Best Heat Pump Water Heaters
Ranked on the three numbers that matter: UEF, first-hour rating, and how cold the room can get.
Heat & Tap earns a commission on qualifying purchases made through the Amazon links on this page, at no extra cost to you. Commission does not decide what we recommend or how we rank it. Full disclosure.
The Rheem ProTerra 50 is the heat pump water heater to start with: 3.88 UEF, a 67-gallon first-hour rating, and a 37 to 145°F ambient operating range that keeps the compressor working in an unheated garage. For the highest published efficiency, the A. O. Smith Voltex AL at 4.02 UEF; for the largest delivery, the Voltex MAX at 83 gallons in the first hour.
Three numbers decide a heat pump water heater, and the third one is the one nobody looks at.
- UEF — how much electricity it uses. The spread here is 3.0 to 4.02, which is a real difference but a smaller one than the gap to a resistance tank at 0.93.
- First-hour rating — whether it keeps up with your household. 67 to 83 gallons across these units.
- Ambient operating range — how cold the room can get before the compressor stops and the expensive backup element takes over. This is the one that decides whether your efficiency is theoretical or actual.
Quick picks
Tap any row to read the full assessment below, or go straight to Amazon from the right-hand column. We earn a commission on qualifying purchases at no extra cost to you.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | Rheem ProTerra 50 gal hybridThe heat pump water heater to start with: a 3.88 UEF, a 67-gallon first-hour rating, and a 37°F lower operating limit that is the widest ambient range in its class — which is the specification that decides whether it works in a cold garage. | Most heat pump installs | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 2 |  A. O. Smith Voltex AL, 66 galThe efficiency leader on this page at 4.02 UEF, in the capacity that suits a five- or six-person household, with a heavy-duty anode rated to protect the tank for 10 years. | Highest published heat pump efficiency | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 3 |  A. O. Smith Voltex MAX, 66 galAn 83-gallon first-hour rating at a 3.84 UEF — the heat pump water heater for a household that runs several showers back to back and still wants the running cost of a heat pump. | Largest first-hour rating | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 4 |  Rheem ProTerra 120 V plug-in, 50 galThe one heat pump water heater that does not need an electrician: it runs on a dedicated 120 V 15 A circuit, which makes it the only realistic efficiency upgrade in a condo or a house with a full panel. | No 240 V circuit available | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 5 |  A. O. Smith ProLine XE, 66 galThe entry point into 66-gallon heat pump capacity: 3.42 UEF and a 79-gallon first-hour rating, with a 6-year anode instead of the Voltex line's 10. | Cheapest route into a large heat pump | Check price on Amazon No live price feed on this site, so we show none. #ad |
The picks in full
Pick 1 — Most heat pump installs
Rheem ProTerra 50 gal hybrid
The heat pump water heater to start with: a 3.88 UEF, a 67-gallon first-hour rating, and a 37°F lower operating limit that is the widest ambient range in its class — which is the specification that decides whether it works in a cold garage.
| Capacity | 50 gallons |
|---|---|
| Efficiency | 3.88 UEF; up to 4.07 UEF advertised on 30 A models |
| First-hour rating | 67 gallons |
| Recovery | 27 gallons per hour |
| Heat pump capacity | 4,200 BTU/h |
| Backup element | 5,000 W |
| Voltage | 208 - 240 V |
| Ambient operating range | 37 - 145°F |
| Cold-climate rating | Meets Northern Climate Specification Tier 4 |
| Leak protection | Integrated detection with factory-fitted auto shutoff; leaks limited to no more than 20 oz |
| Warranty | 10-year limited |
What is good
- A 37°F lower limit means the compressor keeps running in an unheated garage through most of a northern winter
- 3.88 UEF is roughly four times a resistance tank, so the running cost difference is not marginal
- 67-gallon first-hour rating is better than most 50-gallon resistance tanks
- EcoNet control lets you force high-demand mode before guests arrive instead of discovering the limit
What is not
- It is a refrigeration appliance in your house: there is a compressor, a fan and a condensate drain
- Needs roughly 700 cubic feet of air, or louvered doors, in a closet
- It cools and dehumidifies the space it stands in, which is a gift in a Houston garage and a problem in a Minnesota basement
Skip it if: Skip it if the only place it can go is a finished, heated room you occupy. It will steal heat from that room in winter — your furnace then pays for the hot water, and the efficiency you bought disappears.
