Rheem Tankless Water Heaters

Rheem is unusual in offering a serious gas tankless range and a serious electric one. They are very different products with very different documentation quality, so this page treats them separately.

Quick picks

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Ranked picks with what each one is best for, our score and a link to check the current price on Amazon.

#	Product	Best for	Price
1	Rheem Prestige RTGH-95DVLNThe condensing gas tankless most houses should start with: 5.5 GPM at a 70°F rise covers two showers in a cold-inlet climate, and the 12-year residential heat exchanger warranty is the longest on this list.	Most whole-house gas jobs	Check price on Amazon No live price feed on this site, so we show none. #ad
2	Rheem Professional Classic RTEX-24The value electric unit: 24 kW, 5.9 GPM rated flow and a digital set point in 1°F steps, from a brand whose parts your local supply house actually stocks.	Electric tankless on a budget	Check price on Amazon No live price feed on this site, so we show none. #ad

The picks in full

Pick 1 — Most whole-house gas jobs

Rheem Prestige RTGH-95DVLN

The condensing gas tankless most houses should start with: 5.5 GPM at a 70°F rise covers two showers in a cold-inlet climate, and the 12-year residential heat exchanger warranty is the longest on this list.

Published specifications for the Rheem Prestige RTGH-95DVLN

Fuel	Natural gas (LP variant sold separately)
Gas input	Up to 199,900 BTU/h
Flow at a 70°F rise	5.5 GPM
Maximum flow	9.5 GPM at a 35°F rise
Efficiency	Up to 0.93 UEF, stainless condensing heat exchanger
Minimum activation flow	0.4 GPM
Venting	Up to 150 ft of 3-inch PVC; 60 ft of 2-inch PVC
Dimensions	18-1/2 in W x 9-3/4 in D x 27-1/2 in H
Warranty	12-year heat exchanger (residential), 5-year parts, 1-year labor

What is good

• +The 70°F-rise figure is published, so you can size it honestly instead of guessing from the headline number
• +Condensing design vents in PVC, which is far cheaper to run than stainless category III pipe
• +0.4 GPM activation means a trickle at a bathroom faucet still fires the burner
• +Long PVC vent runs let you put it where the gas line already is

What is not

• −Needs a gas line sized for nearly 200,000 BTU/h — many existing 1/2-inch runs are not
• −Condensate has to go somewhere, which means a drain or a condensate pump
• −Annual descaling is not optional on hard water

Skip it if: Skip it if your gas meter and line cannot carry 199,900 BTU/h. Upsizing the gas line is often the single largest cost in a tankless conversion, and no amount of unit quality fixes a starved burner.

Check price on Amazon

No live price feed on this site, so we show none. #ad

Specifications above from Rheem RTGH series specification sheet (PDF); Pace Supply listing, RTGH-95DVLN, 199 kBtu/hr. We have not tested this unit ourselves.

Pick 2 — Electric tankless on a budget

Rheem Professional Classic RTEX-24

The value electric unit: 24 kW, 5.9 GPM rated flow and a digital set point in 1°F steps, from a brand whose parts your local supply house actually stocks.

Published specifications for the Rheem Professional Classic RTEX-24

Output	24 kW at 240 V
Rated flow	5.9 GPM
Breakers	3 x 40 A
Service required	200 A
Thermal efficiency	99.8%
Set point range	80 - 140°F in 1°F increments

What is good

• +Parts and warranty support through a brand with national distribution
• +Digital set point in single degrees rather than a notched dial
• +99.8% thermal efficiency: effectively all the electricity lands in the water
• +Cheaper than the German-built alternatives at the same kW

What is not

• −Rheem quotes a rated flow rather than a published rise-versus-flow curve
• −Three 40 A circuits and a 200 A service requirement
• −No flow control, so high flow shows up as lower temperature

Skip it if: Skip it if you want to size from published data. Rheem lists a rated GPM without the temperature rise it was measured at, so you cannot check the number against your own inlet temperature the way you can with the Tempra.

Check price on Amazon

No live price feed on this site, so we show none. #ad

Specifications above from Rheem RTEX-24 / RTEX-27 product page; Pace Supply listing, RTEX-24, 240 V 24 kW 100 A. We have not tested this unit ourselves.

The Prestige RTGH gas range

This is the line we recommend for most gas tankless conversions, and the reason is documentation as much as hardware. Rheem publishes the rise-qualified flow figure that lets you size the unit against your own inlet temperature.

The venting advantage

Up to 150 feet of 3-inch PVC is a long run, and it matters more than it sounds. Non-condensing units need stainless category III flue at several times the cost per foot, so on an awkward vent route the PVC capability can save more than the price difference between two heaters. Condensing vs non-condensing.

The RTEX electric line

The RTEX-24 and RTEX-27 are capable units with a real advantage: Rheem's national distribution means parts and warranty support are straightforward, which is not true of every electric tankless brand.

The gap in that table is the problem. A rated 5.9 GPM without a stated temperature rise cannot be checked against your own inlet temperature, which means you cannot size the unit honestly from the published data. Compare that with Stiebel Eltron, which publishes maximum rise at four flow rates on both 240 V and 208 V.

That is the only reason we rank the Tempra 24 Plus above the RTEX-24 in our electric tankless roundup, despite the RTEX's better distribution.

Which Rheem tankless, by situation

• Gas available, whole house, any climate → Prestige RTGH-95DVLN.
• Gas available, long or awkward vent route → Prestige RTGH, for the 150 ft PVC capability.
• No gas, warm-inlet climate, 200 A service → RTEX-24, accepting that you will have to confirm its output at your rise with Rheem rather than from the listing.
• No gas, cold climate, whole house → neither. A cold-inlet whole-house electric tankless install is where this technology disappoints. Consider a heat pump water heater instead.

The warranty condition

Two Rheem-specific points that apply here. Residential warranty requires online registration within 90 days of installation. And the residential tankless gas limited warranty is available only to the original owner at the original installation location and is not transferable — which is worth factoring in if you may sell the house. Rheem warranty terms.