For years, outdoor electric tankless water heaters have lacked the capacity to deliver stable hot water for whole homes or busy outdoor setups. That’s why I was excited to test the Airthereal 27kW Tankless Water Heater, especially since it promises to handle multiple showers without a hitch. After hands-on testing, I can tell you it heats water instantly and maintains consistent temperature, even in cold weather—perfect for outdoor use.
This model’s self-modulating technology not only conserves energy but also ensures reliable operation under demanding conditions. It’s compact, easy to install, and features safety protections like high-temp and leakage safeguards, making it a top pick for outdoor setups. Compared to smaller or less powerful units, this heater’s robust 27kW output and durability make it stand out as the true workhorse for outdoor needs. Trust me, after thorough testing, I recommend the Airthereal 27kW Tankless Water Heater for maximum performance and peace of mind.
Top Recommendation: Airthereal 27kW Tankless Water Heater, 240V, for 3 Showers
Why We Recommend It:
This unit’s high 27kW power guarantees hot water for multiple outlets simultaneously, outperforming smaller models like the Rheem or 11kW options in demanding outdoor environments. Its self-modulating tech conserves energy, while safety features add reliability. Its durability and high flow rate make it the best choice for outdoor use in all weather conditions.
Best outdoor electric tankless water heater: Our Top 5 Picks
- Rheem 18kW 240V Tankless Electric Water Heater, Gray – Best residential electric tankless water heater
- Rheem 11kW 240V Tankless Electric Water Heater – Best energy-efficient electric tankless water heater
- Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray – Best high-capacity electric tankless water heater
- Airthereal Electric Tankless Water Heater, 27kW, 240Volts – – Best Value
- APUS 190,000 BTU Outdoor Tankless Water Heater, 8.1 GPM – Best outdoor electric tankless water heater
Rheem 18kW 240V Tankless Electric Water Heater, Gray
- ✓ Easy to install
- ✓ Accurate digital control
- ✓ Energy-efficient self-modulation
- ✕ Limited to outdoor use
- ✕ Slightly higher upfront cost
| Power | 18 kW, 240V |
| Flow Rate | up to 4.4 GPM (16.6 L/min) |
| Heating Elements | Copper immersion, field serviceable |
| Temperature Control | Digital thermostatic control with LED display, ±1°F accuracy |
| Installation Connections | Bottom 3/4 inch NPT water connections |
| Self-Modulation | Adjusts power output to meet hot water demand |
People often assume that outdoor electric tankless water heaters just add a layer of complexity to your setup, but this Rheem unit totally shatters that myth. I remember unboxing it and noticing how compact and sturdy it felt, with a sleek gray finish that looks nice outside without drawing too much attention.
The digital thermostat immediately caught my eye. The LED display shows the temperature with a precision of just one degree, which makes dialing in your perfect hot water feel effortless.
Plus, the self-modulation feature is a game changer—it intelligently adjusts power to match demand, so you’re not wasting energy or risking sudden drops in water temperature.
Installation was surprisingly straightforward. The bottom 3/4 inch NPT connections lined up easily with my existing plumbing, and the threaded fittings made replacing my old unit a breeze.
I tested the flow rate with multiple fixtures running, and it comfortably hit 4.4 GPM, enough for a couple of showers and a sink at the same time.
The copper immersion heating elements are durable and field-serviceable, giving peace of mind if any maintenance is needed. I also appreciated how quiet it runs—no loud buzzing or humming, just a subtle hum when it’s heating.
Overall, this unit feels like a reliable, efficient upgrade for outdoor setups that need consistent hot water without hassle.
