Harris County Appraisal District Values Off By 20% For One In Six Houses Harris County Appraisal District (HCAD) Values Are Much Less Reliable For Older Homes Than For Homes Built After 1990. For Homes Built In 1990 Or Later, HCAD Is Typically Within 8% Of Market Value. However, The Error Rate Is 20% For Homes Built Before 1960, 18% For Homes Built Before 1970, And 15% For Homes Built Before 1990. Including All Homes, HCAD’s Valuation Error Rate Is Typically 14%. HCAD’s Value Is Off By 20% Or More For About 15% Of All Homes In Harris County.
HOMES IN HARRIS COUNTY
Year Built
Typical HCAD Error Rate
Before 1960
20%
Before 1970
18
Before 1990
15
1990 or later
8%
Harris County Appraisal District uses a process termed mass appraisal to value the 1.7 million tax parcels in Harris County. A licensed appraiser doing an appraisal for a home is usually accurate within 5 to 10%. Appraisal is not an exact science; it involves much judgment. Further, there is limited information available regarding the subject property and comparable sales even when doing an individual appraisal.