Best Heat Pump (Hybrid) Water Heaters (2026)

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Quick answer from a licensed plumber: For most homes replacing a 50-gallon electric tank, buy the Rinnai REHP50: 3.75 UEF, a 73-gallon first-hour rating and 10 years on tank and parts, sold on Amazon by a Rinnai authorized e-tailer. Step up to the REHP65 if a 50-gallon tank runs short. Any of these needs a 30-amp 240-volt circuit and a condensate drain. The Rinnai units also need at least 700 cubic feet of room air or a louvered door or duct kit; Senville gives no small-room rule, so check with Senville before putting its unit in a closet.

Our pick for most homes: the Rinnai REHP50 50-gallon heat pump water heater. Check the Rinnai REHP50 on Amazon

A heat pump water heater, sold as a hybrid, is an electric tank with a small heat pump on top. It pulls heat out of the room air into the water and keeps standard elements as backup. For efficiency the number to compare is UEF, and all four units here rate 3.75 or better; for hot water supply it is the first-hour rating. The limits are physical: the room has to supply enough air, the unit needs a condensate drain, and it cools the space it sits in. These are the ones we would buy on Amazon, checked against the makers’ manuals and spec sheets.

Heat Pump Water Heaters Compared

Model	Gallons (nominal / rated)	UEF	First-hour rating (gal)	ENERGY STAR kWh per year	Height × width	Warranty
Rinnai REHP50	50 / 46	3.75	73	844	66.4 × 21.7 in	10 yr tank and parts
Rinnai REHP65	65 / 61	3.90	80	1,240	65.5 × 25.6 in	10 yr tank and parts
Rinnai REHP80	80 / 74	4.00	91	1,225	74.2 × 25.6 in	10 yr tank and parts
Senville SENWH-HP50US	50 / 47	3.75	69	855	66.4 × 21.7 in	7 yr parts, 10 yr compressor

Sizes, UEF and first-hour ratings come from Rinnai’s REHP brochure and spec sheet and Senville’s product page and manual; yearly kWh comes from the ENERGY STAR listings. ENERGY STAR rates the 50-gallon units on its medium-usage test and the 65 and 80 on its high-usage test, so compare kWh within a size, not across sizes. Heights and widths in the table are from Rinnai’s brochure and spec sheet; Rinnai’s product pages list the REHP50 at 66.8 × 22.0 in, the REHP65 at 65.0 × 25.7 in and the REHP80 at 74.6 × 25.7 in, and the ducting drawing in Rinnai’s manual shows the 65 and 80 at 25.8 in across, so measure against the larger figure. Each linked unit was listed in stock on Amazon when we checked on September 29, 2026. The Rinnai units are sold by eFaucets, a Rinnai authorized e-tailer; the Senville is sold by Senville. Rheem, A.O. Smith and Bradford White also make heat pump water heaters, but none was in stock on Amazon when we checked, so they are not linked here; ENERGY STAR suggests asking local installers and retailers what they carry.

Best Overall

Rinnai REHP50 50-Gallon Heat Pump Water Heater

50 gal nominal, 46 gal rated · UEF 3.75 · 73-gal first-hour rating · 208/240 V, 30 A breaker · 4,500 W backup elements · heat pump runs in 37–107°F room air (108°F in the manual) · 3/4-inch MNPT water connections · 66.4–66.8 in tall × 21.7–22.0 in wide, 212–218 lb (Rinnai documents differ) · 10-yr tank and parts, 1-yr labor

The REHP50 is Rinnai’s 50-gallon heat pump water heater, and it is the one to put in place of a standard 50-gallon electric tank. Rinnai lists a 3.75 UEF and a 73-gallon first-hour rating, the highest first-hour figure of the 50-gallon units on this page. It runs on a 208/240-volt, 30-amp supply and keeps 4,500-watt elements as backup. Per the manual, the heat pump runs when the room air is between 37 and 108°F (Rinnai’s spec sheet says 107°F); outside that range the elements carry the load. There are five modes. Economy is the default, and Rinnai describes it as heat pump first, with the elements only when demand gets very high.