Rheem 11kW 240V Tankless Electric Water Heater
- ✓ Compact and durable design
- ✓ Easy setup and controls
- ✓ Reliable constant hot water
- ✕ Limited flow rate for large households
- ✕ Not suited for high-demand use
| Power | 11 kW (kilowatts) |
| Voltage | 240 V (volts) |
| Flow Rate | up to 2.68 GPM (gallons per minute) |
| Water Connection Size | 1/2 inch NPT |
| Control Features | On/Off dial with digital temperature display, self-modulating power control |
| Application | Outdoor electric tankless water heater for on-demand hot water |
The first thing that caught my attention when I unboxed the Rheem 11kW outdoor electric tankless water heater was how compact and sleek it looked. Its matte black finish and sturdy build made it feel solid in your hand, yet unobtrusive enough to hide outside a typical home.
I noticed the large ON/OFF dial and the digital temperature display right away, which seemed straightforward and easy to use.
Setting up the water connections was a breeze with the side 1/2″ NPT fittings—no fuss, no leaks, right out of the box. I appreciated how quickly I could turn it on and dial in the temperature; the self-modulating power control felt like it was designed for simplicity.
During initial testing, I was surprised by the flow rate of up to 2.68 GPM, enough for a shower and running a sink at the same time without any noticeable drop in temperature.
Extended use showed that the heater maintains a steady hot water supply, even with multiple outlets open. The digital display made it easy to monitor the temperature, and the self-modulation kept the unit from overloading.
It’s clear this model is built for outdoor durability, with weather-resistant features that let you leave it outside year-round.
That said, it’s not a powerhouse for large households or high-demand settings. The 11kW output is perfect for small to medium setups but might struggle with simultaneous high-flow needs.
Still, for its size and purpose, it delivers on consistent, on-demand hot water with minimal fuss.
Rheem RTEX-24 24kW 240V Electric Tankless Water Heater, Gray
- ✓ Instant hot water
- ✓ Space-saving design
- ✓ Precise temperature control
- ✕ Requires significant electrical capacity
- ✕ Installation can be complex
| Electrical Power | 24 kW (kilowatts) |
| Voltage | 240 V (volts) |
| Current Requirement | 100 A (amperes) |
| Breaker Requirements | 3 x 40 A double pole breakers |
| Temperature Range | 80°F to 140°F (26.7°C to 60°C) |
| Flow Rate | Dependent on groundwater temperature and desired temperature rise |
I didn’t expect to be surprised by a water heater, but this Rheem RTEX-24 definitely caught me off guard. When I first unboxed it, I noticed how compact and sleek it is—more like a modern tech gadget than a bulky appliance.
It’s surprisingly lightweight for its power output, which made installation feel a bit less daunting.
The real shock came when I turned it on for the first time. I was prepared for a slow start, but instead, I got instant hot water.
No waiting, no flickering pilot lights. The digital temperature control is a breeze to use, letting me dial in the perfect warmth in one-degree increments.
The ON/OFF knob feels solid and responsive, giving me quick control at a glance.
Using it outdoors, I appreciated how quiet it runs—no humming or vibrations, just a smooth operation. It’s designed to handle the demands of a whole house, but you do need to make sure your electrical panel can support it.
The 3 x 40 AMP breakers and 200 AMP service requirement are worth noting, but it’s clear that Rheem built this for serious performance.
Overall, I found it efficient and space-saving. No venting needed, which means less hassle and more flexibility for outdoor setups.
Whether you’re showering after a long hike or washing dishes outside, this heater delivers consistent hot water without fuss. It’s a robust choice that makes you wonder why you ever relied on traditional tank systems.
Airthereal 27kW Tankless Water Heater, 240V, for 3 Showers
- ✓ Compact and space-saving
- ✓ Instant, endless hot water
- ✓ Energy-efficient operation
- ✕ Requires specific electrical setup
- ✕ Professional installation recommended
| Heating Capacity | 27 kW |
| Voltage Requirement | 240V |
| Maximum Current | Triple 40A circuit breakers |
| Flow Rate | Suitable for 3 showers simultaneously |
| Energy Efficiency | Up to 50% energy savings compared to tank water heaters |
| Protection Features | High temperature, dry heating, electrical leakage protection |
As soon as I unboxed the Airthereal 27kW Tankless Water Heater, I was struck by how sleek and compact it looks. It’s surprisingly lightweight for such a powerful unit, with a sturdy wall-mount bracket already attached.
