A tank style water heater stores a given amount of water, usually gallons, and keeps it heated to the temperature you set it at, sending it along when you open the water tap. A tankless system doesn’t store the water and heats it only when you need it by means of a series of super heated coils..Lowe’s independent installers have you covered for tankless water heater installations and any other water heater installations your property may require. Why learn how to install a water heater yourself? Tankless water heater installation costs may be less than you think..A plumber charges $ to replace a gas water heater or do it yourself $ and save percent. Adjust the home improvement and repair cost with your ZIP Code..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..