Rheem Tankless Water Heaters: Models, Features, and Specifications

Rheem Manufacturing Company produces one of the broadest tankless water heater lineups available in the North American residential and light commercial market, spanning gas-fired and electric configurations across multiple efficiency tiers. This page covers Rheem's principal model families, their defining technical specifications, fuel-type classifications, Uniform Energy Factor (UEF) ratings, and the regulatory and installation contexts that govern their deployment. The tankless providers provider network indexes contractors qualified to install and service these units across U.S. jurisdictions. Accurate specification and code-compliant installation depend on matching each Rheem product line to its applicable load requirements and local permitting authority.

Definition and scope

Rheem tankless water heaters are on-demand appliances that heat water only when a flow event is detected, eliminating the standby heat loss associated with conventional storage-tank units. Rheem markets these products under two primary sub-brands: the Rheem label for the full residential and commercial range, and the Richmond label for distribution through specific retail channels, primarily hardware and home improvement stores.

The scope of Rheem's tankless portfolio divides into three primary classifications:

1. Gas-fired condensing units — High-efficiency models with secondary heat exchangers that recover latent heat from flue gases, achieving UEF ratings typically between 0.90 and 0.96. These require Category IV PVC or CPVC venting and a condensate drain.
2. Gas-fired non-condensing units — Mid-efficiency models using single-pass stainless or copper heat exchangers, requiring Category III stainless steel venting and no condensate management. UEF ratings in this class generally fall between 0.82 and 0.88.
3. Electric tankless units — Both whole-house and point-of-use (POU) configurations. Whole-house units are rated from approximately 13 kW to 36 kW; POU units typically fall between 2.5 kW and 7 kW.

Rheem's Performance, Performance Plus, and Prestige series represent the three principal residential tiers within the gas condensing and non-condensing categories, with the Prestige series occupying the highest efficiency band.

How it works

All Rheem tankless units operate on a flow-activated ignition or resistance-heating principle. When demand at a fixture drops the line pressure, a flow sensor triggers either a gas burner modulation sequence or an electric resistance element. The heat exchanger — copper in non-condensing models, stainless steel in condensing models — transfers heat to the water stream as it passes through the unit.

Gas-fired Rheem units use a modulating gas valve that scales BTU output in proportion to incoming flow rate and inlet water temperature. The Performance Platinum series, for example, carries a maximum input rating of 199,000 BTU/hr with a flow rate capacity up to 9.5 GPM at a 35°F temperature rise (Rheem product specification sheets, available through Rheem's product registration portal). At a 77°F rise — the standard Department of Energy test condition under 10 CFR Part 430 — rated GPM outputs are lower.

Electric Rheem units rely on self-modulating technology in higher-end configurations, adjusting wattage draw in proportion to demand. Lower-cost fixed-wattage models apply constant power regardless of flow rate, making them more appropriate for POU applications than whole-house service.

Venting configurations for gas units follow ANSI Z21.10.3 standards for gas water heaters with input ratings above 75,000 BTU/hr. The National Fuel Gas Code (NFPA 54) and local mechanical codes govern vent material selection, clearances, and termination requirements.

Common scenarios

Rheem tankless units appear across four primary deployment contexts:

• Whole-house residential replacement — A Performance Plus or Prestige condensing unit replaces a 40- or 50-gallon storage tank. The installer sizes the unit to peak simultaneous demand, typically two showers plus a dishwasher, requiring a unit rated at 7.0–9.5 GPM at the local groundwater temperature rise.
• New construction specification — Builders in energy code jurisdictions following IECC 2021 (adopted in whole or in part by over 30 states as tracked by the U.S. Department of Energy Building Energy Codes Program) frequently specify condensing tankless units to meet water heating efficiency minimums.
• Supplemental or recirculation configurations — A Rheem unit paired with a dedicated recirculation pump and timer, or the brand's built-in recirculation capability available on select Prestige models, addresses hot-water delivery lag in larger homes.
• Light commercial applications — Rheem's commercial condensing series, including the RTGH-C and similar model families, serves restaurants, small hotels, and medical office buildings where continuous on-demand output is required.

Decision boundaries

Selecting among Rheem's model tiers involves discrete technical and regulatory thresholds:

1. Efficiency requirements by jurisdiction — The U.S. Department of Energy's National Appliance Energy Conservation Act (NAECA) mandates minimum UEF thresholds for residential water heaters. As of the 2015 rulemaking (effective April 16, 2015), gas-fired tankless units with input ratings up to 200,000 BTU/hr must meet a minimum Energy Factor of 0.82 (equivalent UEF approximately 0.87), as published in 10 CFR Part 430.
2. Venting material classification — Condensing vs. non-condensing is not a preference decision; it determines permissible vent materials. Using PVC on a non-condensing unit violates NFPA 54 and manufacturer installation instructions, voiding both the warranty and UL provider.
3. Electrical service for electric units — A 36 kW whole-house electric unit requires a 150-amp dedicated service in most configurations. Homes with 100-amp total service panels cannot accommodate whole-house electric tankless without a panel upgrade, a permitting-triggered scope item in all U.S. jurisdictions.
4. Gas supply sizing — Rheem Performance Plus gas units require a minimum 3/4-inch gas supply line for units above 150,000 BTU/hr input; inadequate supply pressure is the leading cause of cold-water sandwich events and low-flow lockout in field installations.
5. Permitting and inspection — Tankless water heater replacements trigger mechanical permits in the majority of U.S. municipalities. Installations involving new gas piping, electrical service changes, or venting modifications typically require separate trade permits and final inspections. The tankless provider network purpose and scope page describes how this reference site structures contractor and permitting information by service category.

The distinction between condensing and non-condensing units also carries long-run cost implications: condensing units cost more to purchase but recover BTU content that non-condensing units exhaust, reducing operating costs over time. For climates with groundwater temperatures below 55°F — common in the northern tier of the U.S. — the efficiency differential is amplified because the unit must work harder to achieve the target delivery temperature, making the condensing tier the standard specification choice in those regions. Professionals navigating unit selection across project types can reference the broader how to use this tankless resource page for context on how this site organizes its technical and provider network content.