Residential Combi-system Field Demonstration Opportunity

A typical installation offers:

  • Significant space-saving potential – less piping
  • 41% annual energy savings in California
  • Gain points on your Title 24 EDR
  • Easy Maintenance
Combi System Courtesy CenterPoint Energy

Photo: CenterPoint Energy

Figure 1: Typical combi-system installation in constrained space

Combi-systems are comprised of a condensing tankless water heater (TWH) and an air handler unit (AHU) with a hydronic coil for space heating as shown in Figure 2. The AHU is similar in form factor and heating capacity to a forced-air furnace, and therefore can easily replace a furnace. A combined space and water heating (combi) system uses a single heating appliance to produce domestic hot water and space heating. They can be installed with your cooling system of choice, and paired with integrated ventilation too.

Did You Know?

Numerous manufacturers offer combi options. These systems have been proven in California to outperform traditionally separate furnaces and water heaters. Combi-systems are commercially available to serve homes with heating capacities from less than 10 MBH to more than 60 MBH.

Combination space/water heating (combi-) systems offer significant benefits to new home builders.

  • Smaller footprint
    • Closet sized mechanicals
    • Increased living area square footage
  • Reduced infrastructure cost savings
    • One gas line
    • One set of venting
  • Increased comfort by matching heat generated to demand
  • Increased energy savings up to 40%*
    • Marketable $ savings for your homeowners
    • Opens up performance path trade-offs to meet Title 24
  • Builders will be compensated to purchase, install, and maintain equipment


* Savings relative to an 80% AFUE furnace and 0.64 UEF water heater


Advantages of combi-systems

  • Less labor hours and material: Home only
    needs a single gas line and exhaust vent for
    tankless water heater
  • Single penetration through exterior envelope
  • Equipment modulation—streamlined, better
    comfort space/water heating
  • Higher efficiency compared with tank water
  • Smaller footprint—give your homeowners
    more space
  • Proven technology from reputable
    manufacturers, little risk

Builders Wanted!

GTI, a leading independent research, development, and training organization, is conducting a pilot to install combination space/water heating systems in Southern California. This project will showcase market-available water heater and hydronic fan-coil combinations in new construction single-family homes.

The team is recruiting builders in the Southern California area to participate in the project.

Builders will be compensated to purchase, install, and maintain one of the combi-system technologies from a list of qualified equipment, install instrumentation equipment, and assist with tasks to monitor energy and water usage.

Contact Us to Participate

Please reach out to Jason LaFleur,, (847) 768-0765
for more information.