Split Heat Pump vs Hybrid Heat Pump for Water Heaters
When selecting a heat pump water heater for your home, you have two options. Split systems place the heat pump outside with the storage tank inside. Hybrid models put everything together in one unit. Which one fits your home depends on your available space, climate, and how much hot water you need.
Need help figuring out which water heater setup fits your home? Use our XPERT™ Residential Water Heater Selector to get a personalized recommendation.
Heat Pump Water Heating Technology
Heat pump water heaters move heat from the air into your water instead of creating heat from scratch. A fan pulls air across coils filled with cold refrigerant. The refrigerant soaks up warmth from that air, then a compressor squeezes the refrigerant to make it even hotter. Hot refrigerant then flows through coils wrapped around your water tank, transferring its heat to the water inside. Split heat pumps like the Voltex® X use CO2 refrigerant, which is what allows them to operate in much colder conditions than hybrid models, with some working down to -25°F and up to 109°F.
Your home's hot water demand and energy costs are good starting points when comparing the efficiency of electric water heaters vs. split heat pumps.
Hybrid Heat Pump Water Heaters
Hybrid heat pump water heaters put the compressor, fan, coils, and controls on top of the storage tank. Everything sits in one unit that plugs into a single power source. A. O. Smith's ProLine® XE Voltex® is a great example of this style of heat pump water heater.
Single-Unit Setup
The heat pump equipment mounts on top of an insulated tank, making the whole unit taller than a standard electric water heater. You get one electrical hookup, no outdoor gear, no refrigerant lines running through your walls, and no need to juggle multiple pieces of equipment during installation.
Where They Fit and What They Need
The units pull in room air to grab heat from it, so they need the correct setup to work well:
- Enough Air Space: The room where the unit is installed needs at least 450 cubic feet of air volume so the heat pump isn't just recirculating air it has already cooled down.
- Air Movement: The unit pulls in air, extracts the heat, and blows cooler air back into the space.
- How Seasons Affect Performance: In summer, this actually helps cool the room where it's installed. In winter, the unit works harder when pulling heat from cold basement or garage air.
- Backup System: Electric elements kick in when the air gets too cold for the heat pump to handle on its own.
Not sure if a heat pump water heater is right for your home? Learn more about the pros and cons of heat pump water heaters before deciding which setup makes the most sense for you.
Water Heater Selector Quiz
Need Help From A Pro?
A. O. Smith water heaters are professionally installed by local independent contractors.
Split System Heat Pump Water Heaters
The Voltex® X puts the heat pump outside and the storage tank inside. The outdoor unit has the compressor, fan, and heat exchange equipment. The indoor tank holds heated water.
Two-Part Configuration
Split systems completely separate the heat pump machinery from the tank. Outdoor units mount outside your home, and we offer several mounting solutions, including ground pads, roof installs, and wall mounts. Water lines run from the outdoor unit through your wall to the indoor storage tanks.
Indoor tanks don't need as much ceiling height as hybrid models since all the bulky heat pump equipment sits outside. This means tanks can fit into mechanical closets, spaces under stairs, or other spots where a tall hybrid unit won't fit. Tank options are available in 50, 66, and 80-gallon capacities across five configurations, making it easier to find a size that fits your space.
Setting Up the System
You need installers with plumbing experience. Here's what they do:
- Outdoor Unit: Mount it on a pad with drainage.
- Water Lines: Run up to 66 feet of ½-inch water line through your exterior walls and seal the holes.
- Electrical: The outdoor heat pump unit requires a 208/240 VAC, 60Hz, single-phase, 20-amp power supply, and the indoor storage tank requires a 120 VAC, 60Hz, single-phase, 15-amp shared circuit.
- Controls: An RS-485 communications cable connects the outdoor unit with the tank and controller inside, allowing the heat pump and the storage tank to communicate.
The outdoor unit needs clearance on all sides for airflow and future servicing. Indoor tanks connect to your home's existing hot water pipes just like any other water heater.
Safety and Smart Features
The indoor tank includes a mixing valve, which is required because the CO2 refrigerant heats water to around 140°F. The mixing valve brings the output temperature down to a safe level before it reaches your fixtures. The system has a built-in freeze defense through heat pump circulation. An optional Anti-Freeze Valve Kit is also available for additional protection during power outages. For added peace of mind, iCOMM™ connectivity allows for remote monitoring, and built-in leak detection keeps tabs on the system around the clock.
