Rheem Gas/Electric Tankless Water Heater Reviews and Buying Guide 2021

Before you dive into the specific brand review, we highly recommend you to read our elaborate Tankless Water Heater Reviews and Tankless Water Heater Installation Cost Guide in advance. There are several crucial steps you need to take before you even start to think about the brand.

Our Rheem tankless water heater review guide is detailed and accurate. You’ll find specifications for all models summarized in a table plus an explanation of Rheem features. A table of Rheem tankless water heater prices is included.

See our buying guides to other popular brands that contain the same information about each. They make it easy to research and compare the brands you’re considering. We’ve prepared guides for these popular tankless water heater brands:

Introduction to Rheem Tankless Water Heaters

Rheem is one of the largest manufacturers of water heaters in North America. Long an American company, Rheem and it’s subsidiary Ruud are now owned by Paloma Industries which is headquartered in Nagoya, Japan.

The Rheem lineup of tankless water heaters is large and impressive. The company produces both gas and electric units in a range of sizes from point-of-use electric to whole-house gas tankless water heaters.

Rheem makes two broad categories of tankless water heaters:

  • Professional Line: These models are available only through Rheem (and Ruud) dealers as a package deal that includes installation. Models from Professional Line usually are started with “RTGH” and “RTEX”.
  • Performance Line: These Rheem tankless water heaters are sold in home improvement stores and online. In all cases, the units are very similar to Professional Series models – often they are identical. Models from Performance Line usually are started with “ECOH” and “RETEX”.

The Professional and Performance water heaters include models that are very similar. The choice comes down to whether you’re willing to pay a premium to get the unit and installation from a Rheem dealer or whether you’d prefer to shop around to find more competitive pricing from qualified installers in your area.

This table shows all current Rheem tankless gas and electric water heaters.

Rheem Gas Tankless Water Heater Models

Electric ModelsKWEfficiencyMax. GPMWarranty
3699.88.85 years
2799.86.65 years
2499.85.95 years
1899.84.45 years
1399.83.25 years
1199.82.75 years
899.81.95 years
699.81.55 years
3.599.80.95 years

Rheem Gas Tankless Water Heater Models

Gas ModelsMax BTUEF/UEFMax. GPMCirculatingIndoor/OutdoorWiFiWarrantyCondensing
Prestige RTGH-RH11199K.96/.9411Built-inIndoorNo12 yearsYes
Prestige RTGH-10180K.96/.949.9Built-inIndoorNo12 yearsYes
RTGH-95199K.96/.939.5AvailableIndoor/OutdoorYes12 yearsYes
RTGH-90180K.96/.939AvailableIndoor/OutdoorYes12 yearsYes
RTGH-84157K.96/.938.4AvailableIndoor/OutdoorYes12 yearsYes
ECOH200DVLN199K.96/.9311Built-inIndoorNo12 yearsYes
ECOH180DVLN180K.96/.939.9Built-inIndoorNo12 yearsYes
ECOH180180K.96/.949AvailableIndoorYes12 yearsYes
ECOH180XLN180K.96/.949AvailableOutdoorYes12 yearsYes
ECOH160DVLN157K.96/.938.4AvailableIndoorYes12 yearsYes
ECOH160XLN157K.96/.938.4AvailableOutdoorYes12 yearsYes
ECO200199K.82/.829.5AvailableIndoor/OutdoorOptional12 yearsNo
ECO180180K.82/.828.4AvailableIndoor/OutdoorOptional12 yearsNo
ECO160160K.82/.827AvailableIndoor/OutdoorOptional12 yearsNo

Important Note on Max. GPM: This column represents the maximum gallons per minute flow rate the heater can produce. Maximum GPM flow is achievable only when the incoming water is quite warm. The colder the incoming water is, the longer it must be heated to reach the thermostat setting on the tankless water heater, so the lower the GPM flow rate will be. In tankless water heater specifications, you’ll see information such as “Flow rate @ 70°F temp rise is 4.3 GPM.” That’s from a unit with Max. GPM of 7.5 GPM and means that if the temperature of the incoming water must be raised by 70 degrees Fahrenheit to reach the thermostat setpoint, then only 4.3 gallons per minute of hot water can be expected. For more information on this important topic, see the related section in our Tankless Water Heater Buying Guide.


