Zillow Zestimate
Why Your Zillow Zestimate Is Probably Wrong and Why That Matters More Than You Think
If you own a home in Williamson County, there is a near-certain chance you have checked your Zillow Zestimate at some point. Maybe you check it regularly. Maybe you have watched it bounce up and down by $20,000 or $30,000 in a single month without anything changing about your home. Maybe you have used it to form an opinion about whether now is a good time to sell, how much equity you have, or whether a neighbor's home sold for more or less than yours is worth.
I am not here to tell you Zillow is useless. It is not. But I am here to give you an honest picture of what a Zestimate actually is, how significant its margin of error actually is in real dollar terms, and why the number a locally licensed agent produces from a real analysis of your specific home and your specific market is a completely different tool, with a completely different level of accuracy and usefulness.
This distinction matters because the decisions people make based on their Zestimate, whether to sell, whether to refinance, whether a home is priced fairly, are real decisions with real financial consequences. And making them based on a number that could be off by $35,000, $50,000, or more on a typical Williamson County home is a risk worth understanding clearly before you rely on it.
The Numbers: What Zillow's Own Data Actually Shows
According to Zillow's own published accuracy data, the nationwide median error rate for on-market homes is 1.9%, meaning that half of all for-sale homes are within 1.9% of the ultimate sales price, and half are not. For off-market homes, the median error is around 7.0%. That second number is the one that matters most to the typical homeowner, because if you are checking your Zestimate, you are almost certainly not currently listed for sale.
A 7% median error rate sounds like a statistic. Here is what it looks like in actual dollars on homes in the Williamson County price range.
And remember: that is the median error. Zillow reports that 99% of properties have a Zestimate within 20% of the actual value, but even that wide range can lead to costly mistakes. Half of off-market estimates are off by more than 7%. Half are off by less. Some are off by far more. The Blue Ridge Mountains example from a real agent: Zillow had a property estimated at $650,000, and it sold for well over $1.1 million. That is not a rounding error. That is a $450,000 gap.
Why the Zestimate Gets It Wrong: The Reasons Behind the Error
- ▸It cannot walk through your home. The Zestimate works from public records: tax data, square footage, bed and bath count, lot size, and sale history. It cannot see that you renovated the kitchen in 2023, replaced the roof last year, added a pool, finished the garage, or upgraded every fixture throughout the house. If Zillow does not know about those improvements, the Zestimate cannot price them.
- ▸It treats similar homes as identical. A house on a premium cul-de-sac lot with a greenbelt view and a house on the same street backing to a commercial property may have identical square footage and the same number of bedrooms. The Zestimate may value them within a few thousand dollars of each other. A local agent knows the difference is real and prices accordingly.
- ▸It relies on publicly available data, which is often incomplete or outdated. In fast-moving markets like Williamson County, public records can lag by weeks or months. A wave of recent sales that have not yet hit the public record are invisible to the algorithm even though they are shaping the current market.
- ▸It does not understand neighborhood-level nuance. Zillow's algorithm works at scale, across 104 million homes nationally. It cannot meaningfully distinguish between two streets in the same Liberty Hill zip code where homes on one consistently sell for 4% more than the other because of school bus routes, backing conditions, or community access points.
- ▸It shifts toward the list price when a home is listed, making its "accuracy" misleading. When a home goes on the market, the Zestimate often shifts toward the list price. This means the accuracy check is comparing a number that already adjusted to the market, not the number you saw six months ago when you were deciding whether to sell. The improvement in on-market accuracy is partly because the algorithm is simply following the listing price, not independently confirming it.
- ▸It can swing dramatically without explanation. Homeowners in Williamson County regularly see their Zestimate move by $20,000 to $40,000 in a single month with no changes to the home. That volatility is not the market changing. It is the algorithm processing new data inputs and recalibrating, sometimes in ways that have little to do with the actual value of any specific home.
The Part Zillow Does Not Advertise
This is the insight that appraiser Ryan Lundquist has articulated clearly, and it is worth understanding deeply. Zillow measures its own accuracy by comparing the most recent Zestimate before a home sells to the actual sale price. By the time a home is listed and approaching closing, the Zestimate has already shifted toward the list price. So Zillow's accuracy metric is, in a meaningful sense, measuring how well its algorithm tracks a number it can already see, not how well it independently estimates value.
The homeowner checking their Zestimate today, before any decision to list, is looking at the version of the number with the least supporting data, the highest margin of error, and the greatest potential to be off by a meaningful amount. That is not a flaw Zillow hides. It is in their published accuracy disclosures. But it is not the number most homeowners think about when they are looking at the Zestimate as a measure of their home's current worth.