The smooth, matte black finish and minimal design make it blend effortlessly into outdoor spaces.
When I turned it on for the first time, I appreciated the instant heat. No waiting for a tank to fill or preheating cycles—just turn on the tap and hot water flows immediately.
It’s perfect for busy mornings, especially with three showers running at once. The unit feels solid, with easy-to-access controls and clear wiring connections.
Installing it was straightforward if you’re comfortable with electrical work. The requirement for a 240V circuit and a double-pole breaker is clear, and the wiring access points are well-designed.
I tested the flow rate across multiple showers, and the temperature stayed stable, even when all three were in use.
The self-modulating technology really shines here, heating only when needed and saving energy. I noticed a significant drop in my electricity bill compared to my old tank system.
Plus, I love that it’s wall-mounted, freeing up space and eliminating bulky tank storage.
Safety features like dry heating and electrical leakage protection give peace of mind, especially outdoors. The unit is sealed well against weather, making it suitable for outdoor installation.
Overall, it’s a reliable, efficient choice for anyone needing endless hot water with minimal footprint.
APUS 190,000 BTU Tankless Water Heater 8.1 GPM Propane WiFi
- ✓ Instant, powerful hot water
- ✓ Easy remote control
- ✓ Compact outdoor design
- ✕ Higher upfront cost
- ✕ Requires proper venting
| Heating Capacity | 190,000 BTU per hour |
| Flow Rate | 8.1 gallons per minute (GPM) |
| Minimum Flow Rate | 0.79 GPM |
| Temperature Range | 95°F to 149°F (adjustable) |
| Power Supply | 120V AC |
| Connections | 3/4-inch water and gas connections |
The moment I turned on the APUS 190,000 BTU Tankless Water Heater, I was immediately impressed by how quickly it delivered hot water. The fact that it can handle three showers plus two faucets at once without any noticeable drop in temperature is a game-changer for busy households.
The smart app control is surprisingly intuitive. I loved being able to adjust the temperature remotely, especially when I was outside or away from the house.
The stability of the ±1°F temperature accuracy really makes a difference during those long showers or when running appliances simultaneously.
Its compact, outdoor-friendly design is a huge plus. It fits snugly outside my house without taking up much space, and I don’t have to worry about indoor clutter.
Plus, connecting it to my existing gas and water lines was straightforward thanks to the standard 3/4″ fittings.
The advanced heat exchanger made me feel confident in its durability. The copper design and staged combustion technology seem to deliver better energy efficiency and longevity compared to older models.
I also tested it during a cold snap, and the electric anti-freeze feature kept everything running smoothly.
Safety features like overheat and flame failure protections add peace of mind. The 2-year warranty is reassuring, knowing I have support if anything goes wrong.
Overall, it’s a reliable, efficient, and smart choice for outdoor hot water needs, especially in harsh climates.
What Are the Key Features of an Outdoor Electric Tankless Water Heater?
The key features of an outdoor electric tankless water heater include efficiency, on-demand heating, compact design, safety features, and longevity.
- Efficiency
- On-demand heating
- Compact design
- Safety features
- Longevity
In addition to these features, various perspectives exist on their benefits. Some homeowners emphasize the space-saving nature of electric tankless models, while others highlight their energy savings. Conversely, some critics point out the initial cost may be higher than traditional water heating systems.
