Five types of water heating technologies are eligible for Energy Star qualification, including one of the newest types that hit the market in 2010.
The latest to join the energy-saving list is the condensing water heater. These heaters, fueled by natural gas, are a new twist on the old technology that offers increased energy efficiency and lower utility costs.
In addition to the new condensing water heaters, the other types of water heaters that can qualify for the Energy Star label are:
- Gas storage
- Heat-pump hybrid
- Whole-home tankless
To qualify for an Energy Star rating, a water heater must be tested by an independent testing company to deliver significant, measurable energy savings.
How do they work?
Gas condensing water heaters operate much like regular gas water heaters in that water is heated by a gas burner. A condensing unit may have a storage tank or be a tankless, on-demand design.
With a condensing heater, there’s one major difference that significantly increases efficiency and performance. Instead of venting the combustion gases directly outside, those gases are captured and utilized to heat the water more quickly.
A standard gas storage water heater is like a water tank sitting atop of a gas fireplace with the chimney running straight up through the middle, exiting at the top.
A gas condensing water heater's chimney or flue is designed with a greater surface area. The heat and combustion gases have much farther to travel before they exit the water tank, so more heat is transferred to the water in the tank.
A.O. Smith offers a condensing tank unit in its Vertex line of water heaters that offers up to 96 percent thermal efficiency. Because it’s so efficient, the tank can be smaller than other units. However, it can deliver continuous hot water for heavy-demand households.
Rinnai Corp. added condensing technology to its line of residential tankless water heaters. Like the tank heaters, Rinnai’s condensing tankless water heaters recapture residual heat from flue gases and transfer it into the water being heated.
Rinnai’s condensing design incorporates two heat exchangers to achieve optimum water heating value from every cubic foot of natural gas or propane. Rinnai said the Energy Star-qualified units offer up to 95 percent thermal efficiency, which translates to significant energy savings when compared to traditional gas tank water heaters.
Why are they better?
Choosing an Energy Star-qualified gas condensing water heater instead of a standard model can save more than $100 a year in utility costs. That's more than $1,000 over the expected lifetime of the water heater. Larger families can save even more.
The efficient heating means homeowners can enjoy a nearly constant supply of hot water. Because gas condensing water heaters are so efficient at heating water, the tank heats up almost as quickly as it's filled. There’s no more waiting for the water to heat up after heavy use.
For more information, see our Water Heaters Research Center.