Automated home evaluators are fun to use, giving you key neighborhood and property data related to the home you want to sell or buy.

Accurate sales data is a crucial element of the home evaluation tools made available by third-party companies such as Homeadvisor.com, Realestate.com, and Homegain.com. They work well in most cases, but if you are in a non-disclosure state (a state which does not require the public posting of sold data,) or a county without automated tax roll services, online home evaluation tool results can be misleading. If they can't always get "sold" information, how do they come up with evaluations?

Using their own technologies or relying on third-party data aggregators to get property information, these companies glean data from sources as diverse as local government agencies and taxing authorities, the labor department, third-party economic and demographic companies, and all the way to the National Association of REALTORS and the U.S. Census Bureau.

The accuracy of the data is also affected by the speed and cooperation of these sources to release and share this data, which can take as long as three months in some cases. In addition, each company may have additional proprietary evaluation methods that they use to complete the numbers, and that can also mean differing results.

Using the same sample home, 6206 Saratoga Circle, Dallas, TX, 75214, results from Homeadvisor, Realestate.com and Homegain illustrate these differences.

Homeadvisor returned the best results for a calculated sales price based on sold comparables within the same zip code - $182,826 to $245,620. Homeadvisor also showed homes that are currently for sale, but there were no sold comparables of the immediate neighborhood, even though eight homes had sold within a four-street radius since January 2000.

Realestate.com returned a general property analysis report but wisely declined any "value" report, citing unavailability of data. That's fine, since Texas is a non-disclosure state.

Homegain returned a report with the widest range, but most of it was not applicable. No results were returned for the immediate neighborhood, nor were results even returned for the same zip code. Comparables ranged from .58 to over 1.81 miles away. The homes ranged from $68,000 to over $1.3 million, for an evaluation estimate range of $299,250 - $303,525.

The Saratoga home was also evaluated by a local Realtor and a bank appraiser, and their results compared to a recent tax roll appraisal.

• Realtor's CMA: $251,460 ($99 per sq.ft.)
• Bank appraisal: $189,000 ($74 per sq.ft)
• 2001 Tax assessment: $184, 500 ($73 per sq.ft.)

According to the Realtor, recent solds ranged from $99 a square foot to $133.96 per square foot, reflecting updates. Of the active homes, the range is $124 and $130 per square foot, One home, 6171 Saratoga Circle, is offered at $109.65 per square foot, and backs up to an electric railroad track. She priced the Saratoga home slightly under the market because the extra square footage was due to a garage conversion, making the house larger than comparables.