mix.

Different owners, different data and different methods mean different numbers. None of them has seen inside your home.

Five reasons the numbers disagree

1. Different data. Each provider holds slightly different records of sales, listings and property features.
2. Different property details. One site may think your home has three bedrooms, another four. Out-of-date details are one of the most common causes of odd estimates.
3. Different comparable sales. Each model chooses which nearby sales matter, and how much weight to give them.
4. Different update timing. A recent sale next door may be in one model and not yet in another.
5. Different treatment of unusual homes. Views, heritage character, steep blocks and one-off designs are handled differently by each model, and often poorly by all of them.

Which estimate should you trust?

There is no single most accurate site for every home. Instead of picking one, read them together:

• Check the confidence rating and range width. A narrow range with high confidence is worth more than a precise-looking figure with low confidence.
• Check the property details each site holds. If a site has your bedrooms, bathrooms or land size wrong, discount its estimate. Some portals let owners update these details.
• Look at the spread. If the estimates are close, your home is probably typical for the area. If they are far apart, the data is struggling, and local knowledge matters more.
• Test them against real sales. Find three to six recent sales of similar homes nearby. Whichever estimate sits closest to that evidence is the one to lean on.

A note for the Blue Mountains and regional NSW

Estimates spread furthest where homes vary a lot and fewer similar sales happen, which describes much of the mountains and the Lithgow area. We explain why in are online property value estimates accurate?, and our suburb guides cover what drives value in each area.

Turning three estimates into one number you can trust

1. Note each site's estimate, range and confidence.
2. Discard any based on wrong property details.
3. Build your own range from recent comparable sales, using six free ways to check property value.
4. Adjust for what the models cannot see: renovations, condition, views and layout.
5. Get a local opinion to confirm where your home sits in the range.

For more on how the models work, and their blind spots, read are online property value estimates accurate?