Condensing Boilers – What Are They & Why Are They So Efficient?

November 30, 2016

At Mass Save, we are constantly working on ways to save you time, energy, and money by offering advice and finding you rebates. We want to make sure you get the most out of the energy you use, and you want to make sure you get the most out of the money you spend; put the two of us together and you’ve got a recipe for a green earth and extra green in your wallet!

Today we bring you another wonderful way to save energy and money by means of condensing boilers.


What Are Condensing Boilers?

Conventional boilers lose latent heat and flue gas heat up the chimney, making them only about 80% efficient. Condensing boilers capture that heat by cooling the escaping water vapor below its dew point, leading to efficiency of around 95%. They can also modulate, putting out less heat during the warmer temperatures in the spring and fall, and therefore using less energy. However, in order to do this, they need to know what the outside temperature actually is, so make sure your contractor also installs outdoor reset controls that enable it to modulate.

How can you get the most out of your condensing boiler?

  • Set it and forget it - Set your thermostat to a comfortable indoor temperature and let technology adjust your boiler’s water temperature in response to the outdoor temperature. It actually functions better without dramatic setbacks.
  • Consistent temperature - Don’t be surprised if your radiators or baseboards don’t seem as hot as they once did. Since your boiler water temperature is lower during milder parts of the year, your distribution system may be cooler, but your indoor air temperature should remain consistent.

How can condensing boilers save you money?

When the time comes for you to switch your old boiler (which is a good idea if it’s more than 15 – 20 years old), your best bet is to go with a condensing boiler. They have the potential to save as much as 40% off your heating costs annually and you’ll start noticing the difference on your bill from day one. If that isn’t enough, Mass Save has rebates specifically for homeowners who are making the switch from regular boilers to condensing ones—up to $3,500. Check them out here.

Not sure if you are due for a new boiler? Schedule a no-cost Home Energy Assessment with us, and an Energy Specialist will help you determine if your heating system needs replacement. Visit for more details.

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