No live price feed on this site, so we show none. #ad
Specifications above from Rheem ProTerra PROPH50 T2 RH375-30 product page; ABR Wholesalers listing, PROPH50 T2 RH375-30. We have not tested this unit ourselves.
Pick 2 — Highest published heat pump efficiency
A. O. Smith Voltex AL, 66 gal
The efficiency leader on this page at 4.02 UEF, in the capacity that suits a five- or six-person household, with a heavy-duty anode rated to protect the tank for 10 years.
| Capacity | 66 gallons |
|---|---|
| Efficiency | 4.02 UEF |
| Anode | Heavy-duty, rated to protect the tank for 10 years |
| Warranty | 10-year limited |
| Certification | ENERGY STAR certified |
What is good
- 4.02 UEF is the highest figure of any unit in this registry
- 66 gallons removes the recovery anxiety that a 50-gallon heat pump creates in a big household
- The 10-year anode is a real durability claim, not a marketing one
- ENERGY STAR certification keeps it inside most utility rebate lists
What is not
- 66 gallons is a tall, wide cabinet — measure the space before you order
- Sold mainly through wholesale, so availability is slower than big-box
- Published first-hour rating is not listed for the AL model; the Voltex MAX at the same capacity is rated at 83 gallons
Skip it if: Skip it if your install space is a closet. A 66-gallon heat pump needs air volume to work, and starving a heat pump water heater of air is how you end up running on the backup element and paying resistance rates for a premium appliance.
No live price feed on this site, so we show none. #ad
Specifications above from Auer Steel listing, A. O. Smith HPTS-66 Voltex AL; A. O. Smith Voltex AL introduction. We have not tested this unit ourselves.
Pick 3 — Largest first-hour rating
A. O. Smith Voltex MAX, 66 gal
An 83-gallon first-hour rating at a 3.84 UEF — the heat pump water heater for a household that runs several showers back to back and still wants the running cost of a heat pump.
| Capacity | 66 gallons |
|---|---|
| First-hour rating | 83 gallons |
| Efficiency | 3.84 UEF |
| Certification | ENERGY STAR certified |
What is good
- 83 gallons in the first hour beats an 80-gallon resistance tank
- 3.84 UEF is still roughly four times a resistance tank
- 66 gallons of storage plus fast recovery is the combination big households actually need
- ENERGY STAR certified for rebate eligibility
What is not
- Lower UEF than the Voltex AL at the same capacity — you are trading some efficiency for delivery
- Large footprint
- Wholesale distribution
Skip it if: Skip it if two people live in the house. You would be buying 66 gallons and an 83-gallon first-hour rating to serve a demand a 50-gallon unit covers, and paying standby losses on the difference every day for a decade.
No live price feed on this site, so we show none. #ad
Specifications above from First Supply listing, A. O. Smith HPTA-66 Voltex MAX. We have not tested this unit ourselves.
Pick 4 — No 240 V circuit available
Rheem ProTerra 120 V plug-in, 50 gal
The one heat pump water heater that does not need an electrician: it runs on a dedicated 120 V 15 A circuit, which makes it the only realistic efficiency upgrade in a condo or a house with a full panel.
| Capacity | 50 gallons |
|---|---|
| Voltage | 120 V |
| Power | 1.8 kW |
| Circuit | Dedicated 120 V 15 A |
| Efficiency | 3.0 UEF on a dedicated circuit; up to 3.5 UEF on the shared-circuit model |
| Ambient operating range | 37 - 145°F |
| Cold-climate rating | Designed to meet NEEA Northern Climate Specification Tier 2 |
| Utility programs | Built-in EcoPort CTA-2045 port |
What is good
- A standard 120 V circuit removes the panel upgrade that kills most heat pump retrofits
- Still roughly three times as efficient as a resistance tank
- CTA-2045 port makes it eligible for utility demand-response payments where those exist
- Same 37°F lower operating limit as the 240 V models
What is not
- 1.8 kW means slow recovery — this is a tank you let work overnight, not one you push
- No big resistance element to bail you out during a surge in demand
- A dedicated circuit is still a circuit: a shared-outlet install is a different model number
Skip it if: Skip it if your household regularly empties the tank — a big family, or two showers plus a dishwasher back to back. With 1.8 kW of input and no large backup element, recovery is the whole constraint.
No live price feed on this site, so we show none. #ad
Specifications above from Rheem plug-in heat pump specification sheet (PDF); Ferguson listing, ProTerra 50 gal 120 V plug-in. We have not tested this unit ourselves.
