Online Home Value Estimates: What They Miss and How to Use Them

It happens in living rooms every day. A homeowner types an address into a home-value site and a number appears. Sometimes it feels right. Sometimes it feels low, or high. And sometimes it is off by tens of thousands of dollars. Zillow, Realtor.com, Homes.com, Redfin and RPR all use automated valuation models (AVMs). They are useful, but they have limits, and it helps to know what those are before you rely on one.

What the platforms say about accuracy

Zillow publishes its own accuracy figures: a national median error rate of 1.83% for homes on the market and 7.01% for off-market homes, as of 2025 (Zillow). Medians hide a lot of spread. Investopedia, reporting Zillow’s figures, noted that its estimates were off by 5% or more about 16% of the time (Investopedia).

Platforms also disagree with each other. A 2017 Redfin study comparing estimates reported median errors of 2.06% for Redfin, 5.95% for Zillow and 10.26% for Homes.com (Redfin); that is old data from one of the companies being compared, so treat it as a snapshot rather than a ranking. In a 2025 example, one Idaho home showed four estimates across four sites, ranging from about $632,000 to $718,000, a spread of roughly $86,000 (Agents With A Smile). A 2026 podcast on South Louisiana described much larger errors where sales are sparse and parcels are rural (RE: Real Estate Podcast).

Why the models miss

Thin data

AVMs lean heavily on recent comparable sales. When few homes nearby have sold, the model has less to work with, and in shifting markets estimates can lag what agents see in current offers and price changes (Realty Executives).

They cannot see inside

An AVM reads public records, past sales and nearby comparables. It does not walk through the house or judge workmanship. A remodeled kitchen, a new roof or new air-conditioning may never show up in public data, so improved homes can be underestimated and neglected homes overestimated (Realty Executives).

A Chicago brokerage described a large two-bedroom condo that models valued at roughly $575,000 to $600,000. Tax records said “two bedroom,” and the models appear to have assumed a typical two-bedroom size, but the unit had nearly 1,800 square feet, an attached garage with interior access and a 400-square-foot private deck. It was listed at $675,000 and, according to the brokerage, sold above list (MG Group Chicago). One example, not a rule, but it shows how a records error can carry through.

Unusual properties

Custom homes, high-end homes, rural acreage, historic homes and mixed-use properties have fewer true comparables, and estimates for them are less reliable (Realty Executives). The same goes for location-specific features a model may not capture well, such as a water view, a busy road or a lot backing onto a canal.

RPR and confidence scores

RPR, the Realtors Property Resource, offers a valuation model that draws on MLS active, sold and off-market data, and pairs each estimate with a confidence score of zero to five stars reflecting how closely several models agree (RPR). Its estimates are generated through a Realtor rather than shown to consumers directly (Armstrong Field). A 2013 explanation of the score said a five-star score meant a property could be expected to sell within about 10% of the estimate (HAR.com). That guidance is old; check the current definition on the report you are given. A lower score is a cue to look harder at the comparables.

What I suggest instead

• Treat online estimates as a range, not a price. Look at several and note how far apart they are. A wide spread tells you the data is uncertain.
• Ask for a comparative market analysis. A CMA from a licensed agent looks at the actual comparables, condition, upgrades and current competition. It is an opinion of price, not an appraisal, and it should show its work.
• Fix the public record. If your square footage, bedroom count or improvements are wrong in the property appraiser’s records, that error can flow into every AVM. In Palm Beach County you can review your parcel on the Property Appraiser’s site.
• Get an appraisal when the stakes call for it. For estate, divorce or financing decisions, a licensed appraiser’s report is the standard.

The bottom line

Automated estimates are a convenient starting point. They can be high or low, and they are least reliable for homes that are improved, unusual or in areas with few sales. A number on a screen is a starting point, not a pricing strategy. If you would like to talk through how a home in Palm Beach County might be priced, my FAQ explains how I work with sellers.