There are three main things you may want to replace your heater for, and those are age, issues, and efficiency. You can learn more about what each of these things involves, what to consider with each one, and more about these topics by reviewing the information here. Replacing your heater due to its age Deciding when to replace your heater as it ages isn't always such a cut-and-dry decision. Even if your heater is getting older, you may not want to replace it yet if it is still doing a great job and hasn't needed any repairs.