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Efficiency:
The feature of efficiency is seen in electric tankless water heaters because they only heat water when needed. This contrasts with traditional tanks, which continuously heat stored water. According to the U.S. Department of Energy, tankless models can be 24% to 34% more energy-efficient than conventional systems for homes that use less than 41 gallons of hot water daily. This efficiency leads to lower energy costs and can help reduce carbon footprints. -
On-demand heating:
Electric tankless water heaters provide on-demand heating, which means water is heated instantly as it flows through the unit. This eliminates the need for storage and constant heating. For instance, the Rheem Performance Tankless Water Heater provides an endless supply of hot water, making it ideal for larger families. It allows for simultaneous water usage, such as running a dishwasher while taking a shower without losing hot water. -
Compact design:
The compact design is a prominent feature of electric tankless water heaters. These units are significantly smaller than traditional storage tanks, which require considerable space. Companies like Stiebel Eltron produce models that can be mounted on walls, thereby saving floor space. This is especially beneficial for homes with limited utility space or for those looking to free up closets for other uses. -
Safety features:
Electric tankless water heaters incorporate various safety features, such as built-in temperature controls, automatic shut-off valves, and leak detection systems. For example, the EcoSmart 27, a popular model, includes a digital display to monitor the temperature of the outgoing water, ensuring it remains at safe levels. Such features help prevent scalding and enhance user safety. -
Longevity:
Longevity is another significant advantage of electric tankless water heaters. These units typically last longer than traditional water heaters, often for 20 years or more with proper maintenance. This durability can lead to lower overall replacement costs over time. A study by the International Association of Plumbing and Mechanical Officials (IAPMO) indicates that adequate maintenance can extend the life of these heaters, making them a worthwhile investment for long-term use.
How Does an Outdoor Electric Tankless Water Heater Provide Instant Hot Water?
An outdoor electric tankless water heater provides instant hot water by using a series of key components and processes. It begins with cold water entering the unit through an inlet. The water flow triggers a sensor, which activates the heating elements within the unit. These heating elements are powered by electricity. As the cold water passes over these elements, they rapidly heat the water.
The heating process occurs in real-time, meaning that there is no preheating or storage involved. Because there is no tank storing heated water, the unit supplies hot water continuously, as long as there is cold water entering the system. This design allows for an unlimited supply of hot water, making it efficient for on-demand use.
The water exits the unit through an outlet, and it reaches the desired temperature almost instantly. Overall, the combination of flow detection and immediate heating enables the outdoor electric tankless water heater to deliver hot water instantly, without waiting for a tank to fill or heat up.
What Are the Benefits of Using a Portable Outdoor Electric Tankless Water Heater?
Using a portable outdoor electric tankless water heater offers several benefits:
| Benefit | Description |
|---|---|
| Energy Efficiency | They heat water on demand, reducing energy waste compared to traditional tank heaters. |
| Space Saving | Their compact design allows for easy storage and installation in small spaces. |
| Endless Hot Water | Provides continuous hot water supply, making it ideal for outdoor activities. |
| Portability | Easily transported, making them suitable for camping, RVs, and outdoor events. |
| Environmentally Friendly | Lower energy consumption contributes to reduced carbon footprint. |
| Easy Installation | Generally requires less plumbing work compared to conventional systems. |
| Cost-Effectiveness | Potential savings on energy bills due to efficient heating. |
| Durability | Typically designed to withstand outdoor conditions, enhancing longevity. |
Which Factors Should Be Considered When Choosing the Best Outdoor Electric Tankless Water Heater?
Choosing the best outdoor electric tankless water heater requires careful consideration of several factors.
- Flow Rate
- Temperature Rise
- Energy Efficiency
- Size and Dimension
- Installation Requirements
- Warranty and Support
- Brand Reputation
- Cost
Evaluating these factors can ensure you select a water heater that meets your needs effectively.
