There are many different kinds of hot water heaters, so the Energy Star site is a good bet for info. It’s very specific on what is and is not credit-eligible. For instance, it must have a thermal efficiency of at least 90%. 

Don’t rely solely on contractors who may not know the details or who promise their products will get the credit in order to make a sale.

Read on to learn if you qualify for the tax credit:

Savings, cost, and payback period
Advantages of tankless systems
Other types of water heaters
Think smart for a new water heater