The warranty is the longest on this page: 10 years on the tank and all other parts, plus 1 year of reasonable labor. Read the conditions, though. Rinnai’s manual limits coverage to a “qualified product installation” by an installer licensed where your state requires one, makes coverage conditional on ongoing maintenance by a professional contractor (licensed where required) recorded in Rinnai’s service record, counts a missing drain pan as improper installation, and voids the warranty on units bought from an unauthorized dealer. The Amazon listing is sold by a seller named eFaucets, and efaucets.com is on Rinnai’s published list of authorized e-tailers allowed to sell on Amazon. Rinnai also needs proof of purchase (a dated receipt, or registering within 90 days), so check that the order page says sold by eFaucets before you buy, keep the Amazon invoice, and register the unit with Rinnai. One conflict to note: Rinnai’s brochure and spec sheet list the unit at 66.4 inches and 218 lb, and its product page says 66.8 inches, 22.0 inches wide and 212 lb. Plan around 66.8 inches tall and 218 lb.

10 years on tank and parts plus 1 year of labor, per Rinnai’s manual
Highest first-hour rating of the 50-gallon units here: 73 gallons
Amazon seller eFaucets is on Rinnai’s authorized e-tailer list
Rinnai’s minimum clearances are 0 inches behind and 6 and 2 inches at the sides (20 inches recommended on top)

Sold by eFaucets, a third-party seller, not by Amazon or Rinnai
Warranty needs a licensed installer where your state requires one, plus a drain pan
Rooms under 700 cubic feet need a louvered door or ducting, per Rinnai
The CTA-2045 demand-response module is not supplied

Verdict: The pick for most houses replacing a 50-gallon electric tank, as long as a licensed plumber installs it so the warranty holds.

Check the Rinnai REHP50 on Amazon

Best for Bigger Households

Rinnai REHP65 and REHP80 Heat Pump Water Heaters

REHP65: 65 gal nominal, 61 gal rated · UEF 3.90 · 80-gal first-hour rating · 65.0–65.5 in tall × 25.6–25.8 in wide, 250–271 lb · REHP80: 80 gal nominal, 74 gal rated · UEF 4.00 · 91-gal first-hour rating · 74.2–74.6 in tall × 25.6–25.8 in wide, 270–290 lb (Rinnai documents differ) · both 208/240 V, 30 A breaker · 10-yr tank and parts, 1-yr labor

If a 50-gallon tank already runs short in your house, the REHP65 is the step up. Rinnai lists an 80-gallon first-hour rating and a 3.90 UEF. It is slightly shorter than the REHP50, at most 65.5 inches against up to 66.8, but it is about 25.6 to 25.8 inches across instead of about 22, depending on the Rinnai document. Measure the closet width and the door you have to carry it through, not only the ceiling height. ENERGY STAR’s listing shows Wi-Fi and CTA-2045 for the REHP65, but none of the Rinnai documents we read mentions Wi-Fi, and Rinnai’s manual shows the CTA-2045 module as not supplied. Confirm with Rinnai before buying it for app control.

The REHP80 is the same design at 80 gallons. Rinnai lists a 91-gallon first-hour rating and a 4.00 UEF, the best efficiency on this page, but it is tall: 74.2 inches in Rinnai’s brochure and spec sheet and 74.6 inches on Rinnai’s product page, so plan for 74.6. The brochure and spec sheet list 290 lb empty and the product page 270 lb, so plan for 290. The Amazon listings for these two swap their UEF figures in the bullet points; Rinnai’s brochure and the ENERGY STAR listings both give 3.90 for the 65 and 4.00 for the 80. Both are sold by eFaucets, so the warranty terms and the authorized-seller point are the same as for the REHP50.

