People are constantly arguing over how accurate Advanced Valuation Models (AVMs) like Zillow or Eppraisals really are. To me it doesn't matter, they are just another tool to help potential buyers understand the current Real Estate Market. I personally find AVMs fascinating since I only have a general understanding of their algorithms and how they come to the conclusions they do. While I don't always find them to be correct, I do think they're helpful when contrasted with other market information

This page simply compares their valuations against what the current for sale inventory says and then averages them all. Most of the time the findings are pretty interesting.