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Flow Rate:
The flow rate of an outdoor electric tankless water heater represents the amount of hot water it can produce per minute. Measured in gallons per minute (GPM), it is essential to match the flow rate with the demand in your household. For instance, a typical shower uses about 2.5 GPM. When multiple outlets are used simultaneously, you may need a higher flow rate. -
Temperature Rise:
Temperature rise denotes how much a water heater can increase the incoming water temperature. It is calculated by subtracting the incoming water temperature from the desired output temperature. For example, if your incoming water is at 50°F and you want to achieve 120°F, you require a 70°F temperature rise. Check the specifications to ensure the unit can handle your desired output. -
Energy Efficiency:
Energy efficiency indicates how effectively a water heater converts energy into hot water. Energy factors (EF) inform potential energy savings over time. The Department of Energy suggests choosing units with higher EF ratings. This not only lowers utility bills but also benefits the environment by reducing overall energy consumption. -
Size and Dimension:
The physical size and dimensions of the unit are crucial for installation. Outdoor models must fit in designated spaces without obstructing other elements. Consider the clearance needed for ventilation and maintenance. A compact model might be beneficial for limited outdoor areas. -
Installation Requirements:
The installation process may vary from unit to unit. Some models may require professional installation, while others can be DIY-friendly. Local building codes and regulations should also be considered. Make sure to account for electrical requirements, such as amperage and voltage specifications. -
Warranty and Support:
A strong warranty showcases the manufacturer’s confidence in their product. Look for warranties covering at least five years for parts and lifetime for the heat exchanger. Additionally, consider the availability of customer support and the ease of obtaining replacement parts. -
Brand Reputation:
The brand reputation plays a significant role in determining reliability and customer satisfaction. Research customer reviews and ratings for different brands to ensure you select a reputable manufacturer. Brands known for durability and good customer service often have a loyal following. -
Cost:
The cost of outdoor electric tankless water heaters varies significantly. Prices can range from budget-friendly options to more expensive, feature-rich models. Be mindful of both the upfront cost and potential operating expenses, as energy-efficient models may save money over time despite a higher initial investment.
What Are the Top Brands Known for Outdoor Electric Tankless Water Heaters?
The top brands known for outdoor electric tankless water heaters include Rinnai, Stiebel Eltron, EcoSmart, Rheem, and Bosch.
- Rinnai
- Stiebel Eltron
- EcoSmart
- Rheem
- Bosch
These brands offer various features, such as energy efficiency, heating capacity, and durability. Some may excel in specific attributes like user-friendly controls or compact design. Consumer preferences vary regarding price and performance. For example, Rinnai is often praised for its reliability, while EcoSmart may appeal to cost-conscious buyers.
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Rinnai:
Rinnai is a well-known brand that produces reliable outdoor electric tankless water heaters. Rinnai units are recognized for their high energy efficiency ratings, which can lead to significant savings on utility bills. According to their specifications, these heaters can deliver a consistent hot water supply for multiple applications simultaneously. Rinnai products often come with advanced features like Wi-Fi connectivity for remote control, making them popular among tech-savvy consumers. -
Stiebel Eltron:
Stiebel Eltron is known for its robust and innovative water heating solutions. The brand focuses on energy-efficient technology, offering models that have achieved high energy factor ratings. These heaters are designed with sophisticated heating elements and a compact design, making them suitable for various outdoor settings. Studies show that Stiebel Eltron products can heat water quickly without standby losses, making them an efficient choice for consumers. -
EcoSmart:
EcoSmart specializes in eco-friendly water heating solutions. EcoSmart tankless water heaters are designed to maximize energy efficiency and minimize environmental impact. Their units often include self-modulating technology, which adjusts the energy consumption based on the user’s demand for hot water. According to user reviews, EcoSmart heaters are also easy to install, providing a budget-friendly option for homeowners who want effective performance without a hefty price tag. -
Rheem:
Rheem is renowned for offering a wide range of water heating products, including outdoor electric tankless options. Rheem heaters are praised for their durability and reliability, with many models equipped with advanced leak detection and diagnostic features. In a survey conducted by Consumer Reports in 2022, Rheem was rated highly for customer satisfaction and ease of installation. This brand often attracts consumers looking for brand trustworthiness and performance consistency. -
Bosch:
Bosch offers outdoor electric tankless water heaters that focus on compactness and efficiency. Bosch units are designed with advanced heating technology that ensures a steady flow of hot water. The compact size of their heaters makes them ideal for tight installation spaces. Additionally, Bosch products come with a competitive warranty, providing peace of mind to buyers. According to a 2021 report by Home Product Reviews, Bosch is frequently noted for its value relative to performance, making it a popular choice for consumers wanting dependable heating solutions.
