Rethinking Heat Pump Water Heaters

New fact sheet reviews how electric heat pumps cost more to own and operate than tankless systems.

Previous articles published in the Propane Energy Update have argued that high-efficiency propane tankless water heaters outpace comparable electric heat pump water heaters (HPWHs) in terms of installation and energy savings, heating performance, and emissions reduction. A new fact sheet published by the Propane Education & Research Council summarizes the research basis for those arguments, which can train construction pros to answer questions from customers trying to decide between the two water heating technologies.

Four reasons to choose tankless
Propane tankless water heaters are cheaper to install. That's because accommodating an HPWH's exacting installation requirements comes at the cost of additional materials and labor. On average, in scenarios modeled by the research study (PDF), HPWHs cost 34 percent more to install in new homes and 18 percent more in retrofits. These costs increase if the surrounding space must be enlarged or the unit vented.

 

Tankless systems deliver better long-term value. Although HPWHs cost about $40 less to operate annually, the full cost of ownership was 18 percent higher in new homes and 13 percent higher in retrofit projects, according to the study. This is because tankless units last longer: about 20 years, compared with 15 years for an HPWH.

Tankless units perform better. They provide hot water continually and at flow rates three times that of HPWHs. For new-home buyers or remodeling customers who have lived with undersized storage systems, the prospect of never running out of hot water would be worth the additional cost, if there were any.

Propane tankless units lower the carbon emissions produced by water heating systems. This may surprise those who associate gas-fueled operation with high carbon dioxide (CO2) production. But as long as the upstream electricity that powers HPWHs comes primarily from coal-fired plants — which is true in many states — HPWHs are the more carbon-emissive technology: an average of 39 percent more, according to the research study.

The reputation for efficiency and environmental sustainability that precedes HPWHs does not always survive analysis. See for yourself by downloading the fact sheet as well as the full water heating study.

You can also calculate the energy cost and carbon emissions rate of a new or existing water heating system being installed in your area by using the Heating Energy Cost and Carbon Calculator.

For more training content about tankless water heaters, check out one of the free online continuing-education courses about propane water heating systems at propanetrainingacademy.com.


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