REHP65 gives an 80-gallon first hour in a unit shorter than the REHP50
REHP80 has the highest efficiency here: 4.00 UEF, per Rinnai and ENERGY STAR
Same 30-amp supply and 10-year tank and parts warranty as the REHP50
Rinnai’s brochure lists the same 4,500 W backup elements and 27.5 GPH recovery for all three sizes

About 25.6 to 25.8 inches across; may not fit a closet built for a 50-gallon tank
REHP80 stands up to 74.6 inches tall, per Rinnai’s product page
Sold by eFaucets, a third-party seller, not by Amazon or Rinnai
Amazon bullet points swap the 65 and 80 UEF figures

Verdict: The pick when a 50-gallon tank already runs short. Take the REHP65 unless you need the REHP80’s 91-gallon first hour and have the height for it.

Not linked: Rinnai REHP65 — on 10/3/2026 the Amazon listing was sold by a third-party seller, not by Amazon or the maker. We re-check listings every week.

Not linked: Rinnai REHP80 — on 10/3/2026 the Amazon listing offered only used units. We re-check listings every week.

Best Sold by the Maker

Senville SENWH-HP50US 50-Gallon Heat Pump Water Heater

50 gal nominal, 47 gal rated (manual) · UEF 3.75 · 69-gal first-hour rating · 240 V (208–240 V range) · 26.8 A minimum circuit at 240 V, 30 A maximum fuse, 10 AWG · 4,500 W elements · heat pump runs in 37–109°F room air · 49.5 dBA · 66.4 in × 21.7 in, 218 lb · 7-yr parts, 10-yr compressor

On Amazon the SENWH-HP50US is sold by Senville itself. On size it is a close match for the REHP50: Senville’s product page lists 66.4 by 21.7 inches (its manual’s spec sheet says 66.8 by 21.9), 218 lb and a 3.75 UEF. The first-hour rating is lower, 69 gallons against Rinnai’s 73. Senville lists a 49.5 dBA sound level (ENERGY STAR lists 49 dBA for all four units here), a heat pump range of 37 to 109°F, a 26.8-amp minimum circuit at 240 volts with a 30-amp maximum fuse and 10 AWG wire, and five modes. ENERGY STAR lists it with Wi-Fi and a built-in CTA-2045 port.

The trade-off is the warranty. Senville’s product page lists 7 years on parts and 10 on the compressor and does not state a separate tank term, where Rinnai covers the tank and parts for 10 years. Senville’s manual also says the warranty is void if the installer or owner does not follow the manual. Its product page and manual disagree on rated capacity: 45 gallons on the page, 47 in the manual’s spec sheet and on the ENERGY STAR listing.

Sold on Amazon by Senville, the maker
About the same size as the Rinnai REHP50: roughly 66 to 67 inches tall and 22 inches across
Wi-Fi setup through the NetHome Plus app is covered in Senville’s manual
ENERGY STAR lists Wi-Fi and a built-in CTA-2045 port

7-year parts warranty against Rinnai’s 10, and no tank term on the product page
Lower first-hour rating than the REHP50: 69 gallons against 73
Senville’s page (45 gallons) and manual (47 gallons) disagree on rated capacity
No closet or louvered-door rule in Senville’s manual, which asks for 200 cubic meters of free space

Verdict: The pick if you want to buy from the maker and want Wi-Fi control. For the same space, the Rinnai REHP50 carries the longer warranty.

Check the Senville SENWH-HP50US on Amazon

I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.

