How much should my ADU increase the value of my property

[David Yee]

Hello! I currently live in a 1,000 sq ft home on a 7,000 sq ft lot in San Diego county. I am building a 1,000 sq. ft ADU in my backyard. The appraiser from the bank lending me the money for the project said my home would increase in value from $850k to $1.1 million once the ADU is put in. Does this sound correct? I thought my property would increase in value more than that; especially if an investor were to buy it.

Thank you in advance!