Why your Rightmove estimate
is probably wrong

You've found a property you like. You scroll down the Rightmove listing and notice a small link: "View estimated value." You click it. A number appears — £425,000, say — and suddenly you feel like you have a grip on things. The asking price is £445,000. That's £20,000 over the estimate. You feel armed.

The problem is that number is probably wrong. Not slightly wrong — potentially wrong by tens of thousands of pounds in either direction. And if you're making an offer based on it, you're negotiating blind.

Here's what Rightmove's estimated value actually is, why it systematically misses what matters most, and how a proper valuation is done.

What is an automated valuation, and how does it work?

Rightmove's estimated value — and those produced by Zoopla, Halifax, and various other portals — are generated by what the industry calls an automated valuation model, or AVM. These are statistical algorithms that estimate a property's value by comparing it to recent sales of nearby properties.

In simple terms: the algorithm looks at what properties in the same postcode (or nearby postcodes) have sold for recently, adjusts for differences in size and property type, and produces a number. It's fast, it's free, and it covers virtually every property in the UK.

It's also based entirely on data that's already publicly available — mainly from HM Land Registry. The algorithm has never been inside your property. It doesn't know if the kitchen was fitted in 2023 or 1987. It doesn't know the lease has 72 years remaining. It doesn't know the boiler failed last winter, or that the loft conversion added 400 square feet of usable space but isn't on the floor plan.

Five things Rightmove's estimate can't see

1. The condition of the property

Two identical terraced houses on the same street can be worth £60,000 apart if one has been renovated and the other has a leaking roof, dated electrics, and hasn't had a coat of paint in fifteen years. An AVM cannot distinguish between them. It may have the Land Registry record showing both sold for similar prices in 2019 — but it has no way of knowing that one has been transformed since then.

This is the single biggest source of AVM inaccuracy. Condition is almost everything in property valuation, and condition is almost entirely invisible to algorithms.

2. The energy performance certificate rating

An energy performance certificate (EPC) rating is increasingly a major valuation factor. A property with an A or B rating will attract a broader pool of buyers — including those using green mortgages with lower rates — than a property with an E or F rating. The latter may also require significant capital expenditure to bring up to future minimum standards.

Research by Halifax found that EPC-A properties sell for up to 14% more than equivalent EPC-D properties. That's £56,000 on a £400,000 house. AVMs don't weight this properly because EPC data, while publicly available, isn't the primary signal in the algorithm — recent sales prices are. And many recent sales were transacted before the market fully priced in energy efficiency.

3. Lease length (for flats)

If you're buying a leasehold flat, the remaining lease length is one of the most important valuation factors there is. Flats with under 80 years remaining are harder to mortgage, harder to sell, and genuinely less valuable. Below 70 years, the value can drop significantly. Below 60 years, some lenders won't touch it at all.

Rightmove's estimate will typically show you the same number whether the lease has 250 years or 65 years remaining. This is a massive blind spot. The difference in value between an 85-year lease and a 65-year lease on an equivalent flat in the same building can easily be £20,000 to £40,000.

4. Market position and time on market

AVMs are backward-looking. They're based on what similar properties sold for, not what they're currently trading at. In a fast-moving market — or a fast-declining one — this lag can be significant. In January 2023, when interest rates were rising sharply, AVM estimates were still reflecting 2022 sale prices. Buyers who relied on them were consistently overpaying relative to where the market had actually moved.

More practically: a property that's been on the market for four months has a very different implied value than one that's been listed for four days. The AVM doesn't know this. A motivated seller with a property stuck at an aspirational price is a very different negotiating situation from a fresh listing at a realistic one.

5. Local micro-factors and property-specific issues

Is the property directly under a Heathrow flight path? Is there a planning application for a 200-home development on the field behind it? Is the road it's on classified as a flood risk zone? Are there Japanese knotweed remediation costs lurking in the garden survey?

None of these are in an AVM. They're either not digitised at all, not in the data the algorithm ingests, or too localised to affect the comparable sales pool it draws on. Yet any one of them could legitimately knock 5–20% off the market value of a property.

So how does a professional actually value a property?

When a chartered surveyor — or an experienced buying agent — values a property, they don't press a button. They work through a series of adjustments, each one bringing the estimate closer to reality. Here's what that looks like in practice.

That's the difference between an AVM and an actual valuation. The AVM produces a number. The waterfall analysis produces an argument — a reasoned, data-backed case for why a property is worth what it is, and why it isn't worth more.

Why does this matter for your offer?

It matters because the person sitting across the negotiating table from you — the estate agent, acting for the seller — almost certainly has a more sophisticated view of value than "the Rightmove estimate said X." They know how long the property has been on the market. They know what offers have already been turned down. They have a sense of how many active buyers are interested.

If you walk into that negotiation armed only with a Rightmove estimate, you're bringing a number to a conversation that deserves an argument.

The buyers who consistently get better deals are the ones who can say, with evidence: "The comparable sales on this street suggest a value of £385,000 to £400,000. The EPC rating is below average for the area. The property has been on the market for 11 weeks. My offer reflects that." That's a hard argument for an agent to dismiss.

What AVMs are actually useful for

To be fair, automated valuations aren't worthless. They're genuinely useful for:

• Initial triage — quickly screening whether a property is in the right ballpark before you invest time in a viewing
• Tracking a street or area over time — relative changes in AVM estimates can indicate market direction, even if the absolute numbers are off
• Mortgage broker or lender context — lenders use their own AVMs as a first pass, and understanding roughly what yours might say is useful

What they're not useful for is deciding what to offer on a specific property you're serious about buying. For that, you need a proper comparable analysis, with adjustments for the specific characteristics of the property you're looking at.

The bottom line

The Rightmove estimate is a useful starting point and a terrible finishing point. It tells you approximately what properties in the area have been selling for. It tells you nothing about whether this specific property, at this specific point in time, with its specific condition, EPC rating, lease terms, and market history, is worth the asking price.

The gap between "area average" and "this property's actual market value" is where buyers lose — or save — significant sums of money.

Rightmove's estimate gives you a number. What you need going into a negotiation is an argument. Those are very different things.