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Image courtesy of the Advanced Water Heating Initiative

Consumer Technology

All I Want For Christmas Is A New Voltex AL Heat Pump Water Heater

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Heat pump water heaters (HPWHs) are a key technology for a zero-emissions 21st century. They are 2–4 times more efficient than fossil gas or electric resistance water heaters, emit little if any CO2 (depending on your electricity mix), and cost around $100 a year to operate. And, if you’ve got lots of family members, housemates, or guests taking back-to-back showers, they heat water faster than electric resistance water heaters.

But unlike heat pumps for home heating, which are picking up more market share and recently surpassed gas furnace sales, HPWHs are still not on enough people’s radar screens and account for about 1% of water heaters sold nationally.

Image courtesy of the Advanced Water Heating Initiative

I spend my working hours thinking about HPWHs with the nonprofit New Buildings Institute, and one of my goals as a proud scribe for CleanTechnica is to bring reviews of HPWHs to our readers the way we so often read about the latest reviews of new electric vehicles. In September, I reviewed Rheem’s 120-Volt HPWH. My goal is to write reviews and share information about all available HPWH brands to get the word out about this great technology.

Today, I’ll be writing about A. O. Smith and its new Voltex AL HPWH. A. O. Smith is one of the Big Three in the world of heat pump water heating. It shares that top tier with Rheem and Bradford White. There are a couple of big manufacturers starting to get in the HPWH game as well. These include Mitsubishi, LG, and GE. There are also smaller companies that make split system HPWH (which means the condenser is separated from the tank). These include Nyle and Eco2 Systems.

The Voltex AL is the fourth version of A. O. Smith’s HPWH product. A. O. Smith started working on HPWHs back in 2007 and the fourth generation of this product takes the learnings and recommendations from 15 years of HPWH development and tens of thousands of units sold to create a pretty great appliance crucial to any home’s efforts to save money and decarbonize.

Efficiency and Cost Savings

There is a lot to be excited about with the new Voltex AL. First off, it has incredible efficiency. The Voltex is one of the most efficient water heaters on the market, with a Uniform Energy Factor (UEF) of up to 4.02 (that means for every unit of energy you put in, you get four units of heat out). To put that in context, gas water heaters are typically 0.60, instant gas water heaters are 0.81, and electric water heaters are 0.92.

That efficiency translates into incredible savings. ENERGY STAR says a family of four will save $470/year in operational savings from a HPWH and the DOE Energy Guide says the average user will save $200/year compared to gas.

This chart shows estimated installation and savings for a heat pump water heater with new IRA tax credits.

With the Inflation Reduction Act (IRA) 30% tax credit factored in, you’re looking at about a two-year payback if you switch out your electric resistance water heater. What other clean energy investment has a two-year payback? For comparison, solar panels often have a 10+ year payback.

Remember efficiency doesn’t have to mean “less” hot water. The 50-gallon A. O. Smith Voltex AL has a first-hour rating of 66 gallons (the amount of hot water you can get from a fully heated tank), which is greater than a similarly sized standard electric water heater.


HPWHs sound like a refrigerator. They make a little humming noise. Some of the early versions of HPWHs made more noise, up to 55 decibels. This new version of the Voltex is rated at 45 dBA, which is the same noise range as a quiet dishwasher. That’s pretty darn quiet — you can put this machine anywhere, even a utility closet in a living space, and not notice the sound (a wall or door will typically reduce sound 10–20 dBA further so that you’re unlikely to hear it, unless you are standing right next to it).

Need less air space

HPWHs need adequate air supply to work as they pull heat from air and transfer it to water. Until recently, the standard required room air space was 700 cubic feet of air space, which is about the size of a small home office with a low ceiling. The recent Northwest Energy Efficiency Alliance’s shrinking room study tested the efficiency of an A. O. Smith Voltex HPWH in gradually smaller amounts of air. This study found that the Voltex still worked efficiently down to 450 cubic feet of air space, so A. O. Smith reduced the recommended air space accordingly. This means there are more options for installation and if you have an even smaller utility closet, like my family does, you can also add a vent or louvered door to give the water heater the air it needs.

Plumber’s dream

Whether you’re installing the heat pump water heater yourself or relying on the growing ranks of plumbers that are getting ahead of the competition and specializing in this type of water heater installation (A. O. Smith has a plumber finder on its website), the new Voltex makes installation easier than it’s ever been.

Earlier versions of the water heater had plumbing connections on the side, but A. O. Smith received resounding feedback from plumbers indicating a preference for top water connections when replacing a standard electric water heater. The Voltex AL gives you the option to do both, they added water connections on the top and kept the ones on the side as well, rotating them around to the front for easier access.

The Voltex AL is also zero clearance on the back and sides and can go right up next to the wall similar to an electric water heater.

Smart water heating

The Voltex AL is also a smart water heater. It incorporates leak detection into the water heater and has an optional water shutoff valve. If the water heater senses a leak, it can automatically shut off water to the water heater.

The water heater can also help you use electricity when it’s cheaper to do so. The Voltex has an accompanying app where a user can select the utility rate plan and have the HPWH mimic an electric vehicle charger, using energy when it’s cheaper to do so. Water heaters store enough water (50+ gallons) to last an average family a day, so this ability to delay use of energy won’t leave you without hot water.

All in all, I’m excited about the Voltex AL. This fourth-generation HPWH improves what is already an incredible product in so many ways. The Voltex AL was launched in the Northwest in the summer of 2022 and is now available nationwide through professional plumbing contractors (find them here).

Buy a heat pump water heater for that special someone this holiday season and start saving money while decarbonizing your water heating today.


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Written By

Joe lives in Portland, Oregon, and works for the nonprofit New Buildings Institute, which promotes electric and decarbonized buildings. He also volunteers with Electrify Now because he believes that electrifying everything, from transportation to homes, is the quickest path to an equitable, clean energy future. And of course, Joe and his family live in an all-electric home and drive an EV.


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