The Zestimate's accuracy depends on location and the availability of data in the area. Markets without widely available market data or limited sales activity might see a more significant margin of error than markets with consistent sales activity and an abundance of market data. In other words, in markets like Liberty Hill where newer developments, custom homes, and acreage properties with limited direct comparables are common, the Zestimate's margin of error is likely to be higher than the published national median, not lower.
Why the Liberty Hill and Williamson County Market Is Particularly Hard for Algorithms
What a Local Agent's CMA Actually Is and Why It Is Different
A Comparative Market Analysis, or CMA, is not the same tool as a Zestimate. It is not an algorithm. It is a professional analysis produced by a licensed agent with direct access to the MLS, current market knowledge, and physical familiarity with your home and your neighborhood. Here is what goes into one.
- ▸A physical walkthrough or detailed assessment of your specific home's condition, finishes, upgrades, and any features that add or detract from value relative to comparables
- ▸Direct MLS access to every closed sale in your neighborhood, including the details behind the numbers: days on market, price reductions, seller concessions, and final sale conditions that public records do not capture
- ▸Careful selection of truly comparable homes, not just homes with similar square footage, but homes with similar lot characteristics, similar finishes, similar positions within the community, and similar buyer appeal
- ▸Adjustments for differences between your home and the comparables: a renovated kitchen adds value, a dated bathroom subtracts it, a premium lot adds a specific dollar amount based on what the market has shown it is actually worth
- ▸Current active listing analysis showing what your competition looks like for the buyer you are trying to attract
- ▸Pending sale data that has not yet closed and does not yet appear in public records, giving you a current picture rather than a trailing one
- ▸Knowledge of community-specific factors: school district changes, MUD district rates, new development impacts, and anything else affecting buyer behavior in your specific neighborhood right now
- ▸A professional judgment call from someone who has sold homes on your street, knows what buyers in your price range are responding to, and can tell you not just what your home is worth but what it will sell for and why
That last point is worth sitting with. A Zestimate tells you what an algorithm estimates your home is worth based on the data it can see. A local agent's CMA tells you what a buyer in today's market is likely to pay for your specific home, based on everything the algorithm cannot see. Those are genuinely different numbers, and in the Liberty Hill and Williamson County market in 2026, the gap between them can be significant in either direction.
The Zestimate is a useful starting point for curiosity. It is not a useful tool for making financial decisions. If you are thinking about selling, refinancing, or simply want to know what your home is actually worth right now, a conversation with a local agent who can produce a real CMA is the answer. And in most cases, it costs you nothing to have that conversation.
The Practical Takeaway for Williamson County Homeowners
Check your Zestimate if you find it interesting. It is a free, accessible way to get a rough sense of the direction the market is moving and how your home fits broadly within it. But do not make any significant financial decision based on it alone. Do not decide whether to sell based on whether the Zestimate meets your expectations. Do not decide whether a neighbor's home was priced fairly based on how it compares to your Zestimate. And do not assume that a Zestimate significantly above or below your expectations reflects what a buyer would actually pay for your home today.
The number that matters is the number a licensed local agent produces from a real analysis of your real home in your real market. That number is based on what buyers are actually paying, for homes that actually compare to yours, in conditions that reflect what is actually happening in the Liberty Hill and Williamson County market right now. It takes maybe 30 minutes of conversation to get that number. It is almost always more useful than anything Zillow can produce, and in this market specifically, the difference can be substantial.
I get asked about Zestimates regularly, sometimes from sellers who are excited because theirs is high, sometimes from sellers who are frustrated because it seems low, and occasionally from buyers who are trying to use it to negotiate. My honest response every time is the same: the Zestimate is a starting point for a conversation, not a conclusion.
When I produce a CMA for a homeowner in Liberty Hill or the surrounding Williamson County communities, I walk through the home, I pull every relevant closed sale from the MLS including the details that public data does not capture, and I give you a number I can defend with specifics. That number may be higher than your Zestimate. It may be lower. In this market, with the level of variation between neighborhoods, lot conditions, and community characteristics, either outcome is possible and neither should be a surprise.
What I can tell you is that in 19 years of working in this market, I have never had a seller regret knowing their home's actual value before deciding whether to list. That knowledge is power, and it is completely free to get. If you want to know what your home is actually worth in today's Williamson County market, reach out. We will have an honest conversation, I will show you the real numbers, and you can decide from there.
Want to know what your home is actually worth right now?
Skip the Zestimate. Get a real CMA from someone who knows this market from the inside. No obligation, no pressure, just an honest number backed by real data.