Why Your Home’s Zestimate May Be Wrong!
If you’ve ever wondered what your home is worth, chances are you’ve looked it up on Zillow. In seconds, you can enter an address and receive a Zestimate—a computer-generated estimate of what Zillow believes your home may be worth.
It’s convenient. It’s easy to understand. And it can be a useful starting point.
But if you’re thinking about selling your home, buying a property, refinancing, or making an investment decision, there’s an important distinction to understand: a Zestimate is not an appraisal, and it may not accurately reflect what your home would actually sell for in today’s market.
Zillow itself makes this distinction. The company describes the Zestimate as an estimate of market value and states that it should not be used as a substitute for an appraisal.
How Does a Zestimate Work?
The Zestimate is generated using a proprietary valuation model that analyzes hundreds of data points. These can include public records, tax assessor information, MLS data, previous sales, square footage, bedroom and bathroom counts, location, listing information and broader market trends.
That sounds remarkably comprehensive—and it is.
The problem is that real estate valuation isn't simply a matter of plugging property characteristics into a formula.
Two homes with the same number of bedrooms, bathrooms and square footage can have dramatically different market values.
This is particularly true in Sonoma County real estate, where location, lot size, views, condition, construction quality, privacy, outbuildings, pools, vineyards, ADUs and even the character of a particular road or neighborhood can have a significant impact on what buyers are willing to pay.
The Problem With "Average"
Automated valuation models work best when there is a large amount of consistent, reliable data.
That can be particularly challenging in Sonoma County.
Consider two homes in Sebastopol. One might be a relatively straightforward 1,800-square-foot home on a typical residential lot. Another might have the same 1,800 square feet but sit on five acres, include an ADU, have a pool, extensive landscaping and views of the surrounding countryside.
A computer model may recognize some of these characteristics, but it doesn't necessarily understand how buyers in that particular market segment value them relative to one another.
The same issue exists throughout Sonoma County. A property in Sebastopol, Healdsburg, Santa Rosa, Petaluma, Guerneville or West Sonoma County can have very different market characteristics even when the homes appear similar on paper.
And in smaller or more specialized markets, there may simply not be enough truly comparable sales for an automated model to make a highly precise prediction.
The Data May Not Tell the Whole Story
Another important consideration is the accuracy and completeness of the underlying property data.
Zillow acknowledges that incomplete or incorrect information can affect a Zestimate. The company recommends that homeowners review and update their property facts because unreported additions, remodels and other improvements may not be reflected in the valuation.
This can be a significant issue:
Was the kitchen completely remodeled?
Was an additional bathroom added?
Is there a permitted ADU?
Was the home substantially renovated?
Does the property have owned solar?
Is there a pool?
Does it have a detached workshop or barn?
Is the home actually a three-bedroom property, or does the county record still show two bedrooms?
These details can matter considerably when determining market value.
Condition Is One of the Biggest Variables
One of the most difficult things for any automated valuation model to fully capture is condition.
A 2,000-square-foot house that has been completely remodeled with high-quality materials is not necessarily worth the same as another 2,000-square-foot house that has dated finishes, deferred maintenance and an aging roof.
This is where direct market analysis becomes particularly important.
When determining a property's market value, we look at the condition and quality of the subject and compare it with the condition and quality of actual comparable sales.
The question isn't simply, "What do similar-sized houses sell for?"
The more important question is:
"What did buyers actually pay for properties that were similar to this property in the characteristics that matter?"
Location Can Be More Complicated Than a ZIP Code
An automated model may understand that two properties are located within the same ZIP code.
A local real estate professional understands that they may not compete for the same buyers.
In Sonoma County, a few blocks can make a meaningful difference.
A property may be located near a busy roadway, have a superior view, sit in a more established neighborhood, have better access, or be located on a particularly desirable street. Conversely, a property may have characteristics that aren't immediately apparent from public records.
This is particularly relevant in areas such as West County and Sebastopol, where properties can transition quickly from conventional suburban neighborhoods to semi-rural properties with acreage.
The physical characteristics of the property and the behavior of local buyers matter.
Zillow's Own Numbers Tell an Important Story
It's also important to be fair to Zillow. The Zestimate has become considerably more sophisticated over the years, and Zillow continues to improve its valuation models using machine learning and large amounts of housing data.
But even Zillow acknowledges that accuracy varies depending on location and the availability of data.
According to Zillow's current published statistics, the national median error rate is approximately 1.83% for on-market homes and 7.01% for off-market homes. That means that while the model can be quite accurate overall, there is still meaningful potential for error—particularly for homes that aren't currently listed for sale.
And remember: a median error is not the same thing as saying every Zestimate is within that percentage. Half of the estimates are closer than the median error and half are farther away.
For a $1 million property, a 7% difference represents $70,000.
For a $1.5 million property, it's $105,000.
That's not necessarily a small difference when you're deciding how to price a home.
So What Is Your Home Really Worth?
The answer is ultimately determined by the market.
A Zestimate can provide a useful data point. So can an automated valuation from another website. But neither should be considered the final word when you're making an important financial decision.
A more comprehensive valuation looks at recent comparable sales, current competition, market conditions, property characteristics, condition, quality, location and the specific features that differentiate one property from another.
That's where local expertise becomes important.
That’s why we approach property valuation from a somewhat different perspective. Our experience isn't limited to selling real estate. We also bring an appraisal background and an understanding of how properties are analyzed for market value.
That means we're not simply asking, "What does the algorithm say?"
We're asking:
What are buyers actually paying for properties like yours—and why?
That distinction can make a significant difference when you're preparing to sell a home, evaluating an investment, or deciding whether a property is worth pursuing.
Don't Let a Zestimate Set Your Price
If your Zestimate is higher than you expected, it can be tempting to assume you've discovered how much your house is worth.
If it's lower, it can be equally tempting to assume Zillow has undervalued your property.
Neither conclusion is necessarily correct.
Use the Zestimate as one piece of information—not the answer.
If you're considering selling a home in Sonoma County, Sebastopol, Santa Rosa, Healdsburg, Petaluma or the surrounding Wine Country, we'd be happy to take a closer look at the property and provide a more informed, opinion of its current market position. It’s a complimentry service we provide with no obligation to you!
Because when it comes to one of the largest financial decisions you'll make, a computer-generated number is a starting point—not a pricing strategy.
