It is completely worthless in neighborhoods that have very low turnover.
It also seems to factor in list prices for the neighborhood – so if a neighbor lists his house for a completely pie-in-the-sky high price, the zestimate for the neighborhood goes up. When they sell at a realistic price OR pull it from the market, it seems to settle back down.
It also does not take into account issues that can swing a sales price like interior remodels (or lack thereof), view or landscaping, etc…
At times, seems to be entirely random. My house was listed with a zestimate 300k below what it is currently zestimated at. The first price was ridiculously low, the current price is probably higher than we could get. When we refi’d last year we had an appraisal – that price was in the middle.
