Rheem RTEX-13 Review

Choosing the right electric tankless water heater often feels like a puzzle. A point-of-use unit may be too weak, while a large whole-home model demands a massive electrical upgrade. The Rheem RTEX-13 electric tankless water heater carves out a vital space in this landscape, emerging as a powerful, versatile, and high-value solution for a huge range of homes. It offers a significant step up in performance from entry-level models, making it a capable whole-home solution for many, without the extreme costs of the top-tier units.

As a powerhouse in Rheem's compact tankless series, the RTEX-13 is designed for homeowners who need more than the bare minimum. It’s for those in small homes in moderate climates, for apartments and condos with higher demands, or for anyone wanting a robust heater for a guest house or master suite that can confidently run a shower and sink at the same time.

Is the Rheem RTEX-13 the perfect sweet spot of power, price, and performance for your home? This definitive review will provide an exhaustive deep dive into this popular model. We will analyze its real-world performance, critical installation needs, long-term value, and how it compares to its closest competitors to give you all the information you need.

Rheem RTEX-13 Summary

Feature	Score
Heating Power & Output	8.5/10
Energy Efficiency	10/10
Ease of Installation	7.5/10
Build Quality & Durability	9/10
Value for Money	9.5/10
Best For	Small Homes, Apartments, High-Demand POU Applications
Overall Rating	⭐️⭐️⭐️⭐️☆ (4.3/5)

Buy Now: Buy the Rheem RTEX-13 now

The Bottom Line: The Rheem RTEX-13 is an exceptional electric tankless water heater that hits the sweet spot for a huge number of users. It offers enough power to be a reliable whole-home solution for small families in moderate climates, and it excels as a high-performance point-of-use heater for any application. Its balance of strong performance, a manageable single-breaker installation, and an affordable price point makes it one of the best overall values in the entire tankless market. Read our full, detailed review below.

Rheem RTEX-13 Specifications

The technical specifications for the RTEX-13 tell a story of increased power and capability, defining both its output and its requirements.

Feature	Value
Type	Compact Whole-Home Electric Tankless
Heating Power	13 kW
Voltage	240V
Required Breaker	1 x 60 Amp Double-Pole
Amperage Draw	54 Amps
Max Flow Rate	3.17 Gallons Per Minute (GPM)
Energy Factor	~0.99 (99.8% Thermally Efficient)
Dimensions	4.25” x 8.5” x 13”
Weight	8.5 lbs (3.8 kg)
Water Connections	3/4″ NPT
Warranty	5-Year (Heat Exchanger), 1-Year (Parts)

Rhem RTEX-13 Review

This is where we move beyond the numbers to understand what the RTEX-13's increased power means for your daily life. Its value is defined by its versatility and ability to handle tasks that smaller models struggle with.

Heating Capacity & Flow Rate: A Significant Step Up

The 13 kW heating element is what sets the RTEX-13 apart from entry-level models. That 2kW boost over an 11kW unit makes a tangible difference in its Gallons Per Minute (GPM) output, expanding its viability as a true whole-home solution. As always, its performance is a function of the temperature rise required.

Let's explore its capabilities in various real-world scenarios:

• Warm Climates (e.g., Florida, Arizona – Groundwater at 70°F): In these ideal conditions, the RTEX-13 performs beautifully. Needing only a 35°F rise to achieve a 105°F shower, it can deliver its maximum 3.17 GPM. This is enough power to run a strong shower (2.0 GPM) and a kitchen sink (1.0 GPM) simultaneously without issue, making it a confident whole-home solution for a small family.
• Moderate Climates (e.g., North Carolina, Tennessee – Groundwater at 60°F): This is where the RTEX-13 truly shines and justifies its existence. To achieve a 45°F temperature rise, it will produce a solid 2.6 GPM. This is perfect for running a single high-flow shower or two low-flow showerheads (at ~1.3 GPM each) at the same time. For a small family of 2-3 people in these regions, the RTEX-13 is often the perfect balance of power and price.
• Cold Climates (e.g., New York, Illinois – Groundwater at 45°F): While still not an ideal whole-home solution for the coldest states, the RTEX-13's performance is a marked improvement over smaller units. To achieve a demanding 60°F rise, it produces about 2.0 GPM. This is enough for one strong, satisfying shower. You wouldn't be able to run other fixtures at the same time, but it won't leave you with a weak, lukewarm stream. In these climates, it serves as a superb, high-power point-of-use heater for a master bathroom or guest suite.

Performance Verdict: The Rheem RTEX-13 is a highly capable and versatile heater. Its power output is substantial enough to move beyond basic POU applications and serve as a legitimate whole-home solution for a large portion of the country. Its simple, robust manual control dial allows for easy temperature modulation.

Energy Efficiency: On-Demand Savings

The RTEX-13 is a model of efficiency. Its 99.8% thermal efficiency means there is virtually no wasted energy in the heating process. All the electricity it draws is converted directly into hot water. The primary savings come from its tankless design:

1. Elimination of Standby Loss: It consumes no energy when idle. This is a huge advantage over a traditional 40-gallon tank heater, which constantly uses energy to keep its water reserve hot, day and night. This can lead to significant savings on your monthly electric bill.
2. Water Conservation: By delivering hot water quickly to the taps, it reduces the time and water wasted waiting for the temperature to rise.

For anyone upgrading from an old electric tank, the RTEX-13 offers a major boost in efficiency and a noticeable reduction in utility costs.

