Rheem 18kW 240V Tankless Water Heater: In-Depth Review

The Rheem 18kW 240V Tankless Electric Water Heater is a highly efficient and compact solution designed to meet the hot water needs of residential and light commercial applications. In this review, we will explore the key features, specifications, performance, customer feedback, as well as the pros and cons of this tankless water heater. Whether you are considering upgrading to a tankless system or replacing an old tank-style heater, this review will provide valuable insights into whether the Rheem 18kW model is the right choice for you.

Key Features and Specifications

Key Features

• Powerful Performance: This water heater delivers a flow rate of up to 4.4 GPM, providing sufficient hot water for multiple applications simultaneously, such as showers or sinks.
• Energy Efficiency: With its self-modulating technology, the Rheem 18kW heater adjusts power usage based on the demand for hot water. This results in substantial energy savings and a reduction in overall water heating costs.
• LED Digital Display: The heater comes with a digital temperature display, allowing for precise temperature control with a +/-1 degree accuracy.
• Compact Size: The sleek, compact design takes up significantly less space compared to traditional water heaters. It can be installed under a sink, in a bathroom, or in a closet, making it ideal for homes with limited space.
• No Venting Requirement: Unlike gas-powered tankless water heaters, the Rheem 18kW does not require any venting, simplifying installation and expanding the possibilities for installation locations.
• Durability: The water heater is equipped with copper immersion heating elements that are field-serviceable, ensuring long-lasting performance with easy maintenance.

Specifications

Specification	Details
Brand	Rheem
Product Dimensions	14.5″W x 18.25″H
Power	18 kW
Voltage	240V
Flow Rate	Up to 4.4 GPM
Material	Stainless Steel
Item Weight	14.78 Pounds
Temperature Control	External Digital Thermostat
Wattage	18,000 watts
Capacity	18 Gallons (depends on usage)
Installation	Bottom 3/4 inch NPT water connections
Color	Gray

Performance

The Rheem 18kW 240V Tankless Water Heater is designed to perform well in moderate to large homes, offering an adequate hot water supply for typical household needs. The self-modulating feature allows the unit to automatically adjust its energy consumption based on the demand for hot water.

In terms of performance, it can heat water on-demand, ensuring that hot water is always available without the wait associated with traditional tank heaters. With a maximum flow rate of 4.4 GPM, it can serve multiple points of use simultaneously, including two bathrooms or a shower and two sinks. This makes it an excellent choice for smaller to medium-sized homes or apartments where multiple hot water sources may be needed.

One of the most attractive aspects of this water heater is its energy efficiency. Unlike tank-based water heaters, which continually heat and store water, the Rheem 18kW tankless model only uses electricity when water is being drawn. This ensures that energy is not wasted, resulting in lower energy bills. According to the Department of Energy, tankless electric models like this can save up to 34% on water heating costs when compared to traditional tank heaters.

However, while the performance is generally good, some users have reported issues with fluctuating water temperatures. Although many found the water temperature to be consistently hot, a few customers experienced periods of lukewarm water or fluctuating temperature. These issues could be related to installation or water flow conditions, but they are worth considering if you are in an area with inconsistent water pressure or fluctuating ground temperatures.

Customer Feedback

The Rheem 18kW Tankless Water Heater has received a mix of positive and negative reviews from customers.

Positive Feedback

• Energy Efficiency: Many customers have praised the unit for its energy-saving capabilities, noting that their utility bills have dropped significantly after installing the Rheem tankless water heater.
• Compact Size: Several users have mentioned that the small size of the unit allows them to save space, which is particularly useful for those living in small apartments or homes with limited storage space.
• Ease of Installation: Several customers noted that the unit is relatively easy to install, especially compared to traditional tank water heaters. Its compact design and simple connections make it a good option for DIY installation, though some customers do recommend hiring a professional electrician.
• Continuous Hot Water: The majority of users found that the water heater provided a steady supply of hot water, even for households with multiple bathrooms or simultaneous hot water usage.

Negative Feedback

• Temperature Fluctuations: A number of customers have experienced inconsistent water temperature. While some report the water being too hot, others complain about it being lukewarm, especially when multiple points of use are in operation. This could indicate issues with the unit’s temperature modulation or water flow, or it could be related to the specific installation conditions.
• Short Lifespan: Some customers have raised concerns about the longevity of the unit, citing that their water heater broke down within a year of use. The quality of customer support in addressing warranty claims has also received mixed reviews, with some users expressing frustration over long response times.
• Size: While the compact size is praised by those in smaller homes or apartments, a few customers with larger homes have found that the unit was not sufficient to meet their needs, particularly in colder climates or with multiple bathrooms.

Pros and Cons

Pros

• Energy-Efficient: Reduces energy usage by heating water only when needed.
• Compact and Space-Saving: Ideal for homes with limited space.
• Digital Temperature Control: Allows for precise control over water temperature.
• Self-Modulating Technology: Adjusts energy consumption based on water demand, helping save on electricity costs.
• No Venting Required: Easy to install in various indoor locations.
• Durable Heating Elements: Copper immersion heating elements are long-lasting and field-serviceable.

Cons

• Inconsistent Temperature: Some users experience fluctuating water temperatures, especially when using multiple hot water outlets simultaneously.
• Short Lifespan for Some Units: Several users reported that the unit stopped functioning within a year of use.
• Limited for Larger Homes: May not be sufficient for large households or homes with multiple bathrooms, particularly in colder climates where the incoming water temperature is lower.

Final Verdict

The Rheem 18kW 240V Tankless Electric Water Heater is a solid choice for homeowners looking for an energy-efficient, space-saving water heating solution. Its self-modulating technology ensures that energy is only consumed when hot water is needed, potentially saving users up to 34% on their water heating costs. The compact size and easy installation process make it ideal for small homes, apartments, or those looking to free up space.

However, there are some drawbacks to consider. While the unit performs well for many users, some have experienced fluctuating water temperatures, especially when multiple points of use are active at the same time. Additionally, there have been reports of the unit failing within a year of installation, so it is important to consider the warranty and customer service responsiveness.

Check out our reviews of the best tankless water heaters below:

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• Best Natural Gas Tankless Water Heater
• Best Non-Condensing Tankless Water Heater
• Best RV Tankless Water Heate