How Accurate are Zillow's Free Home Appraisals?

Are Online Home Price Estimates Reliable?

The thinking by some is that a real estate agent has a conflict of interest. He or she wants to close a deal and earn a commission, and that generally means persuading a buyer to bid more and a seller to ask less. It’s just common sense that a disinterested party will come up with a fairer market valuation. But "disinterested" does not always mean "fully informed."

Zillow has become “the Google of real estate” by promoting that rationale. Founded in 2006, the company receives millions of online queries. The site allows users to enter an address or zip code to retrieve listings of homes that are on the market with asking prices. It also provides “Zestimates” of the market value of listed homes and surrounding homes that are not on the market. Key details are included, such as square footage, lot size, number of bedrooms and baths, photos, taxes, school district, etc.

Sellers and shoppers rely heavily on Zestimates, and that makes life difficult for real estate agents. Zestimates “are the bane of my existence,” said one anonymous agent on an industry blog. People tend to take Zestimates as gospel, and argue with the real estate agent’s valuation of a property. Such disputes are killing a lot of deals, say some agents.

Zestimates “are a good starting point,” according to Zillow CEO Richard Barton. Zestimates have “median error rates” ranging from 2.4% to 7.49% depending on your locale. (See Zestimate median error rates for major metropolitan areas.)

On a typical San Francisco home worth $1,379,000, that could be as much as a $102,613 disparity -- not exactly chump change, but perhaps not a deal killer in a pricey seller's market.

A Real Estate Distortion Field?

Apple is so good at marketing their products that some people have joked that they use a "reality distortion field" to persuade consumers that there is no alternative to their brand. In similar fashion, the popularity of Zillow may be creating a real estate distortion field.

Real estate brokers all over the country have done their own studies comparing Zestimates to actual sale prices. One real estate agent found Zillow underestimated the final selling price up to 70% of the time, by as much as $70,000. In 25% of sales, the Zestimate was higher than the contract price. (So 5% of the time, Zillow got it right.) In another ZIP code, Zestimates were off 100% of the time, by as much as $190,000.

On the flip side, Zillow's home price estimates seem to reflect reality pretty well in my town. That could be because it's a very active real estate market, so there's a lot of current data (actual sales prices) on which to base estimates. If you want to estimate what a home is worth right now, you need to look at recent sales of comparable nearby homes. That is what real estate agents do every day.

Zillow does provide an interactive map which shows nearby homes that are sold, or listed for sale. But it's very difficult for a computer program to understand which of those homes are truly comparable to yours, or the one in which you are interested. Matching up homes with similar square footage, number of bedrooms, etc., may not take into account the fact that one home had a recent kitchen remodel, a new roof, or other important factors in determining the value.

The moral is that Zillow estimates should be just one factor in determining the value of a home.

Zillow does let you login and claim your home, so you can update any information that's not correct. I did just that when preparing to sell my home 7 years ago. Zillow had the number of bedrooms and square footage wrong, so when I changed those numbers, the Zestimate jumped up accordingly. You can also list your home as "for sale by owner," upload photos, and set a price you think is fair, given current market conditions. I'm certain that helped me get a top dollar offer, in just days, without needing a real estate agent.

Other Home Value Estimators

There are other online real estate price estimators, including Eppraisal, Redfin, and the Chase Home Value Estimator. They all rely on data pulled from local government records, which are often outdated, incomplete, or inaccurate.

But they must use other factors as well, because if you query each one of them, you'll get different estimates for any given property. The good news is that most of them allow you to login, claim your home, and update the details if they're not correct.

Have you checked the estimated value of your home using one or more of these tools? Your thoughts on this topic are welcome. Post your comment or question below...