Rheem RTEX-18 Tankless Water Heater: Efficiency, Performance & Value

A Comprehensive Review of the Rheem RTEX-18 Tankless Water Heater

The Rheem RTEX-18 is a high-performance tankless electric water heater engineered to provide instant, continuous hot water while maximizing energy efficiency. Designed for residential use, this compact yet powerful unit eliminates the need for a bulky storage tank, heating water only when needed to reduce energy consumption and lower utility costs. With advanced self-modulating technology, the RTEX-18 adjusts power usage based on demand, ensuring optimal performance whether supplying a single fixture or supporting multiple applications. Its sleek, space-saving design, durable copper immersion heating elements, and precise digital temperature control make it a versatile and reliable choice for homeowners looking to upgrade to a more efficient and convenient water heating system.

Key Features

• On-Demand Hot Water: The RTEX-18 heats water only when needed, ensuring a continuous supply without the energy losses associated with traditional tank heaters.
• Compact and Stylish Design: Its sleek, space-saving profile allows for flexible installation in tight spaces, making it ideal for homes with limited utility area.
• Digital Temperature Control: Equipped with an external digital thermostat, users can easily adjust the water temperature in 1°F increments, ranging from 80°F to 140°F, providing precise control over comfort levels.
• Energy Efficiency: With a 99.8% energy efficiency rating, the RTEX-18 is designed to reduce energy consumption, potentially leading to significant cost savings on utility bills.
• Durable Heating Elements: The unit features robust copper immersion heating elements with brass tops, engineered for durability and easy replacement, ensuring long-term reliability.

Performance and Applications

The Rheem RTEX-18 is designed to deliver consistent, on-demand hot water for various household applications, making it an ideal choice for small to medium-sized homes, apartments, and secondary water heating solutions. Its 18kW power output ensures efficient heating, but its capacity is best suited for moderate water usage needs.

Here’s a breakdown of its typical performance per fixture:

• Standard Hand Sinks: Approximately 0.5 gallons per minute (GPM).
• Washing Machines: Between 1 to 1.5 GPM.
• Kitchen Sinks and Dishwashers: Ranging from 1 to 2 GPM.
• Showers: Standard showerheads typically require about 2.0 GPM, while water-saver showerheads use around 1.5 GPM.

While the RTEX-18 is capable of handling multiple fixtures, its performance is dependent on groundwater temperature and simultaneous demand. In warmer climates, where incoming water temperatures are higher, it can comfortably support a shower and a sink simultaneously. However, in colder regions, where incoming water requires more heating, users may experience a drop in flow rate if multiple fixtures are in use at once.

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Installation Considerations

The Rheem RTEX-18 is an electric tankless water heater that requires careful attention to electrical specifications to ensure safe and efficient operation. Unlike traditional water heaters that simply plug into a standard outlet, this unit has specific power demands that must be met for proper functionality.

• Voltage: 240V
• Amperage: 75A
• Recommended Breaker Size: Two 40A double-pole breakers
• Wire Size: 8 AWG

Because of these power requirements, professional installation is strongly recommended to ensure compliance with local electrical codes and safety standards. In many cases, homeowners may need to upgrade their electrical panel to accommodate the unit, especially in older homes with lower amperage service. Some users have reported that upgrading their panel added to the initial installation cost, so it’s important to factor this into the total budget when considering the RTEX-18.

Additionally, proper placement and water line connection are crucial for optimal performance. The unit should be installed in a well-ventilated area, away from excessive moisture or direct sunlight. It is also recommended to have a licensed electrician assess your home’s electrical capacity before installation to prevent circuit overloads and ensure seamless operation.

Customer Feedback

Overall, the RTEX-18 has received positive reviews for its performance and reliability. Users appreciate the immediate availability of hot water and the unit’s compact size. Many homeowners report that the RTEX-18 performs exceptionally well for one or two fixtures at a time, making it a great fit for single-bathroom households, guest suites, and smaller homes. However, those with larger households or higher simultaneous hot water demands may need to consider a unit with a higher GPM rating or multiple tankless heaters for whole-home use.

Why We Love the RTEX-18

The Rheem RTEX-18 stands out as a compact, energy-efficient, and user-friendly tankless water heater designed for consistent on-demand hot water. With 99.8% energy efficiency, durable copper heating elements, and precise digital temperature control, it’s an excellent choice for smaller households and moderate water usage needs.

While it may struggle to support multiple high-demand fixtures simultaneously, it excels in providing continuous hot water for one to two fixtures. Rheem’s reputation for quality and strong warranty coverage adds peace of mind, making the RTEX-18 a top contender for homeowners looking to upgrade to a reliable and space-saving tankless water heater.

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