How Accurate Are Online House Valuations?

An online house valuation is an estimate produced by an automated model, not a valuation of your particular home. It works from records — past sold prices, property attributes and local market movement — and it has never seen inside the house. That makes it a reasonable orientation point for an ordinary, unmodified home in an area with plenty of recent sales, and much less reliable for anything unusual. Nobody, including the people who build these models, can promise how close the figure will be for your specific property.

How does an online house valuation work?

Online valuation tools use an automated valuation model. It compares the property's recorded attributes with recent sales of similar homes nearby and adjusts for how the local market has moved since.

The inputs are typically:

• Sold prices of comparable properties nearby, drawn from published land registry data.
• The property's own last sold price and date, where one exists.
• Recorded attributes: property type, tenure, number of bedrooms, and sometimes floor area from an Energy Performance Certificate.
• Local market movement, often derived from the UK House Price Index.
• Anything the homeowner types in, on tools that ask you to confirm details.

Everything in that list is a record. None of it is an observation of the actual house on the day you ask.

So how accurate are they?

Accuracy varies by property and by area, and no honest general figure exists. Estimates are closest for standard homes in dense areas with many recent comparable sales, and least reliable where evidence is thin or the property is unusual.

Providers do not consistently publish accuracy statistics, and where they do the figures are not comparable between tools. Rather than trusting a headline accuracy claim, judge the conditions:

• Likely to be closer: a 1930s semi on a street of near-identical 1930s semis, several sold in the last year, no extensions.
• Likely to be further off: a converted barn, a listed cottage, a flat in a block with an unusual lease, or a house extended twice since it last sold.
• Unreliable: a new-build with no sale history in a development that has only just completed.
• Unreliable: any property in an area where almost nothing has sold recently.

A useful test is to look at the comparable sales yourself. If you can find several genuinely similar homes sold nearby in the last year, the model probably had good evidence too. If you cannot, neither could it.

What can an online valuation not see?

Condition, quality of finish, layout, outlook, noise, damp, structural problems, recent renovations and the details of a lease are all outside the model's view.

• Whether the kitchen and bathroom were replaced last year or in 1998.
• Whether the roof leaks or there is subsidence.
• Whether the garden faces south or the windows face a main road.
• Whether the loft conversion was done properly and with building regulations approval.
• How many years remain on a lease, and what the service charge and ground rent are.
• Whether the local market has turned since the last comparable sale completed.

These are precisely the factors that make two record-identical homes sell for very different prices — which is why an inspected valuation exists at all.

Why do different websites give different valuations?

Each tool runs a different model on a slightly different dataset, refreshed on its own schedule. Different assumptions produce different figures for the same house.

There is no single official valuation for a property, so disagreement between tools is expected rather than evidence that one is broken. Where estimates differ widely, treat the spread as a signal: it usually means the underlying evidence is thin, and the honest answer is a range rather than a number.

When is an online valuation useful?

Use it for orientation — early curiosity, a rough equity check, or a sanity test before speaking to agents. Do not use it as the basis for a decision that involves money changing hands.

• Useful: getting a rough sense of a home's value before you start researching properly.
• Useful: checking whether an asking price is broadly in the right region.
• Useful: tracking a rough direction of travel over time.
• Not sufficient: setting an asking price, making an offer, or negotiating.
• Not sufficient: probate, divorce, tax or any figure that must be defensible — that needs a RICS valuation.

What is more reliable than an online estimate?

Comparable sold prices you have read yourself, two or three estate agent appraisals, and — where it matters — a valuation from a RICS-registered valuer who has inspected the property.

Start with the evidence. Sold prices for England and Wales are free to search at the HM Land Registry Price Paid Data search, and our guide to what houses on your street have sold for explains how to compare them properly. Then get local agents in, and if the figure has to carry formal weight, commission an independent valuation through the Royal Institution of Chartered Surveyors.

For the full set of options, see how much is my house worth.

What PicAHome does instead

PicAHome does not produce an estimated valuation. It shows you the real transactions and property details behind a home: what it last sold for, its earlier sales, key details about the property and what is happening nearby. We would rather give you the evidence and let you form a view than hand you a confident-looking number a model invented.