Rheem Tankless Water Heaters — Gas, Electric & Condensing Models

Choosing the Right Rheem Tankless Water Heater

The right tankless model comes down to three things: your fuel source, your home's hot water demand, and how energy-efficient you want the unit to be. Here's how the Rheem lineup breaks down.

Gas vs. Electric

Gas tankless water heaters (RTG and RTGH series) deliver the highest flow rates — typically 6.8 to 9.5 GPM — making them the right choice for whole-home hot water in 2 to 5+ bathroom homes. They require natural gas or propane and proper venting. Electric tankless water heaters (RTEX series) install in tighter spaces, require no venting, and run on standard 240V wiring. The RTEX-24 and RTEX-27 can handle a 2-bathroom home in warmer climates, while the RTEX-36 supports larger applications.

Sizing by Bathroom Count

A practical rule: count the hot-water-using fixtures that might run at the same time, then size the unit by GPM. The Rheem RTG-70 series (7.0 GPM) covers most 2-bathroom homes. The RTG-84 and RTGH-84 (8.4 GPM) handle 2-3 bathrooms. The RTG-95 and RTGH-95 (9.5 GPM) cover 3+ bathroom homes. In colder climates with higher groundwater temperature rise requirements, size up one tier — what handles 3 bathrooms in Florida may only handle 2 in Wisconsin.

Condensing vs. Non-Condensing

Non-condensing models (RTG series) use a single heat exchanger with metal venting and are the lower-cost option. Condensing models (RTGH series) capture additional heat from exhaust gases through a secondary stainless steel heat exchanger, reaching up to 0.93 UEF efficiency, and can vent through standard PVC pipe — saving meaningful cost on long vent runs. The RTGH series typically pays back the price difference within 4-7 years through reduced gas consumption, and its 15-year heat exchanger warranty is the longest in the category.

When a Combi Boiler Makes Sense

Rheem ThermaForce combi boilers (RCBH and RHBH series) handle both space heating and domestic hot water from a single wall-mounted unit. They're ideal for whole-home renovations where you'd otherwise need both a furnace and a separate water heater, and they free up significant utility-room space. Models range from 99K to 199K BTU.