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Using Zillow to Help with Comparables

It’s not a tree, it’s not bedding, it’s Zillow – a free website with an on-line database of almost 90 million homes that estimates property values, and provides sales amounts and other public records.

Zillow’s opening back in 2006 launched a new arena for homeowners to research and evaluate properties.  On their first day of business, there was so much traffic (over 300,000 visitors) that the site crashed.

At their website, Zillow offers a free, do-it-yourself comparable valuation report for both buyers and sellers.  They offer different valuation tools to help homeowners track how much their single largest asset is worth.

Zestimate” provides a rough estimate based on Zillow’s proprietary statistical valuation algorithm – a great starting point to understand an appropriate range of value.  It also offers a “Zindex” – their guess at the median value of your home.

For a more refined estimate, Zillow provides another tool called “My Zestimator”.  It is built around techniques consistent with those of an appraiser.  The user edits the facts that Zillow has on file for their home, and selects what they believe are the best “comps” in the neighborhood.  Zestimator then produces a better estimate.


According to the site, Zillow seeks to provide (and claims) 90% accuracy.  But just how accurate is Zillow?  The Wall Street Journal analyzed 1,000 recent home sales and found that Zillow’s Zestimates were amazingly good – often within a few percentage points of the property’s sales price.  However, when Zillow is bad it can be really bad – off by as much as 25% on one in ten homes.

In property tax appeals, an essential component is valuation and comparables.  Resources such as Property Tax Appeal Guidelines include an appraisal and comps in their structured protest presentation.

Is Zillow the perfect source for comparable valuations for your home?  Probably not.  However, for the price (free) it is a great starting place to get a handle on what you need to prepare for your property tax appeal. 

Michael Korbe