Before You Buy

Check the room air. Rinnai’s current manual says a room over 700 cubic feet of free space, not counting what is stored in it, needs no extra ventilation. A room of 85 to 700 cubic feet needs a fully or double louvered door, with upper and lower grilles totaling 250 square inches of net free area and set 5 feet apart. A space under 85 cubic feet needs Rinnai’s duct kit. With the duct kit, Rinnai’s drawing calls for 88.4 to 97.5 inches of headroom, depending on the size. ENERGY STAR is more cautious: 1,000 cubic feet, in a space that stays 40 to 90°F year-round. Rinnai adds that if the room drops more than 15°F while the unit heats, there is not enough air. For a laundry room or closet under 450 cubic feet, Rinnai asks for a louvered door with the louver level with the unit’s air exhaust, the exhaust within 12 inches of the door, and 24 square inches of gap under the door. Rinnai’s rules overlap and do not fully agree: that closet rule lists no minimum room size, the room table says a space under 85 cubic feet must be ducted, and the ducting section says any unvented space under 450 cubic feet must be ducted. Go by the stricter reading: under 85 cubic feet, duct it; from 85 to 450 cubic feet, meet both door rules (the 250 square inches of grilles 5 feet apart, and the louver at exhaust height within 12 inches plus the 24-square-inch gap) or duct it; and have your installer confirm the layout with Rinnai before you buy. Senville’s manual has no closet or louvered-door rule. It says to allow 200 cubic meters of free space around the unit (about 7,000 cubic feet, our arithmetic) and warns that a confined space raises power use, so plan the Senville for a large basement or garage, or get Senville’s written guidance first.
Check the circuit. At 240 volts all four call for a 30-amp breaker and 10 AWG copper (Senville lists a 25-amp maximum fuse at 208 volts). Rinnai’s manual says a qualified electrician must set up a separate branch circuit to the National Electrical Code. If the old electric tank is on its own 30-amp double-pole breaker with 10-gauge copper, the circuit may carry over, but have an electrician confirm it; if it is smaller, have it upgraded before the swap. Replacing a gas water heater means there is no circuit to reuse, so an electrician has to run a new one.
Measure height, width and the path in. The 50-gallon units are about 22 inches across; the REHP65 and REHP80 are about 25.6 to 25.8. Rinnai’s manual asks for at least 6 inches on the left and 2 on the right, and recommends 20 inches above the unit for efficiency and filter service and 12 inches at the sides for service. Rinnai’s brochure and the Amazon listings say zero clearance on the sides; go by the manual. Senville lists 20 inches on top and 20 inches in front as minimums.
Plan the condensate drain. It needs a floor drain, a sink, or a condensate pump. If gravity drainage is impractical, our condensate pump comparison explains flow at lift, temperature limits, service clearance and overflow protection; confirm the heater’s exact pump requirements before choosing. Rinnai says the pump must handle at least 2 gallons a day and the line cannot empty into the drain pan.
Add a drain pan and an expansion tank. Rinnai lists a missing drain pan as improper installation that its warranty does not cover, and its manual says the pan must be used with Rinnai’s leak kit (sold separately) where spilled water could cause property damage. Both manuals call for an expansion tank on a closed system, where a check valve or backflow preventer sits on the cold line. See water heater drain pans and water heater expansion tanks.
Size by first-hour rating. ENERGY STAR suggests starting from the capacity of your current tank. Compare first-hour ratings, not tank gallons; our water heater size calculator walks through it.

Living With a Heat Pump Water Heater

It cools and dries the room it sits in. ENERGY STAR notes that this helps in hot, humid months; in winter it means a cooler basement or utility room. Senville’s manual tells installers to consider noise in living areas and to avoid a wall shared with a neighbor’s bedroom, because the unit is expected to run at night. If you are weighing it against other options, our heat pump vs tankless water heater guide covers where each one fits.

Maintenance is heavier than a plain electric tank. Rinnai says to clean the washable air filter every 3 months, pour a cup of bleach down the condensate line at least once a year, drain a few quarts from the tank every month for sediment, and replace the anode about every 5 years, sooner depending on water use and quality. Senville lists filter cleaning, bleach in the condensate line and draining the tank as yearly tasks. Rinnai’s warranty terms say that ongoing maintenance is to be done by a professional contractor, licensed where required, and logged in Rinnai’s Installation and Service Record, so budget for service visits if you want to keep the 10-year coverage. The manual’s care section reads like owner tasks and does not say which ones Rinnai needs a professional for, so ask your installer to cover them in a logged service plan. Leave Economy mode on unless you run short: Rinnai recommends it to maximize electricity cost savings, while Hybrid mode runs the elements alongside the heat pump and E-Heater mode runs only the elements, like a standard tank. By default, Rinnai’s current manual has both switch back to Economy after 72 hours. Rinnai lists its own replacement anode for these units (one part for the 50 and 65, another for the 80) and publishes separate anode replacement instructions. Its manual warns that removing the anode voids the warranty, the warranty does not cover parts replaced during recommended maintenance, and Rinnai’s anode instructions have you drain the tank and take off the top cover and display box. While the warranty runs, have your service contractor do the swap with the Rinnai part and log it. Our anode rod size and type guide explains the rod types.