  • BTU Input: These numbers show the minimum BTUs the burners create when just a trickle of water is running and the maximum heat created when hot water is in high demand.
  • NG/LP: NG is natural gas; LP is liquid propane.
  • EF/UEF: EF is an older rating called Energy Factor. UEF is the newly instituted rating Uniform Energy Factor. Both rate the unit’s efficiency.
  • Energy Star models: Rheem condensing water heaters are Energy Star compliant.
  • Effective BTUs: To determine how many BTUs are used to create hot water vs. being lost through exhaust gases, multiply the Input BTUs by the model’s efficiency. Example: The Performance Series Mid-efficiency Indoor with 199,000 BTU input has a UEF of .82 or 82%. Therefore, 199,000 x .82 = 163,180 effective BTUs.
  • Alternate Series Names: The Performance Series condensing units are called Performance Platinum and Mid-efficiency units are called Performance Plus in some Rheem tankless water heater literature.

Rheem Tankless Water Heaters Features Analysis

Here are notable features that differentiate some Rheem models and are useful for comparing with other brands.

Built-in recirculation pumps are available on several Prestige and Performance Series condensing units and one Performance Mid-efficiency model. These are whole-house tankless water heaters installed in a central location. The purpose of the pumps is to circulate water that is periodically heated back to points of use. The advantage is not having to wait for hot water. This eliminates water waste and can be a money-saving feature for homes on metered water.

  • Corrosion-resistant models: Rheem condensing units are built with stainless steel heat exchangers that increase the units’ durability. Why condensing models are prone to corrosion and the pros and cons of condensing units are topics discussed here in our Tankless Water Heater Buying Guide.
  • Linking multiple units: Most Rheem gas-fired tankless water heaters can be installed in multiples of up to 2, 6 or 20 units depending on the equipment used for the connection. Gas units from most top brands can be linked for high-volume demand situations.
  • Low emissions: Rheem gas models meet strict Low-NOx and Southern California SCAQMD requirements.
  • WiFi: Models with built-in WiFi are equipped with Rheem’s EcoNet wireless technology that allows you to monitor and control your water heater with the app and a smart device. WiFi-optional units are wired for EcoNet, but it would have to be installed during or after water heater installation.
  • Gas line compatibility: Rheem’s largest gas units do not require an upgrade from a standard ½” gas line to a ¾’ pipe. This compatibility keeps installation costs down.

How Rheem Water Heaters Compare to Other Tankless Brands

Rheem makes one of the largest lineups of water heaters, both gas-fired and electric.

The mix of options including recirculation pumps, WiFi, Low-NOx and other features is the best on the market. This means you’ll more likely find a model that exactly fits your size requirement and purposes.

Rheem’s electric water heaters get average ratings; Rheem gas tankless models boast ratings well above average. No other brand we reviewed has a pro line available only through dealers and a standard line available online and at home improvement stores.

Rheem Tankless Water Heater Prices

As noted, Rheem Professional Series models are available only through local Rheem dealers. The models are basically the same as comparable Performance Series units, but installation is included in the package cost. The quickest way to get written estimates from local Rheem installers is to use the Free Local Quote service. There is no cost or obligation. The Rheem dealers are licensed and insured, and they know they’re competing for the work, so must provide their best pricing. Here are Rheem tankless prices for the Performance Series.

Rheem Gas Models
Unit Cost Only
Rheem Electric Models
Unit Cost Only
RTEX-36, RETEX-3636
RTEX-27, RETEX-2727
RTEX-24, RETEX-2424
RTEX-18, RETEX-1818
RTEX-13, RETEX-1313
RTEX-11, RETEX-1111
RTEX-08, RETEX-088$210
RTEX-06, RETEX-066$170
RTEX-04, RETEX-044$170

Tankless Water Heater Installation Cost

The Performance Series models can be bought at many home improvement stores including Home Depot and many online sellers. Local plumbers can be hired for the installation. Simply make sure the installer has experience installing the brand water heater you purchase. Feel free to use our Free Local Quote service to get written estimates with no obligation from several of the top installers where you live. They are prescreened for experience, and are licensed and insured.

Rheem tankless water heater cost for professional installation runs from about $600 to $1,500 including some supplies. Accessories might be extra. For example, recirculating equipment can cost an extra $500 or more.

Factors that affect cost include:

  • Whether the unit is installed outdoors (lower cost) or indoors (higher cost)
  • Whether an indoor unit is vented through a side wall (lower cost, and possible only on condensing units) or through the roof (higher cost)
  • What vent materials are used
  • Whether extra gas line or water pipe needs to be installed

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