AVM's, or Automated Valuation Models, can be used as a guide to give a person an idea as to how much a home may be worth. Sometimes these can be fairly accurate, however most of the time these models are not very accurate. Without someone actually going out to ones home and physically inspecting the property there is no way to provide an accurate estimate as to how much your home is worth. You may have the nicest house in the area and this may make your home worth a little more than everything else in your neighborhood. On the other hand you may have the worst house in the area and your home may not be worth as much as any other house around you. Actual appraisals make adjustments for all kinds of things. If you have a pool, a huge stamped concrete patio, added an addition that does not show up in the county records, lost part of your home to a fire, etc.... these items will have an impact on the final value of your home, good or bad. Therefore, without actually having someone come out to your home there is no accurate way to provide an estimate as to how much your home is worth.

The accuracy of an AVM depends greatly on the density of the homes in your neighborhood and the number of recent sales.
If you are in a rural area or if your home is particularly unique then do not count on an AVM to be very accurate.