Behind the scenes the model pulls comparable sales, applies statistical adjustments for square footage, bedroom count and lot size, then produces a range it presents as a single number. Confidence intervals on these tools routinely run 10 percent or more in either direction, which on a $400,000 house is a swing of tens of thousands of dollars.
What the model cannot see is the actual condition of the house. A basement finished without a permit, a rewired electrical panel, or a kitchen renovated last year with invoices to prove it are exactly the kind of documented improvement that never reaches the property records these sites draw on from Information Services Corporation.
Use the estimate as a starting curiosity, not a number to list against. Joel Dyck's hand-reviewed valuation walks the property, checks the permits and prices it against genuinely comparable sales rather than a statistical average.