How online services priced my house
By Holden Lewis • Bankrate.com

Some people are bewildered by Zillow.com's estimates. Why, my mom asks, does Zillow say her house is worth $120,000, but the similar house next door is worth $180,000? A Bankrate colleague says Zillow overestimated his home's value by tens of thousands of dollars.

When I looked up my home, Zillow's estimate looked accurate, in my seat-of-the-pants judgment. Fortunately, I live in a place where I can get a second opinion, from Homekeys.net.

Initially, Zillow said my home was worth $339,663. But I have a new roof, and Zillow compared my house to, among other places, some two-bedroom condos and tiny town houses. After using the "My Zestimator" tool to update the roof's condition and ignore the dissimilar comparables, Zillow estimated my house to be worth $357,033.

That seemed high for the neighborhood, so I checked Homekeys, which gives estimates on home values in just three South Florida counties, including mine. It initially estimated the value at $351,200. I threw out a bad comparable that skewed the value, guessed that my new roof was worth $3,500 to a buyer and that the pool was worth nothing, and Homekeys' adjusted estimated value came in at $355,200. Homekeys' site design makes it impossible to link to a specific property estimate.

At $357,033 and $355,200, the difference between the estimates comes to one-half of 1 percent. Either both estimates are pretty darn close, or they're both inaccurate in the same way. Occam's Razor says they're fairly accurate.

But I wouldn't know for sure unless I put the house on the market and struck a deal with a buyer.