I use 5 Sold 5 Pending and 5 Active (If Available) from the Realtor Controlled MLS data to determine a price per sqft value from low to high with in a measurable sqft of the subject house and property.

EzValue uses a data source algorithm which determines value based on it own automated valuation. 

Realtor.com uses a data source algorithm which determines value based on it own automated valuation. 

Zillow uses a data source algorithm which determines value based on it own automated valuation. 

Redfin uses a data source algorithm which determines value based on it own automated valuation. 

This is the counties valuation of your property that determines how much you pay in annual property taxes.