Rheem Tankless Water Heaters

Rheem tankless units across four series, from the 18 kW electric RTEX to the 199,900 Btu/h IKONIC with a built-in recirculation pump. Gas models run 120,000 to 199,900 Btu/h and deliver 3.3 to 5.6 GPM at a 70°F rise. Every gas unit takes 3/4" MIP on water and gas, holds 85 to 140°F, and modulates down to 11,000 Btu/h.

The choice that decides the install cost is condensing or not. The RTG series is non-condensing: 0.81 to 0.82 UEF, a copper fin heat exchanger, and exhaust hot enough to require 3"/5" stainless concentric venting. The RTGH series condenses: 0.93 UEF, copper and stainless, and exhaust cool enough to vent through 2" or 3" PVC, CPVC or polypropylene. The condensing unit often costs more on the invoice and less on the wall, because the vent material is a fraction of the price. Run both numbers before you pick.

IKONIC is the top tier. The RTGH-S models carry a full stainless heat exchanger, 0.96 UEF, a 15-year exchanger warranty instead of 12, and an elevation rating of 10,200 feet against 8,400 for the rest. The SR variants add a factory recirculation pump, which removes the cost of a separate pump and crossover valve on a retrofit.

Outdoor models need no vent at all. The XL suffix is outdoor, DV is indoor direct vent. In a mild climate the outdoor unit deletes the entire venting line item.

Two things to check before ordering. Size the gas supply to the load, not to the connection: the 3/4" inlet is the fitting, and a 199,000 Btu/h unit on an undersized run will fault under demand. And on electric, read the amperage before the kilowatts: the RTEX-36 draws 150 A and wants four 40 A breakers, which most residential panels cannot give up.

Repair parts, vent kits, valve kits and recirculation components for these units are stocked separately.

Replacing a tank with a tank instead? See Rheem 40 gallon water heaters, gas and electric.

Find matching Rheem tankless repair parts and tankless valve kits, compare Navien and Noritz models, or see all tankless water heaters. Not sure which size? Read what size tankless water heater do I need.

Popular models: RTGH-95DVLN-3, RTGH-90DVLN-3, RTGH-84DVLN-3, IKONIC RTGH-S11I, RTEX-18 and RTEX-36.

Frequently asked questions

What is the difference between Rheem RTG and RTGH?

RTG units are non-condensing and need stainless concentric venting. RTGH units are condensing, rated 0.93 UEF, and vent through PVC, CPVC or polypropylene.

What do DV and XL mean in a Rheem model number?

DV is an indoor direct vent model. XL is an outdoor model that needs no vent pipe.

What replaces a Rheem RTGH-95DVLN-2?

The RTGH-95DVLN-3 lists the RTGH-95DVLN-2 and RTGH-95DVLN-1 as replaced models. Each product page shows a "Replaces" list where we have that data.

Which Rheem tankless has a built-in recirculation pump?

The IKONIC SR models, such as the RTGH-SR10I and RTGH-SR11I, include a factory recirculation pump.