Are Zillow’s Zestimates Accurate?

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|10 min read

There’s an innate curiosity that comes with seeing an estimated dollar value attached to our biggest asset. But for those truly looking to understand their home’s market worth, the pressing question becomes: is a Zestimate accurate?

We’ve all checked our Zestimate at one point or another or investigated the home values in our neighborhood. As the go-to tool for gaining insight into potential property values, Zillow’s Zestimates have become one of the most relied-upon resources for homeowners and real estate investors.

While not a replacement for an appraisal, the Zestimate can offer homeowners and investors a helpful starting point when gauging a property’s worth.  But with only an algorithm and impersonal data points to rely on, how close do these calculated figures land to a property’s true worth?

Let’s look honestly into how Zillow arrives at its famous Zestimates and clarify what kind of accuracy homeowners can expect from this calculation. Understanding the capabilities and limitations of the Zestimate tool enables homeowners to determine better when—and when not—to rely on this digital assessment of their home’s market value.

How Zestimates Work?

Zillow’s AI home value estimator provides property owners and home shoppers with an automated valuation — the Zestimate.

This estimated valuation aims to give users insight into a home’s likely market value. But how does Zillow arrive at each Zestimate figure?

To calculate a Zestimate, Zillow utilizes an advanced artificial intelligence called a neural network. Neural networks are systems inspired by the human brain that can process enormous amounts of data and recognize complex patterns.

The Zestimate neural network analyzes hundreds of millions of data points from various sources to determine a home’s value. The Zestimate relies on analyzing various data inputs through Zillow’s proprietary algorithmic model; these include:

  • Property details like square footage, location, and number of bathrooms/bedrooms.
  • Information from active listings (on-market data), including asking price, description, similar homes recently sold nearby, and how long other comparable properties have been on the market.
  • Off-market listings and records, such as tax assessments and prior transaction prices,.
  • Market trends in the overall real estate market, including seasonal fluctuations in buyer demand.

By mapping the connections between all these inputs, the AI system has learned how attributes and current housing trends correlate with market values. Through years of learning and an incredible amount of data, it has become the tool that can generate a Zestimate based on the patterns identified.

Ultimately, Zestimates are the result of a sophisticated algorithm that distills massive amounts of information to generate automated property valuations at scale.

Zestimates are refreshed weekly as new inputs emerge. While Zestimates don’t have a guaranteed accuracy, Zillow benchmarks and aims for median errors below a certain percentage when comparing against final sale prices.

Naturally, areas with richer data availability tend to yield more precise Zestimates. By maintaining up-to-date home facts, owners can help optimize their Zestimate over time.

While not a replacement for professional appraisals, the Zestimate gives users initial property valuation insight into the current real estate market.

How Accurate is Zestimate?

A Zestimate valuation can be highly accurate under ideal conditions, such as when estimating a home that has recently sold or in an area in which a lot of data is available.

The accuracy of a Zestimate depends entirely on the quality of the underlying data used. Estimates that are backed by a lot of data are likely more accurate. This means Zestimates are more reliable in areas with a lot of transaction data and on properties with clear ownership histories and fully detailed profiles with updated photos and property details.

On the other hand, in areas where there isn’t much information, such as new developments or rural neighborhoods, Zestimates are less reliable. This is because there aren’t enough comparables or data for Zestimate’s algorithm to learn from.

Zillow conducts ongoing studies to evaluate the accuracy of its Zestimates. If you ask Zillow, the Zestimate you see on your house or any house you are looking at is very accurate. They have a self-published nationwide median error rate of 2.4% for on-market properties and a 7.49% median error rate for off-market properties.

That median percentage just looks at the whole country. However, some individual states have even less accurate estimates. Some of the most reliable metropolitan areas include Colorado Springs (CO), Fort Collins (CO), and Phoenix (AZ), where there are high volumes of transactions. However, there are regions, such as Vermont, which have very poor accuracy.

While Zillow claims its estimation methodology improves over time as it incorporates more sales data, a single Zestimate still cannot substitute a professional appraisal. Home sellers should be aware of the limitations in automated valuation systems and treat any

Zestimate is simply an initial indicator of price, not a guarantee. Even Zillow’s own co-founder Spencer Rascoff sold his home for way less than the projected value – it ended up going for 40% below the Zestimate.

Your best resource for understanding your home’s market value is an on-site evaluation by a local real estate professional who can provide a more reliable market value. Use FastExpert to connect with a top real estate agent in your area who can provide you with a value estimate.

Understanding Accuracy of On-Market Zestimates

Zillow is generally more accurate when estimating the value of homes that are currently for sale on the market. This is because up-to-date listing information gives the Zestimate algorithm more current data to work with.

For on-market homes, Zillow has access to the listing price, fresh interior and exterior photos, and detailed descriptions of features and updates. This information provides the model with richer, real-time facts about the property versus relying more on past records.

Additional data like the number of days a house has been on the market and any price reductions also helps Zillow adjust its estimated value closer to what a home may realistically end up selling for. This evolving data stream allows Zestimate to self-correct and even helps the algorithm improve Zestimates on off-market properties.

