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Combine Water Heating with Space Conditioning and Cut Energy Use in Half

Created 9/2/2015 by Rob Penney
Updated 9/2/2015 by Rob Penney
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Until now, water heaters have been separate from HVAC systems, with different manufacturers, contractors, distribution systems, and end uses. But an integrated heat pump (IHP) provides space heating, cooling, and domestic hot water (DHW) – with one piece of equipment, offering potential for energy efficiency improvements and waste heat recovery. Currently, IHPs are available in the U.S. only as costly custom systems. However, if affordable systems become available here and achieve the predicted 50% energy savings (cutting over a quarter of total home energy use!), this could have a tremendous impact on regional energy use, although it will likely be limited to new construction for the foreseeable future.


U.S. DOE partnered with two manufacturers to develop IHPs that save at least 50% of the energy of a conventional heat pump and electric water heater, appeal to the U.S. market (which prefers forced air HVAC systems), and have competitive prices.


One of these is the ClimateMaster Trilogy® Q-Mode™ geothermal heat pump. The other is an advanced, variable speed, air source IHP developed with Nordyne. This Nordyne system produces hot water for DHW and space heating (hot water fan coil), and uses a refrigerant coil in the air handler for cooling. It allows for heat recovery for DHW in cooling mode. Field tests on the Nordyne system were completed in spring 2015 and the initial product announcement is expected in 2016.


Energy savings vary significantly depending on the type of IHP, application, and baseline system. Modeled energy savings estimates for the Altherma system by Daikin showed approximately 30% HVAC savings compared to a conventional heat pump, but the measured DHW savings were modest (6%), which may be due to sizing and design issues for the application. A Navigant report for the DOE Building Technologies Office estimates that an IHP can reduce HVAC energy use by about 50% (including water heater savings) compared to a 13 SEER/7.7 HSPF air-source heat pump and a 0.9 EF electric water heater. Savings would be substantially higher for a home with electric baseboard heat or a forced air furnace. Field and lab trails of a Mitsubishi prototype DHP Plus H2O multi-split IHP by NEEA showed HPSF ratings for heating of 10 to 11, SEER ratings of 17 to 21, and EF for water heating of 1.8 to 2.3. These efficiencies translate to roughly 50% to 60% energy savings over conventional equipment.


It is difficult to estimate IHP costs because packaged products are not widely available in the U.S., and the systems’ complexity and nonstandard installation practices can increase costs until contractors become familiar with these systems. DOE estimated packaged IHPs have a cost premium of $2,500 to $3,500 over a standard electric heat pump with an electric water heater in a mature market.  However, current custom systems are more costly. 

Air-to-water heat pump systems like Altherma are often custom-built and expensive. In a field test by the Davis Energy Group, the incremental cost of the Altherma system was $19,000 compared to a standard heat pump, electric water heater, and ducted system; the estimated cost premium for air-to-water IHPs in a mature market was $6,400.

The Trilogy geothermal heat pump had a list price of $14,300 to $16,800 in 2013, which did not include the geothermal loop.

The Mitsubishi prototype DHP Plus H2O multi-split system underwent field testing by Energy 350 for NEEA, and a report was released in late August. Costs are expected to be comparable to a DHP system with a HPWH once the market matures.

The NEEA report also cites advantages of eliminating HPWH’s impact on space temperature and inability to operate in cold ambient temperatures without using electric resistance heat. As we get more experience with these systems, we will better understand the performance and market potential of IHPs in U.S. applications. For more information, see the assessment on BPA’s E3TNW.org database of new and emerging technologies and the NEEA IHP report.

Rob Penney

WSU Energy Program

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Sector: Residential
Function: Emerging Technology