FAQ

Is a hybrid water heater the same as a heat pump water heater?

Yes. ENERGY STAR says heat pump water heaters are also called hybrid electric water heaters. The hybrid part is the backup resistance elements, which take over when the room air is out of range or demand is high.

How much space does a heat pump water heater need?

Rinnai’s current manual says a room larger than 700 cubic feet of free space (for example 8 by 8.75 by 10 feet) needs no extra ventilation, a room of 85 to 700 cubic feet needs a fully or double louvered door, and a space under 85 cubic feet needs ducting. From 85 to 450 cubic feet, Rinnai’s closet and ducting rules also apply and do not fully agree, so either duct it or also meet the closet rule (louver level with the air exhaust, exhaust within 12 inches of the door, 24 square inches of gap under it), and have your installer confirm the layout with Rinnai. ENERGY STAR recommends 1,000 cubic feet of air space. Senville’s manual has no small-room rule and says to allow 200 cubic meters (about 7,000 cubic feet, our arithmetic) of free space. For clearances, Rinnai’s minimum is zero on the top and back, 6 inches on the left and 2 on the right, but it recommends 20 inches on top for efficiency and filter service and 12 inches at the sides for service. Senville lists 20 inches on top and 20 inches in front as minimums.

Can a heat pump water heater go in a garage?

It can if the garage does not freeze. Rinnai’s heat pump runs with room air between 37 and 107°F by its spec sheet (108°F in the manual) and Senville’s between 37 and 109°F. Below that the elements do the work, and it runs like a standard electric tank. Both manuals say to protect the heater and water lines from freezing, and ENERGY STAR recommends a space that stays between 40 and 90°F all year. Rinnai’s warranty also excludes freeze damage, damage from dust, lint or drywall particles in the air, and use around chemicals such as chlorine or hair spray, so keep it away from workshop dust and stored pool chemicals.

Does a heat pump water heater need a drain?

Yes. The heat pump makes condensate. Rinnai says to pitch the line down at least 1/8 inch per foot, add a P-trap if it goes to a sewer pipe, use a condensate pump rated at least 2 gallons a day if there is no drain, and never run it into the drain pan. Both makers say the condensate is not acidic and needs no neutralizer. The relief valve line still runs to its own open drain.

Is a heat pump water heater a DIY install?

Check your state first. Rinnai’s warranty applies only to a qualified product installation, which it defines as an installer licensed where your state requires one, working to Rinnai’s documents and local codes. The job is the same plumbing and 240-volt wiring as an electric tank plus a condensate drain, but losing a 10-year warranty on a unit this size is a bad trade.

Why Trust Plumbing Picks

Plumbing Picks is written by a licensed Georgia journeyman plumber. Every size, rating and spec on this page comes from the manufacturer documents and ENERGY STAR listings below, which we opened and read, or from the Amazon listing we link; nothing here comes from hands-on testing. When we checked on September 29, 2026, each linked unit was listed in stock on Amazon. The three Rinnai units are sold by eFaucets, a third-party seller on Rinnai’s authorized e-tailer list, and the Senville is sold by Senville. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.

Sources

Bottom Line

Check the room first: 700 cubic feet of air, or a louvered door or duct kit, by Rinnai’s rule; a condensate drain; and a 30-amp 240-volt circuit. If it passes, the Rinnai REHP50 is the unit to buy for most homes, and the REHP65 is the step up when 50 gallons runs short. The Senville is the pick if you want to buy from the maker, but Senville asks for 200 cubic meters of free space around the unit, so plan it for a large basement or garage or get Senville’s written guidance first. Have a licensed plumber install it, and for a Rinnai have a professional do the maintenance and log it, because the warranty depends on both.