Electrification is coming to water heating too. Following in the footsteps of the automotive industry, gas products seem to be in their final phase before a purposeful phase-out due to sustainability concerns. States like New York and California have already banned the use of natural gas in commercial buildings.
Heat pump water heaters have regained prominence as a promising future-oriented technology. Essentially, heat pump water heaters transfer heat energy from one source to cold water. By relying on the transfer of energy instead of its generation like standard water heaters, they can have efficiencies of more than 100%. Hence, they can prove to be a robust, environmentally friendly water heating choice that can save energy, and utility bills. However, with not enough past data, and lack of adequate standardization, heat pump water heaters can be difficult to compare.
In this article, we will take a look at multiple heat pump water heaters sold in the United States for commercial applications. We will attempt to draw a fair comparison with comparable data available to us so that you can make the best choice for your commercial property.
To enable a fairer comparison, we have divided the commercial heat pump water heaters available into two categories: high-strength commercial heat pump water heaters and moderate-strength commercial heat pump water heaters. It is vital to know that manufacturers usually offer different models with varying strengths to offer consumers an ideal choice for their unique needs. Our categorization is not an indication of their favorability.
We will also be including two of our own units – the Electron iE1 and the Electron iE6 in this comparison. However, it ought to be noted that the Electron series cannot be evaluated in the same manner as the other heat pump water series since it is tankless. All other heat pump water heaters use a tank-style design with the need for large storage tanks. Hence, comparing the Electron Series with the tank-style options would be unfair for the Electron as well as the other models. Let’s look at some basic comparison metrics for both the categories and then delve into understanding what these mean in terms of a tankless versus tank-style heat pump set up.
It ought to be noted that the Electron series cannot be evaluated in the same manner as the other heat pump water series since it is tankless. All other heat pump water heaters use a tank-style design with the need for large storage tanks.
Please note that the information used in this comparison was obtained via the manufacturers’ website and the product’s literature. No third-party data was used in order to maintain fairness and assess the claimed metrics as opposed to on-field metrics. Click on the links below to access more information about each of the products mentioned on their official webpages:
Tank-style heat pump water heaters use a heat pump to heat water and store it in a tank. On the other hand, a tankless water heater heats incoming water on-demand without storing it in a tank. The most visible effect of this difference is the consumption of space. The metrics shown above only depict the dimensions of the heat pump units. However, properties using a tank-style heat pump water heater would also need to account for space requirements of storage tanks, mixing valves, swing tanks and other components. For the case of tankless heat pump water heaters, if a property opts for the high-strength commercial heat pump option (Electron iE6), they will need to account for space needed by the thermal battery.
For instance, a 250-gallon storage tank typically measures 70x50x52 inches (HxWxD). A 500-gallon tank typically measures 82x60x62 inches. Moreover, with tank-style water heaters, you would also need a swing tank, a loop skid, in-line boosters or electric storage tanks, depending on the application. For instance, multi-story buildings with high pressure requirements would need at least two separate booster pumps.
The thermal battery (Electron iB3) that forms the only additional component for a high-strength, tankless commercial heat pump water heater like the Electron iE6 measures 70.8×30.5×94.5 inches.
While energy efficiency is a good indicator to adjudge energy usage and cost savings, it can be misleading when comparing tankless and tank-style water heaters. A tank-style heat pump water heater would typically operate all the time to keep the water stored in a tank constantly hot. A tankless heat pump water heater, on the other hand, would only consume energy when there is a hot water demand since it does not store water.
Let’s take an example. Say a tank-style heat pump water heater has a COP of 6 while a tankless heat pump water heater has an efficiency of 4. Essentially, one unit of electricity would yield 6 units of heat energy every hour.
A tank-style water heater would run all day yielding 144 units of heat energy in 24 hours while consuming 24 units of electricity.
A tankless water heater would only run when there is a hot water demand. Even if we consider an example that is lenient for tank-style water heaters, the tankless water heater might run for half the day. It would consume 12 units of electricity and deliver 48 units of heat energy. In reality, a tankless water heater would run for a much lower aggregate time than 12 hours each day.
In the above example, the tankless heat pump water would save the property 96 units of energy despite having lower efficiency. It does appear that the tankless heat pump water would deliver lesser heat energy in this example. However, tank-style water heaters typically need to consume more energy since they need to keep the water stored in the tanks constantly hot. A tankless water heater would only require a fraction of that energy since it only needs to operate when there is a hot water demand.
Additionally, some other external components of a tank-style heat pump water heater like electric storage tanks would consume more energy and result in higher operational expenses as well.
When it comes to refrigerants, it ought to be noted that the R744 CO2-based refrigerant has several advantages over the R134a refrigerant. This caveat is not limited to the tankless versus tank-style water heating debate. Two tank-style heat pump water heaters also make use of the R744 CO2-based refrigerant. At first glance, it might look like the R134a refrigerant tends to provide a higher COP than R744.
However, the R744 refrigerant has been shown to have higher heat transfer characteristics. This allows the refrigerant to work more efficiently in colder weather when compared to the R134a refrigerant. Hence, in colder ambient weather, the efficiency of R134a-powered tank-style water heaters would drop significantly and might even be less efficient than the R744-powered heat pump water heaters. You can read this article to access the scientific research surrounding this claim. It was found that R134a-powered heat pump water heaters consumed more than twice the amount of energy in Chicago when compared to the energy it consumed in Houston for the same output. You can read more about this study here.
Heating output is a metric used to determine a heating system’s capability to provide the required heat energy needed in a given frame of time to meet all the hot water demands. A like-for-like comparison by looking at heating output numbers between a tankless and a tank-style water heater can be misleading too.
As mentioned earlier, a tank-style water heater would need to consume higher amounts of energy to keep the water stored in a tank constantly hot. A tankless water heater would only need to provide enough heating output to meet peak demand. Hence, a better metric for tankless heat pump water heaters would be the first hour rating. The first hour rating indicates the number of gallons of hot water that a water heater can provide in an hour. Intellihot’s high-strength commercial tankless water heater (Electron iE1) can provide up to 154 gallons of hot water every hour. Unfortunately, the tank-style heat pump water heaters mentioned in the comparison did not provide any information regarding their first hour rating.
Another aspect to note about Intellihot’s tankless heat pump water heater technology is their ability to cascade. The medium-strength commercial tankless heater (iE1) can be wirelessly cascaded with 3 other units over Bluetooth. Hence, the combination of 4 units can provide 360,000 BTUs/hr.
The high-strength commercial tankless water heater (iE6) can be paired with up to 4 iB3 thermal batteries. Doing so will enable the system to store more energy for use whenever there is a hot water demand.
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