The cost to Replace a Water Heater starts at $, $, per heater, but can vary significantly with site conditions and options. Get fair costs for your SPECIFIC project requirements. See typical tasks and time to replace a water heater, along with per unit costs and material requirements. See professionally prepared estimates for water heater replacement work..How much replacing a water heater should cost. Average costs and comments from CostHelper’s team of professional journalists and community of users. With all needed parts and labor, hiring a plumber to install a traditional gas water heater costs $ $, or more, depending on capacity with gallons the most common sizes length of warranty typi.y years and the amount .I’d say straight replacement without having to replace other components or having to bring up to code cost of water heater plus hours labor. Pans to go underneath are not needed unless leakage can cause damage to the building. In a ba.t I would not put a pan under unless it was on a wood floor. You need to pipe the pan drain somewhere .A member of our team will you to discuss your water heater repair needs and schedule an in home repair appointment..