If your boiler is more than 16 years old or if you recently improved your home’s insulation and air tightness, you should consider replacing your old boiler with a more efficient one. With high energy prices, homeowners seeking to greatly reduce their energy use may want to consider installing a condensing boiler, which have efficiency ratings of 90 percent AFUE (Annual Fuel Utilization Efficiency) and higher. Depending on the age of the boiler you are replacing, it could be 15 percent to 45 percent more efficient than your current model. Your boiler’s AFUE tells you how much energy is being delivered as heat to your home. For example, a 90 percent AFUE rating means that 90 percent of the heat generated by the boiler is being used to warm your home, while the other 10 percent escapes in the combustion gases that are vented out of the home.
How It Works
Condensing boilers can achieve greater efficiencies because they capture more heat from the exhaust gases than a conventional boiler. To do this, a condensing boiler has a larger heat exchange surface to enable it to transfer as much heat as possible from the boiler's burner into usable heat, thereby allowing less heat to escape as exhaust gases. When the combustion gases flow over the heat exchanger surface, they condense, which means they cool to a point where the water vapor in the gases changes to liquid.
What to Consider Before Choosing
When replacing your boiler, it is important to work with a qualified heating professional to help you decide which product is right for your needs. A heating professional will determine the proper size boiler and help you choose the level of energy efficiency that makes the most economic sense for you.
The size of the recommended boiler will depend on the size of your home and many other factors that impact your home’s heating requirements. If you choose a boiler that is too big, it will waste energy. This is because it will cycle on and off too frequently. If it is too small, it won't provide enough heat to your home. If you are replacing an existing boiler, it is still important for your installer to perform a load calculation to size your new boiler, because the old boiler could have been improperly sized or you could have made improvements to your home that would impact the boiler’s size requirements.
In addition, you should always choose a boiler certified by the Air-Conditioning, Heating and Refrigeration Institute (AHRI) and listed in the AHRI Directory of Certified Product Performance
. To find manufacturers of residential condensing boilers in the directory, select "Boilers" under the Residential product category, then select "Advanced Search." On the search screen, find the field labeled "Condensing Type" and select "Yes" from dropdown menu. To narrow your search further, you can enter additional information in the other fields such as a minimum or maximum AFUE percentage or Fuel Type. Ask your installer to provide you with an AHRI Certificate of Product Performance that can be printed from the AHRI Directory of Product Performance
. This certificate contains the boiler’s certified performance ratings and can be used to obtain tax credits as well as rebates and incentives offered by your utility or other local energy efficiency programs. .
Proper Maintenance Key to Maintaining Efficiency
After the installation is complete, keep in mind all heating equipment, including condensing boilers, need periodic maintenance. Typically, the heat exchanger and condensate traps need to be cleaned on an annual basis by a qualified heating professional.