Most California homeowners pay between $2,200 and $3,800 for a standard 40-gallon gas tank replacement installed by a certified professional, and $2,400 to $4,200 for a 50-gallon unit. Tankless installs run higher, typically $4,500 to $7,500. These ranges include the unit, labor, permits, and haul-away of your old unit. We give you an exact upfront price before any work starts.