How Redfin and Zillow Value Your Home
If you search "how much is my house worth?" online, you will get dozens of hits, showcasing the top home value estimators. According to NerdWallet, 22% of homeowners in the United States determine the value of their home using this method. The technical term for these tools is "automated valuation model."
Two of the big players in this space are Redfin and Zillow.
These tools leverage the data available from public records, such as tax assessments and property transfers. Using mathematical modeling, these tools aim to predict the value of your home based on the most recent listing prices and sales in your area.
Both companies are transparent concerning their national median error rates. For example, Redfin reports that its current median error rate is just 2.72% for houses for sale and 6.79% for off-market homes. This means that the estimate is within these margins of error half the time. So, for when a home is on the market and sells, Redfin's estimate will be within 2.72% of the sales prices half of the time.
In comparison, Zillow reports that its national median error rate for on-market homes is 1.9%, and for off-market homes, that error rate increases to 6.9%.
The issue here is that a median national error rate does not represent your local market. So, the error within your local real estate market may be better, or far worse, than the advertised national medians.