Pick 5 — Cheapest route into a large heat pump
A. O. Smith ProLine XE, 66 gal
The entry point into 66-gallon heat pump capacity: 3.42 UEF and a 79-gallon first-hour rating, with a 6-year anode instead of the Voltex line's 10.
| Capacity | 66 gallons |
|---|---|
| First-hour rating | 79 gallons |
| Efficiency | 3.42 UEF |
| Anode | Heavy-duty, rated to protect the tank for 6 years |
| Certification | ENERGY STAR certified |
What is good
- 79-gallon first-hour rating for the lowest price of the three 66-gallon units here
- 3.42 UEF is still a step change from any resistance tank
- ENERGY STAR certified
- Same large capacity as the Voltex models
What is not
- The 6-year anode rating is the clearest difference from the Voltex line, and anodes are what tanks die from
- Lowest UEF of the heat pump units listed here
- Wholesale distribution
Skip it if: Skip it if your water is hard or softened. Anode life is what decides when the tank leaks, and in aggressive water the 6-year anode rating is the figure that will come back to bite you — pay for the Voltex AL's 10-year anode instead.
No live price feed on this site, so we show none. #ad
Specifications above from First Supply listing, A. O. Smith FPTU-66 ProLine XE Voltex. We have not tested this unit ourselves.
Side by side
| Unit | Capacity | UEF | First-hour rating | Ambient range | Warranty |
|---|---|---|---|---|---|
| Rheem ProTerra 50 | 50 gal | 3.88 (up to 4.07 on 30 A models) | 67 gal | 37 to 145°F | 10-year limited |
| A. O. Smith Voltex AL | 66 gal | 4.02 | Not published for the AL | Not published on the listings we read | 10-year limited, 10-year anode |
| A. O. Smith Voltex MAX | 66 gal | 3.84 | 83 gal | Not published on the listings we read | Per model documentation |
| A. O. Smith ProLine XE | 66 gal | 3.42 | 79 gal | Not published on the listings we read | 6-year anode |
| Rheem ProTerra 120 V plug-in | 50 gal | 3.0 dedicated; up to 3.5 shared circuit | Not published | 37 to 145°F | Per model documentation |
Why the ProTerra 50 leads
Not because it has the highest UEF — the Voltex AL does. It leads because its published ambient operating range is the most useful specification in this category and Rheem states it prominently: 37 to 145°F, meeting Northern Climate Specification Tier 4.
A 4.02 UEF unit that falls back to resistance heating every time the garage drops to 45°F delivers worse real-world efficiency than a 3.88 UEF unit whose compressor keeps running at 38°F. In a northern garage, the ambient limit matters more than the nameplate efficiency.
The ProTerra also carries integrated leak detection with a factory-fitted automatic shutoff valve that limits a leak to no more than 20 ounces, which is worth real money on a unit that also makes condensate.
Choosing a capacity
| Household | Capacity | Example |
|---|---|---|
| 1 to 3 people | 50 gal | Rheem ProTerra 50, 67 gal first hour |
| 4 people | 50 gal | Rheem ProTerra 50 |
| 5 people | 66 gal | A. O. Smith Voltex MAX, 83 gal first hour |
| 6 or more | 66 to 80 gal | Voltex MAX, or a larger unit |
Heat pump units size more favorably than resistance tanks because the first-hour ratings are better. A 50-gallon heat pump at 67 gallons first hour covers a household that would need a 65-gallon resistance tank. Sizing.
The 120 volt option
The Rheem ProTerra 120 V plug-in exists for one specific and very common situation: the panel has no room, or the unit is in a condo where new circuits are a governance problem. It runs on a dedicated 120 V 15 A circuit at 1.8 kW, still roughly three times as efficient as a resistance tank.
What you give up is recovery. 1.8 kW is slow, and there is no large resistance element to bail you out during a surge. It suits a household with moderate, predictable demand. 120 V plug-in models.
What goes in with it
A water heater is a system, not a box. These are the parts that go in with it, and the ones people discover they need halfway through the job.
- Drain pan
A heat pump water heater makes condensate continuously, so this one is not optional.
- Leak detector
A condensate line that blocks will overflow long before you notice it.
- Expansion tank
Same closed-system rule as any other storage tank.
How we chose
Ambient operating range first, because a heat pump that falls back to resistance is not a heat pump; then first-hour rating; then UEF; then warranty and anode terms, since the anode is what decides when the tank fails. We read owner reviews for repeat complaints — fan noise and condensate drainage are the two that recur. We have not tested these units. How we pick.