The Voltex® X also offers three operating modes: Heat Pump for maximum energy efficiency, Guest for maximum hot water delivery over up to seven days, and Vacation to reduce energy use while you're away.
Cold Weather Performance
Split systems grab heat from outside air regardless of the weather. The outdoor unit continues to operate as temperatures drop and automatically runs defrost cycles when ice builds up on the coils. The CO2 refrigerant has low global warming potential and enables performance in extreme cold, down to -25°F and up to 109°F.
In cold climates, this setup doesn't pull heat from your mechanical room the way hybrid models do, so it won't affect your home's heating costs in winter.
Water Heater Selector Quiz
Need Help From A Pro?
A. O. Smith water heaters are professionally installed by local independent contractors.
Installation and Operating Costs
The equipment you pick, the work to install it, and how it runs over its lifetime all add up differently depending on which system you choose.
Who Can Install It and What's Involved
Hybrid heat pump water heaters need a plumber familiar with heat pump installations. The work includes running water supply and distribution pipes, and routing condensate drainage.
Split systems also need a licensed plumber, but the installation story is simpler in one important way. Since the system uses a water line split rather than a refrigerant split, the refrigerant comes pre-charged and sealed in the outdoor unit. Installers never need to touch or handle it, which means no HVAC technician or special refrigeration license is required. The work involves mounting the outdoor unit, running water lines through the exterior wall, and connecting the indoor tank.
Operating Costs
The Voltex® X can save homeowners an average of $600 per year compared to standard electric water heaters. Both systems qualify for federal tax credits and rebates, which can help offset the higher upfront cost. Visit the A. O. Smith rebate center to explore available incentives in your area.
Energy Performance
Both systems are significantly more efficient than standard electric resistance water heaters because they move heat rather than create it. Hybrid heat pump models use up to 70% less electricity than standard electric water heaters. The Voltex® X reaches a UEF of up to 3.80, reducing water heating costs by up to 76% compared to standard electric water heaters.
The Voltex® X is also ENERGY STAR® certified, qualifying it for many state and local utility rebates. An A. O. Smith certified installer can walk you through the current efficiency details for both systems.
Picking a Heat Pump Setup for Your Home
Which configuration makes sense depends on your home's specific situation. Hybrid heat pump water heaters are a good fit when you have adequate space for airflow of at least 450 cubic feet, your hot water needs align with what a single unit can deliver, and you want a straightforward installation process.
Split systems are worth considering when your water heater is in a closet or tight space where a standard heat pump won't fit, when you live in a cold climate where temperatures regularly drop below 37°F, or when you want zero indoor noise since all the mechanical components are outside. The outdoor unit operates at 40 dBA, comparable to the noise level in a quiet library.
A. O. Smith Heat Pump Solutions
A. O. Smith has been delivering innovative water heating solutions for over 80 years. Whether a ProLine® XE Voltex® hybrid heat pump fits your space or the Voltex® X better suits your climate and installation needs, A. O. Smith has options built for reliable, energy-efficient performance. Both come backed by a 10-year limited warranty. Use our XPERT™ Residential Water Heater Selector to find the right fit, or connect with a local installer who can assess your home and walk you through your options.
Frequently Asked Questions
Neither system requires an HVAC technician. Hybrid heat pump water heaters need a plumber familiar with heat pump installations, including condensate drainage and making sure the space has at least 450 cubic feet of airflow. Split systems need a licensed plumber for water line connections and outdoor unit mounting. Because the refrigerant comes pre-charged and sealed in the outdoor unit, no refrigeration license is required.
Split system heat pumps extract heat from outdoor air, so they operate independently of the temperature inside your home. Hybrid models draw warmth from the air in the space where they're installed, which means they work harder in winter when that indoor air is cooler.
The difference comes down to where everything sits. The Voltex® X has the heat pump outside and the tank inside. Hybrid models put everything in one unit. Split systems need less ceiling height and have no indoor airflow requirements, while hybrid models need at least 450 cubic feet of air space and condensate drainage, but keep all equipment contained indoors.