Split heat pump water heaters (HPWH), where the compressor and tank are separated, are having a moment. Several new products have come to market this year, and more are on the way. To add to this excitement, A. O. Smith, one of the “big three” manufacturers in US water heating, just released a new split HPWH called the Voltex X, partnering with Panasonic on the product. I sat down with A. O. Smith in our podcast Heat Pumps and Cardigans to talk about the Voltex X, to see some of its potential benefits and challenges, and to discuss how it is rolling out across the country. How the Voltex X Came to Be While most buildings can use a unitary HPWH (where the tank and compressor are joined together), some abodes like apartments and mobile homes don’t have the air space or tank space required for a HPWH and will likely need other solutions. AO Smith developed the Voltex X because they saw they had a gap in their product lineup and they wanted to create a HPWH option for those homes. But rather than make the outdoor heat pump themselves, A. O. Smith decided to partner with Panasonic, as they have been working hard on heat pump technology for decades, especially those that use CO2 as a refrigerant. A. O. Smith figured that if they married Panasonic’s heat pump with their own tank-making abilities, they could produce a new and compelling split HPWH. Hydronic over refrigerant lines Split HPWHs come in two flavors, they either run water (aka hydronic) or refrigerant lines between the indoor and outdoor units. A. O. Smith decided to use water lines because they didn’t want plumbers to have to work with refrigerant (we should say that currently the one manufacturer that uses refrigerant uses pre-charged lines so that plumbers don’t have to deal with refrigerant if they don’t want to with that system either). With the Voltex X, plumbers will just have to run water lines from the tank to the outdoor unit where the refrigerant is contained within a sealed system. Features Let’s look at some features of the Voltex X. Small tank size options — The Voltex X has five tank size options. The smallest is what is called a “low-boy” tank. It is short (36 inches) and fat (26 inches) and intended to fit into small spaces that can’t otherwise accommodate large water heater. The Voltex X’s low boy tank is 7 inches smaller than the next smallest HPWH tank — (SanCO2’s) and almost half the size of a typical unitary HPWH. The other tank sizes range from 48–60 inches in height. The five different tank types currently available with the Voltex X. CO2 refrigerant — The Voltex X becomes the second residential HPWH on the American market to use CO2 as a refrigerant. CO2 is beneficial because: 1) It works in really cold temperatures. In A. O. Smith’s case that means down to -25 degrees Fahrenheit. 2) CO2 heats water really quickly. A. O. Smith’s fifty gallon tanks have a seventy gallon first hour rating which is high. 3) It doesn’t need an electric resistance backup. Because of #1 and #2, systems that use CO2 don’t need or have an electric resistance backup. This makes them even more efficient because some studies have found that 30% of energy used in a HPWH is used in electric resistance mode which is much less efficient than heat pump mode. Mixing valves, water lines and one to one replacements — A couple other interesting things about the Voltex X are that: It comes with a mixing valve — which means you can store water hotter and mix in cold water. Storing water hotter means more hot water to use in a home. Water lines between the outdoor unit and water tank can max out at lengths of 66 feet. One to one replacements — the residential version of the Voltex X is really meant as a 1 to 1 replacement. That means one Voltex X would serve one apartment or home. The upcoming commercial version of the product can be stacked to serve many apartments in a building. Potential Challenges Now let’s look at a couple potential challenges with the Voltex X. Water lines in cold weather — Freeze protection is always a concern when you have water lines outdoors in cold climates. The Voltex X handles freeze protection through an active (circulating warm water through the pipes during cold weather) and passive system (valve that opens up to drip and keep water moving when the power is out). Still, I have heard from industry folks that freeze protection is always a potential concern even when you have a robust freeze protection system like the Voltex X does. At AWHI, we’ll be testing the Voltex X’s freeze protection in a couple of field studies we’re conducting so will have more to report back on. Cost — Split HPWHs are considered more complicated in many ways than the unitary systems and traditionally have cost more for both equipment and installation. I’ve surveyed a couple installers about general pricing of the Voltex X and am hearing between $4,000–$4,500. This is below or comparative to other split HPWHs on the market but above unitary HPWH costs which typically range from $1,600–$3,500. But, for the households that can’t add a unitary HPWH to space challenges, it’s great to have another product to choose from. Water tank requires electricity — I’ve heard from one installer that the fact that the water tank requires a 120V electrical connection is an annoyance. Putting in a Voltex X means you’ll need to run electricity to both the outdoor unit (240V, 20 amp circuit) and indoor water tank (120V, 15 amp) which is more electrical connections than you need with unitary HPWHs. Coming to market A. O. Smith is the first major manufacturer to bring a split HPWH to market which increases split HPWH access and availability of split HPWHs in the US. The company said the products are available at distributors across the country. The manufacturer has created some excellent training videos for the Voltex X which you should check out here to do a deeper dive on the product. The residential Voltex X has 4.5 kW of power. A. O. Smith is launching its 6 kW commercial unit soon as well which can be stacked in up to 30+ units, forming a much bigger Central HPWH that can provide hot water for large multi-family buildings. We look forward to seeing how this and other split HPWHs change the US market and offer more options for those looking to heat their water cleanly with a heat pump. Watch our full Heat Pumps and Cardigans podcast with A. O. Smith here Or listen on Spotify This content is provided for informational and educational purposes only. The Advanced Water Heating Initiative (AWHI) does not receive payment, free products, or other compensation for manufacturer spotlights, interviews, or articles, and does not endorse or recommend specific products or brands. AWHI’s role is to educate the market on developments in heat pump water heater technology in support of informed decision-making and market transformation. Read more about AWHI’s content policy here.
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