Rheem RTEX-13 Tankless Water Heater review

The Rheem RTEX-13 Tankless Water Heater provides hot water fast and at a low price.

Rheem RTEX-13 Tankless Water Heater review
(Image: © Amazon)

Top Ten Reviews Verdict

The Rheem RTEX-13 Tankless Water Heater provides good value for money and has self-modulating power.


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    LED display controls

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    Not suitable for large houses

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    Not suitable for really warm areas

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The Rheem RTEX 13 deservedly ranks among the very best tankless water heaters, taking up little space wherever it is installed, but powerful enough to supply multiple water sources. Weighing in at 8.5 pounds, it is 8.25 inches wide and 12.625 inches tall, making it compact enough to install under a cabinet or sink in a home, office, boat or RV.

This compact electric tankless water heater allows you to control water temperature from a panel built into the front of the unit, while the heater also has a thermostat dial that allows for the adjustment of temperature over nine settings.

Rheem RTEX-13 Tankless Water Heater: What you need to know

The Rheem Tankless Electric RTEX 13 only requires 0.3 gpm to activate its heating elements. It can also put out a maximal flow of 4.8 gpm. This provides continuous hot water for two faucets and a shower. However, just as with other tankless water heater brands, the flow rate depends on temperature difference between the incoming cold water and the hot water coming out of the unit. According to some experts, if you live in a very cold area this unit may not work as well as in warmer climates. This is true of other tankless water heaters as well, not just the Rheem.

The RTEX 13 uses a rugged brass and copper immersion heat exchanger. It is an energy efficient water heater that modulates power consumption while providing a continuous hot water supply. It is a 13-kilowatt heater that requires 240 volts and 54 amps of electricity. However, 54 amps is quite a high energy draw, and just like with most electric tankless water heaters, you need to install a 60-amp breaker box or the RTEX 13 may trip your regular breaker and dimming house lights.

Rheem RTEX-13 Tankless Water Heater: Where it can be used

You can use this Rheem tankless water heater for residential or industrial applications. While it can heat water for a small apartment or double-occupant housing unit, it is best suited as a point-of-use water heater. You should only install it to cover a maximum of three fixtures that are not far from the heater. As a single point-of-use heater, the RTEX 13 can serve a garage, shop, laboratory, boat or RV. A 3-foot electric power cable is provided for your convenience. 

Rheem RTEX-13 Tankless Water Heater: User reviews

The Rheem RTEX-13 Tankless Water Heater scored an average of 4.4 out of five stars on Amazon. One reviewer claimed, 'this will save you money and you won't run out of hot water'. However, they also pointed out that this tankless water heater isn't Energy Star certified. Other reviewers stated that this water heater is 'perfect for a single bathroom'. Some users, however, claim this unit 'only lasts two or three years max'. 

Should you use the Rheem RTEX-13 Tankless Water Heater?

The Rheem RTEX-13 is a space-saving electric tankless water heater to replace bulky, inefficient water heaters. Although it is energy efficient, you have to modify your home electricity to supply 240 volts and 60 amps. Unlike the EcoSmart ECO 27, the RTEX 13 is not optimal for cold climates, but it works great for a garage, office, boat, RV or double-occupant house.

John Carlsen

John has been researching and reviewing home security and smart home products for Top Ten Reviews since 2013. As well as covering smart home and home security and safety, he also covers other home technology products such as HVAC, garage door openers and more. He enjoys DIY, writing and hiking in his spare time.