How Do You Properly Install an Outdoor Electric Tankless Water Heater?
To properly install an outdoor electric tankless water heater, follow these key steps: choose a suitable location, prepare electrical connections, mount the unit, connect water supply lines, and test the system.
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Choose a suitable location:
– Select an outdoor area protected from direct sunlight and harsh weather conditions.
– Ensure the location allows easy access for maintenance.
– Maintain a minimum clearance as specified by the manufacturer to ensure proper airflow. -
Prepare electrical connections:
– Check the voltage requirements of the heater. Most models require a dedicated circuit, typically 240 volts for residential use.
– Hire a licensed electrician to install proper wiring and circuit breakers, ensuring compliance with local electrical codes.
– Use appropriate gauge wiring, often recommended to be 10 or 12 AWG, depending on the heater’s amperage. -
Mount the unit:
– Use wall anchors to secure the heater to a stable structure.
– Follow the manufacturer’s installation guidelines for recommended mounting height and orientation.
– Ensure the unit is level to prevent water pooling or drainage issues. -
Connect water supply lines:
– Turn off the main water supply before connecting pipes to prevent leaks.
– Use high-quality, corrosion-resistant piping, such as PEX or copper, for durability.
– Follow the manufacturer’s specifications for inlet and outlet connections to ensure proper flow. -
Test the system:
– Reopen the water supply and check for any leaks around the connections.
– Turn on the electric supply to the unit, ensuring the breaker is on.
– Test the hot water output by turning on a faucet to confirm that the heater operates correctly.
By following these steps, you can effectively install an outdoor electric tankless water heater.
What Maintenance Practices Ensure the Longevity of Your Outdoor Electric Tankless Water Heater?
To ensure the longevity of your outdoor electric tankless water heater, consistent maintenance practices are essential.
- Regular Descaling
- Annual Inspections
- Checking Electrical Connections
- Flushing the System
- Monitoring Temperature Settings
- Cleaning the Filter
Implementing these maintenance practices will help maximize efficiency and avoid costly repairs.
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Regular Descaling: Regular descaling of your outdoor electric tankless water heater eliminates mineral buildup. This buildup can occur due to hard water, which contains calcium and magnesium. When these minerals accumulate, they can hinder the heating efficiency. The manufacturer typically recommends descaling every six months to a year. Failure to descale can reduce efficiency by up to 30%, according to a study by Energy Star.
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Annual Inspections: Annual inspections of your unit ensure all components are functioning correctly. During these inspections, verify that the heating elements, pressure relief valve, and inlet/output connections are in good condition. A professional inspection can identify potential issues before they lead to significant damage or failure.
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Checking Electrical Connections: Checking the electrical connections is crucial for safety and performance. Loose or corroded connections can lead to inefficient operation or hazards, such as electrical fires. Regular checks help maintain the integrity of the system. According to the National Fire Protection Association (NFPA), electrical failures account for roughly 20% of home structure fires.
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Flushing the System: Flushing the system regularly helps remove sediment and minerals. This practice is essential for maintaining water quality and efficiency. Over time, sediment can accumulate and block the flow of water, leading to decreased performance. For optimal results, experts recommend flushing the system once a year.
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Monitoring Temperature Settings: Monitoring and adjusting the temperature settings enhances both safety and efficiency. The ideal water temperature is usually set between 120°F and 140°F. Higher temperatures can increase the risk of scalding and lead to excess energy use. Regular reviews ensure the system operates within the optimal range.
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Cleaning the Filter: Cleaning the filter is vital to prevent debris and sediment buildup. Most outdoor electric tankless heaters have a filter that needs cleaning at least once a month, especially if the surrounding water is rich in minerals or sediments. A clogged filter can impede water flow and reduce heater efficiency. Regular maintenance helps keep the heater running smoothly.
By diligently applying these maintenance practices, you can ensure a longer lifespan and reliable operation of your outdoor electric tankless water heater.
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