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The time it takes to install or replace a water heater depends on the type of heater and the complexity of the job. A professional can typically replace a standard tank-style water heater in one to three hours. However, if the work area is tight, such as a small closet or crawl space, the job could take four to five hours. Replacing an existing tankless unit takes about two to three hours, while upgrading from a tank-style to a tankless water heater is more complex and can take four to six hours. The project will take longer if you are switching fuel sources, such as installing a gas heater which can add about an hour to the timeline, or if the unit needs to be relocated.

In most municipalities, a license is not mandatory for water heater installation or replacement. However, we strongly recommend hiring a licensed plumber or water heater installer to handle the work. Licensed installers are far less likely to make a mistake during the installation, which means paying for the experience decreases your risk of a leak and other issues. You can use our state licensing tool to find out if a contractor you’re considering in your area holds a plumber’s license.

Installing a water heater without a permit can result in high fines—as much as hundreds of dollars per day, in some areas. It can also void your homeowners' insurance and cause problems when selling your home because it violates local building codes and safety regulations.

Yes, you can replace a current tank water heater with a tankless model or vice versa. If you’re maintaining the same fuel source—gas or electricity—the switchover should be smooth. A conventional tank requires open floor space, while a tankless model can be wall-mounted. If you’re switching to a tank water heater, you might need to clear space for it. Gas-powered tankless water heaters need a large volume of gas when they start running to heat the water instantly. You might need to increase the size of the gas line when going from a tank to a tankless model.