I am asked several times per month why an appraisal I have completed is not in line with Zillow or Trulia or if the values shown in Zillow or Trulia are accurate.
Zillow and Trulia can give a homeowner a 'ballpark' value of their home, SOMETIMES. If your home is located in a tract type neighborhood where the homes have similar design and build date, you may get a good ballpark value. Locations like Lakewood and Carson in Los Angeles County are good examples of these types of neighborhoods.
However, if your home is outside of what would be considered average condition, the value given by these sites may be significantly different from what the actual value is. Also, if your home is a custom design, large or small for the area, highly remodeled, in disrepair, or located in an area with many differing designs and styles of home, these sites will not be a good indicator of value.
For example, I recently appraised a home in the Belmont Heights area of Long Beach, which is an area with many custom homes of varying designs and styles. This particular home was in very average condition for the area. Zillow has its 'Zestimate' at $1,140,000, however, the actual value is significantly lower.
To know the true value of your home, it is always better to have a licensed appraiser come to your home as opposed to using sites like Zillow and Trulia.