What is it?
Combination boilers combine a standalone boiler and a domestic water heater into one device. This allows equipment to be consolidated and high efficiency equipment to do dual duty.
How does it work?
Natural gas is burned to heat water for building heating needs, and the same boiler is used as an “instantaneous” domestic hot water boiler. No hot water tank needed.
What are the most appropriate applications?
Currently, combination boilers are typically used in residential applications. Because they reduce the amount of equipment required, they can save both space and energy in many homes. Commercial applications are limited to situations with limited hot water needs.
What are the savings?
Savings for these boilers typically comes from reduced standby losses (stored hot water in the tank slowly losing its heat before it is used). These boilers are typically condensing boilers, which operate at higher efficiency levels than a standard boiler and can produce additional savings.
What are the non-energy benefits?
Combination boilers have a few benefits beyond energy savings. However, the space savings could be a primary reason people are interested in these boilers. Particularly in space constrained areas, such as apartment buildings, combination boilers can free up space. They may save on first costs and provide many of the benefits of an instant water heater as well.
What is the cost?
These boilers may actually save on costs relative to a conventional condensing boiler and domestic hot water storage option. However, they provide limited amounts of hot water, so customers with large coincident demand for hot water (e.g. restaurants, hospitals, hotels, etc.) may not be good fits.
What is the status/availability of the technology?
This technology is readily available through multiple vendors.
What kinds of incentives/programs are available?
Right now, this technology would typically be evaluated under Custom Rebate programs. Incentives will vary depending on customer specifics, but in general, it takes a project scope of multiple boilers to make a viable Custom Rebate project.