Installation & Setup: Powerful yet Manageable

A key advantage of the RTEX-13 is that it provides a significant power boost while still having a relatively manageable, single-breaker installation.

• Electrical Needs: It requires a single, dedicated 240V circuit protected by a 60-Amp double-pole breaker, connected with 6-gauge copper wire. While this is a heavy-duty circuit that absolutely requires professional installation, it is far less complex and demanding than the multi-breaker setups needed for larger 18kW+ units. Most homes with 150-Amp or 200-Amp main service can accommodate a new 60-Amp circuit without needing a full panel upgrade.
• Plumbing: It uses standard 3/4-inch NPT water connections, making it easy to tie into a home's main plumbing lines.
• Mounting: Its incredibly compact size (the same as the smaller RTEX-11) is a huge benefit. It can be installed in a small utility closet, basement, or garage, freeing up valuable floor space once occupied by a bulky tank heater.

Build Quality & Maintenance

Rheem has a long-standing reputation for building durable, reliable products. The RTEX-13 features a robust heating chamber and threaded, field-serviceable heating elements—a crucial feature for long-term ownership. The simple, intuitive manual control dial on the front is easy to use and less prone to issues than more complex electronic interfaces.

To ensure a long service life, periodic maintenance is key. A descaling flush every 1-3 years, depending on your water hardness, will prevent mineral buildup and keep the unit running at peak efficiency. This simple maintenance can dramatically extend the life of the heater beyond its warranty period. The RTEX-13 is backed by a solid 5-year warranty on the heating chamber and a 1-year warranty on parts.

Rheem RTEX-13 Pros & Cons

Pros	Cons
✅ Excellent power output for its size and price	❌ Not powerful enough for larger families or cold climates
✅ Great whole-home solution for small homes/apartments	❌ Lacks advanced digital or thermostatic features
✅ Manageable single-breaker (60A) installation	❌ Only a 1-year warranty on parts
✅ Highly energy-efficient with no standby heat loss
✅ Very compact and frees up significant space
✅ Trusted brand with a reputation for reliability

Rheem RTEX-13 Professional Recommendation

The RTEX-13 is a versatile workhorse that fits a wide range of applications perfectly.

This heater is an EXCELLENT SPECIFICATION for:

• Small families of 2-3 people in moderate climates.
• Apartments, condos, or townhouses with 1-2 bathrooms.
• As a “super-powered” point-of-use heater for a guest house or in-law suite with a shower and multiple sinks.
• Anyone on the edge of a temperate/cold climate zone where an 11kW unit would be insufficient.
• Homeowners wanting a significant performance upgrade over smaller POU heaters without the cost and complexity of larger, multi-breaker models.

A Professional would recommend an ALTERNATIVE if:

• The family has 4 or more people and frequent, simultaneous hot water needs. The Rheem RTEX-18 would be the next logical step up.
• The home is located in a cold northern climate. The RTEX-18 or RTEX-24 would be the minimum starting point for a whole-home solution.
• The client desires precise, set-and-forget temperature control. A thermostatic model from Rheem or Stiebel Eltron would be more suitable.

Rheem RTEX-13 Alternatives

The RTEX-13 sits in a competitive spot in the market.

Rheem RTEX-11

Rheem RTEX-11 is The direct step-down. The RTEX-11 is cheaper and requires a smaller 50-Amp breaker. However, the RTEX-13's 18% power increase provides a significant boost in flow rate for a modest price increase. For most users trying to decide between the two, the extra power of the RTEX-13 is well worth the small additional cost.

Rheem RTEX-18

Rheem RTEX-18 is The direct step-up. The RTEX-18 is a true mid-range powerhouse at 18kW. It requires a more complex dual-breaker installation (typically 2x40A). It offers a much higher flow rate, making it suitable for larger families and colder climates. If your needs are high, stepping up to the RTEX-18 is the right move.

EcoSmart ECO 11 / ECO 18

EcoSmart ECO 11 / ECO 18 of the EcoSmart are a major competitor. They don't offer a direct 13kW equivalent. Buyers often choose between the ECO 11 (which is less powerful than the RTEX-13) and the ECO 18 (which is more powerful). EcoSmart's main advantage is its limited lifetime warranty. The RTEX-13 fits perfectly in the performance and price gap between these two EcoSmart models.

Rheem RTEX-13 Procurement & Installation

The Rheem RTEX-13 is widely available from major online retailers like Amazon and home improvement stores, making it easy to purchase.

Check Latest Price on Amazon for the Rheem RTEX-13, Also available at The Home Depot and other retailers.

Given the 240V/60A electrical requirement, we strongly recommend hiring a licensed electrician to install the dedicated circuit. A professional plumber can then complete the installation safely and to code.

Rheem RTEX-13 Final Professional Verdict

The Rheem RTEX-13 is a standout performer in the electric tankless water heater market, representing arguably the best power-to-value proposition available. It successfully bridges the gap between smaller, limited-use models and larger, more demanding units. It provides ample power for a huge number of households, all while maintaining a simple design and a manageable installation profile.

It is a reliable, efficient, and cost-effective solution for endless hot water. For small homes, apartments, and high-demand single-bathroom applications, it's a powerful and intelligent choice.

This unit earns a strong professional recommendation. It is a versatile, powerful, and dependable heater that delivers exceptional performance for its price point.

Rheem RTEX-13 FAQ