Automated tools like Zestimates are built on broad data sets that average across an entire zip code. In Southbury’s case, that zip code, 06488, includes Heritage Village condos, standard single-family homes, and larger acreage properties that all price very differently from one another. When the algorithm mixes those together, the output can be off by a meaningful amount in either direction. On top of that, automated tools can’t see inside your home, they don’t know about a finished basement, a renovated kitchen, or a newer roof. A Comparative Market Analysis uses actual closed sales of homes that are genuinely comparable to yours, which gives you a far more reliable number to work from.