I upgraded to a 50 gallon from a 40 gallon hot water tank. The installer came in and instantly said it would be extra to install. When I asked how much he asked if I wanted him to leave or do the job. I asked him for a rough estimate and he said about $300, including new vent valve on top which they always replace. (should have been in the quote then) It appears that a used flexible gas line was a used piece and the overflow pipe is pulling away from the tank. I called the next day to complain and the guy said he would look into it but never got back to me. The tank was advertised at a local store for $895 and the total cost of the job was $1862.