Heating with Tankless Water Heater & Hydronic Air Handler vs. Gas Furnace


I've looked around online and haven't found a lot of good information on home heating with hydronic air handlers used in conjunction with tankless water heaters (TWH). I would be interested to hear from anyone who has experience with these "combined" or "integrated" space- and domestic water heating systems.  I'd like to know a few things, especially as they compare to a condensing gas furnace:

- How efficient are these systems?  I've read that they match the efficiency of the water heater, so if you have a 94% efficient condensing TWH, your home heating is then 94% efficient as well. Of course, this does not mean that they necessarily heat as effectively as a condensing gas furnace, since the heated air from these systems is not as warm as that from a gas furnace, correct? 

- What are your thoughts on ease of installation and ongoing maintenance requirements? I have heard of issues with scaling, and a need for very frequent cleaning of the inlet strainer to the TWH.

- When the water from the air handler is returned to the TWH it is much warmer than typical incoming water to a TWH.  It is my understanding that higher incoming water actually reduces the efficiency of a condensing TWH - is this still true with current condensing TWH models?

- Bottom line, would you put in one of these systems, or opt for a separate condensing gas furnace?  Are there situations when you would choose one over the other?

I'm interested to know more about these systems in general, but also have a specific home in mind: a 2400 sf home in Portland, OR built in 1928 (currently with little insulation), that has a condensing TWH already installed.

Thanks for any insight you can offer!

- Chris

Views: 9315

Reply to This

Replies to This Discussion

When it costs the same price as 2 separate systems there is no juice regardless of how hard you squeeze.

Only a nightmare for future service techs, there will never be a part on the truck to fix the system, maybe not even at the supply house. Parts for tankless water heaters are special order, and not every tech can work on them.

I've looked at tankless water heaters and I'm not seeing any juice for the squeeze there either. They simply don’t' save enough energy to justify their high upfront installed cost and more complex maintenance/parts availability.

As you have pointed out, on a tight house is it even worth paying an ever increasing monthly fee for the gas meter charge, or just go all electric? Our local electric company gives cheaper rates in the winter, cheap enough that 3/4 of all-electric homes use RESISTANCE HEAT as a primary heating method.



  • Add Videos
  • View All


Latest Activity

Amber Vignieri commented on Amber Vignieri's blog post Even with Polar Vortex, Hourly Pricing Participants Saved
"Thanks for your comment Bob! We couldn't be more excited about the increasing prevalence of…"
1 hour ago
Home Energy Magazine posted a blog post
19 hours ago
Noah Ray Sanders replied to Steve Mann's discussion TEC Blower Door Frame in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"If so please contact me 8329717862 or email noahraysanders@hotmail.com"
23 hours ago
Noah Ray Sanders replied to Steve Mann's discussion TEC Blower Door Frame in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Do you still have the frame?"
23 hours ago
Noah Ray Sanders replied to Joe Urycki's discussion TEC blower door and UEI combustion analyzer for sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Do you still have equip?"
23 hours ago
Noah Ray Sanders joined allen p tanner's group

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
23 hours ago
Tom White's video was featured

Retrofitting Vintage Home for Energy Efficiency

A presentation by Greg Labbé in April 2014 on retrofitting vintage home for energy efficiency. He talked about basic building science, brick houses, movement of heat energy and moisture in and out of the house, air barrier and water barrier, house…
Sam Goode is now a member of Home Energy Pros

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service