We did not do shit to improve our old house in Texas from when we bought it 2016 to when we sold it on 2025, the appraised value went from 195k to 331k. Its based on sales of similar houses in the area and (theoretically) capped at a 10% increase per year assuming you have a homestead exemption. They can also do cap loss recovery for some period of time after appraisals stop increasing to recoup the “lost cap” from years when there was a greater than 10% increase but the homestead exemption prevented them from getting all of it.