There are a number of free computer-generated valuation systems online that are drawing sellers' and buyers' attention. Zillow, based in Seattle, is a current favorite. The question is whether the values arrived at are accurate. The answer is: it depends.

According to an article in the Wall Street Journal, valuation estimators such as Zillow work best if you are looking at homes in the mid-range of prices where there are many similar homes in a neighborhood. But if a seller is relying on Zillow to arrive at a purchase price for a higher-end home, or one that has a lot of quality remodeling, the value is other than accurate.

Computer-generated valuatin sites don't make allowances for high-value amenities, such as being in a security gated-community, or being built with high-quality materials. Nor can they judge factors such as layout and appeal. If a home in a particular neighborhood has undergone extensive interior remodeling, and upgrading, it's true value will be higher than other homes in the area. Zillow doesn't  know lender requirements for loan appraoval, which often require that certain types of properties are included in a real appraisal. Computer-generated valuations can't think, and there is no substitute for a professional real estate agent when buying or selling a home.

An appraiser who is familiar with the ever-changing market can accurately determine a value by including interior and exterior amenities, quality of construction, remodeling, as well as market trends. Yes, there is an appraisal fee, but it is far less expensive than losing thousands of dollars from a home sale that was under-priced.