I am not totally sure how accurate it is, but they report to use some formula related to what similar houses in your area are selling for.
I hope you are right that it is worth more. I hear that some areas of the country are going up in value.
We bought our house in 2005 for 250 thousand. Zillow now estimates for us that it is worth 142 thousand. That may seem horrible, but a year ago, it was only 132 thousand. It is inching back up slowly, but at that rate, we’ll be lucky for it to be back up to 250 by the time we retired in 20 years. We owe about 197 thousand on it so selling our house would be totally out of the question.