Zestimates for properties that are off-market involve estimating value based on older data. The model must rely more on past sales of comparable homes rather than the most up-to-date insights that multiple listing information provides for on-market properties.

Let’s look at an example of how Zestimate’s nationwide median error rate applies to real-life values. Using an active listing with a $800,000 Zesimate, the 2.4% error rate equates to a margin of about $19,200, meaning it could sell between $780,800 to $819,200. This is a difference of over $38,000. This variance is not inconsequential and needs to be understood when relying on Zestimate data.

Understanding the Accuracy of Off-Market Zestimates

Zestimates of off-market properties tend to be less reliable than active listings, with a 7.49% national median error rate. Why? For off-market homes, Zillow’s valuation model relies more on older records rather than fresh listing details.

Using the $800,000 house example, a 7.49% error rate corresponds to a margin of about $59,920 – resulting in a value range from $740,080 to $859,920. That’s a property valuation difference of over $119,000.

The accuracy of Zestimates is a problem for homeowners, but even more so for investors who rely on this data. For real estate investors analyzing properties, variance could significantly impact financial projections like anticipated monthly cash flow, capitalization rate, and overall investment viability.

Homeowners who rely on Zestimates when estimating their equity also need to be careful. It’s easy for owners to think their home is worth more than it is. The best source of property is a professional valuation or estimate from a real estate agent. Zestimates should only be used as a guide.

Is Zillow’s Zestimate Trustworthy?

Deciding if Zillow’s Zestimate is trustworthy depends on the use you are relying on it for. If you want to get a general idea of an off-market home’s market value, then it can be a good guide.

However, it shouldn’t be relied on when making an investment decision or when deciding how much to offer on a home.

Zestimates are only as trustworthy as the data provided and the consistency of market conditions. If a market is rapidly declining or appreciating, don’t expect Zillow’s Zestimate to be realistic.

Zillow Does Not Replace a Professional Appraisal

No computer algorithm can replace a real estate professional’s expert eye and in-person presence when properly assessing a home’s worth. A service like Zillow is only as good as the info it has access to input into its system. But an appraiser will actually visit and tour the property inside and out, then compare size, features, and finishes to other properties to provide a valuation.

Home improvements like upgraded fixtures, recent repairs, and floor plans are all data an algorithm has limited capacity to account for. An appraiser trained in the local market understands trends that affect prices and can see details that aren’t available online.

While an appraiser can factor in property features, they also understand the subjective human element. This could include the flow of the home, sounds from outside, style decisions, and more that could impact how much a buyer is willing to pay.

When major financial decisions are at stake – like selling a home or taking out a loan, you want reliable information on how much a property is worth. A quick online estimate doesn’t cut it compared to an in-home professional appraisal.

Zillow estimates are fine for a very general overview, but if you need real data on your home’s valuation, don’t gamble; instead, engage a professional appraiser or real estate agent who can give you the most accurate estimate.

Will My Home Sell for the Zestimate?

It’s important to remember that a Zestimate or even a professional appraisal is simply an estimate of a home’s market value based on current data and conditions. There is no guarantee that a home will end up selling for an estimated price. A property’s realized selling price could easily be higher or lower than its Zestimate.

The ultimate selling price of a home depends on a variety of market factors. Inventory levels, buyer demand, median prices, competing listings, interest rates, and overall economic conditions influence buyers’ willingness to pay. No estimate can perfectly predict supply and demand considerations or fully understand buyer perception.

A hot housing market with multiple buyers may drive bids well over the Zestimate. Alternatively, an oversupply of properties and a lack of buyers could mean realizing less than estimated. These market shifts are outside the control of homeowners, valuers, or estimating algorithms and models. The only way to know exactly what a property will sell for is to list it on the market and start receiving offers.

Limitations of Zestimates

While online estimation tools give homeowners a general sense of their property’s value, there are some important limitations to remember.

Firstly, Zestimates are not a substitute for appraisal. Online estimates are algorithm-generated values based on available data, not certified appraisals. Algorithms can’t account for all property details or do an in-person evaluation like a licensed appraiser, so estimates may differ significantly from an official appraised value.

Subjective attributes are challenging to model. Intangible value drivers like natural light, aesthetic charm, or curb appeal are difficult for any algorithm to quantify, but they profoundly shape buyers’ desires. Estimates won’t capture these intangible influences on worth in the same personalized way an experienced agent can.

Secondly, it’s common for the data that Zillow relies on to be outdated, and it may not reflect recent upgrades. If renovations, additions, or even damages aren’t documented in public records used by algorithms, estimates won’t incorporate these value-impacting changes.

For example, Zillow might know that a new kitchen was installed based on approved permits, but it doesn’t know the quality of finishes or kitchen design unless new photos are uploaded. Significant differences between actual property attributes result in inaccurate estimates.

Lastly, Zestimates and professional valuations struggle to keep pace with market conditions. This is especially apparent in in rapidly appreciating or declining markets, when the comparable sales data relied on becomes outdated quickly.

