A water heater's typical life expectancy is eight to 12 years, and the device should be replaced if it leaks, if it fails to heat or if its performance is unpredictable. Problems such as broken thermostats and faulty heating elements can be fixed without replacing the unit.
Gas and electric water heaters typically are replaced with units that have the same power source. Buyers who choose to switch to a different style of heater must have a professional install the new unit and add or remove gas lines. Purchasing a new water heater provides an opportunity to increase capacity, as long as the new device fits in the same space.