Zestimate’s biggest limitation is that its accuracy is directly tied to data availability. Regions with fewer recent transactions or new developments with limited comparable properties to benchmark against increased inaccurate Zestimates. With fewer local housing market data to reference, prediction accuracy drops compared to busier markets with ample sales to analyze.

While Zestimates is a convenient starting point, homeowners should utilize estimate tools judiciously and supplement them with additional market research and professional appraisals when important financial decisions depend upon an accurate property valuation.

Are There Alternatives to Zestimate?

While Zillow’s Zestimate is one of the most well-known online home valuation tools, there are several other options that real estate professionals and homeowners frequently use.

Professional Appraisals

Professional appraisals are considered the most official home valuation option. They are essential for important financial decisions that rely on an accurate estimate of property valuation, like obtaining a mortgage or refinance. A professional appraisal provides an authoritative market value determined by a licensed appraiser performing an in-person inspection and comparative analysis review.

Appraisals consider recent sale prices of similar homes to understand how exterior/interior traits and market conditions affect a given property’s worth. This vetted process still represents the traditional “gold standard” for buyers, sellers, and lenders seeking a verified value.

Real Estate Agent Valuations

While online estimators offer convenience, real estate agents provide localized expertise valuable for pricing strategies or general value knowledge. With market-specific knowledge and access to comprehensive Multiple Listing Services (MLS) databases, agents factor insights often unavailable through algorithms. A professional real estate agent will often visit a property in person and conduct a thorough walkthrough before providing their price estimate.

Getting a valuation from a real estate agent is a great start if you are considering selling or refinancing your home. An agent’s professional guidance incorporates community familiarity and updated data that algorithms lack.

FastExpert can help you connect with an experienced local real estate agent who will provide you with a comparative market analysis of your home’s value.

Other Online Estimation Tools

In addition to Zillow’s widely known Zestimate, several other online valuation resources give homeowners a sense of their property’s potential worth. While no algorithm replaces an in-person appraisal, these free tools offer ballpark figures using available data points.

Redfin

Redfin taps into MLS data sources with direct integration of additional data, as the company is also a brokerage. This allows their algorithm to consider fresh data that other sites lack. The Redfin Estimate is considered highly accurate, with median errors just over 2% for properties on the market.

Realtor.com Valuation

Realtor.com’s RealEstimate analyses homes using estimates from three respected independent valuation partners – Collateral Analytics, CoreLogic, and Quantarium. Viewing estimates from multiple underwriting-grade sources gives homeowners a more holistic view of potential worth.

Real estimates are refreshed each time the property or market changes, keeping it updated. While algorithm-based, Realtor.com’s approach leverages expertise from leading analytics firms trusted across the real estate industry. While it does offer a fuller sense of a home’s value, it does not replace speaking with a local real estate agent.

Chase Home Value Estimator

Using homeowners’ user-submitted data and nearby comparable properties, Chase provides a general preliminary value. Their tool aims to give owners insight rather than replace professional evaluations. It’s another great tool that delivers an estimated value that can be compared against other AI-generated values.

Bank of America Home Value Estimator

Like Chase, Bank of America requests property specifics from the owner and then benchmarks against comparable properties. While convenient for quick guidance, a licensed expert remains best to determine an authoritative market price.

No tool perfectly anticipates the personalization or accurate estimate that an in-person agent brings. But checking multiple online valuations against an on-site appraisal helps individuals gauge what their property might fetch in today’s market conditions.

Get a Full Picture of Your Home’s Value

As the most well-known source for preliminary home valuations, Zestimates provide a useful starting point for understanding a property’s worth. However, it’s important for homeowners and buyers to understand the limitations of these automated estimates compared to professional appraisals and agent valuations.

The precision of any Zestimate relies entirely on the quality and completeness of underlying data inputs. Areas with sparser real estate records or more unique household characteristics yield less reliable figures.

Zillow’s reports of median error rates nationwide help provide perspective on typical accuracy. But individual estimates may vary significantly from this average, especially for unlisted homes.

While a convenient online resource, Zestimates was never meant to replace the expertise of human professionals. An on-site evaluation by a local real estate agent or a certified appraisal evaluates valuable subjective factors no automated system can match.

If you want a comprehensive valuation of your property, work with a trustworthy local real estate agent. They are in tune with changing market conditions, understand buyer preferences, and will perform an in-person inspection to best understand your home’s features. Real estate agents provide a detailed comparative market analysis and personalized guidance that Zestimates cannot.

Find a top-rated real estate agent with FastExpert. Explore their track record, read reviews, and find the right professional for you.  

Kelsey Heath

Kelsey Heath is a real estate content specialist with an extensive background in residential, industrial, and commercial property. She has been involved in the industry for a decade as a professional and personal investor, gaining a deep understanding of the market and trends. With a passion for written communication, Kelsey loves helping people understand the sometimes-complicated concepts behind real estate and is now a sought-out guest and ghostwriter.

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