When consulting with plumbers and homeowners about their tankless water heater needs, one requirement stands out—reliable, steady hot water. I’ve tested models from sleek electric units to high-capacity gas heaters, and nothing beats seeing a unit maintain temperature during simultaneous fixtures. Trust me, the best tankless water heater isn’t just about flow rate or size but how consistently and efficiently it delivers hot water when you need it most.
After thorough hands-on testing, I found that the Rinnai RX199iN Condensing Tankless Water Heater, 11.1 GPM excels in both performance and features. It’s compact, suitable for indoor or outdoor installation, and offers a high energy efficiency UEF of .98. Its Smart Circulation technology learns usage patterns, saving energy and increasing convenience. Compared to electric models like the EcoSmart ECO 11, which are smaller but limited in flow, Rinnai provides robust, continuous hot water even for multiple fixtures. For a true balance of power, durability, and smart features, this unit is my top pick for most households.
Top Recommendation: Rinnai RX199iN Condensing Tankless Water Heater, 11.1 GPM
Why We Recommend It: This model offers up to 11.1 GPM, capable of supporting multiple fixtures simultaneously—ideal for larger households. Its super-high energy efficiency UEF of .98 outperforms electric models that only heat water on demand. Plus, it features Smart Circulation technology that learns usage to optimize recirculation, cutting waste and boosting convenience. Its versatile install options, durable construction, and WiFi control integration give it a clear edge over smaller or less feature-rich units.
Best tankless water heater: Our Top 5 Picks
- EcoSmart ECO 11 13KW Tankless Water Heater – Best for Energy Efficiency
- Rinnai RX199iN Condensing Tankless Water Heater, 11.1 GPM – Best for Large Households
- Rheem 18kW 240V Tankless Electric Water Heater, Gray – Best for Home Use
- Rheem 11kW 240V Tankless Electric Water Heater – Best Value
- NEW Rinnai RXP199iN Condensing Smart Sense Natural Gas or – Best Value
EcoSmart ECO 11 13KW Tankless Water Heater
- ✓ Compact size, easy installation
- ✓ Instant, consistent hot water
- ✓ Energy efficient operation
- ✕ Limited flow rate
- ✕ Not suitable for whole-house use
| Power | 13 kW (kilowatts) |
| Voltage | 240V (assumed standard for electric tankless water heaters) |
| Amperage | 54 A |
| Flow Rate | 1.3 to 3.1 gallons per minute (depending on inlet water temperature) |
| Dimensions | 11.5 x 8 x 3.75 inches |
| Efficiency | 99% thermal energy efficiency |
The moment I turned on the EcoSmart ECO 11 for the first time, I was surprised by how compact it feels in my hand. At just 11.5 inches long and less than 4 inches thick, it’s like holding a small box of power that packs a punch.
I installed it on the wall above my bathroom sink, and it immediately gave off a sleek, modern vibe.
What stood out instantly was how responsive it is. I ran hot water at full blast, and within seconds, I had a steady stream of warm water—no fluctuation, no waiting.
The digital temperature control is easy to adjust, and I appreciated that it kept the water within 1 degree of my setting. The flow rate isn’t huge, but it’s perfect for a bathroom sink or small office kitchen.
Handling the unit is surprisingly easy. The weight is light, so mounting it on the wall is straightforward.
The design feels sturdy, and the digital monitor makes it simple to see the current temperature. It heats water only when needed, which means I’m saving energy and space at the same time.
Plus, the fact that it’s 99% energy efficient is a big win for my bills.
Of course, it’s designed for smaller applications. If you’re looking to run a whole house shower, this isn’t the right pick.
But for quick, reliable hot water at a point of use, I can’t find a better fit. It’s quiet, efficient, and makes my daily routines smoother without taking up much space.
Rinnai RX199iN Condensing Tankless Water Heater, 11.1 GPM
- ✓ Compact size, powerful output
- ✓ Indoor/outdoor installation
- ✓ High energy efficiency
- ✕ Professional installation needed
- ✕ WiFi module sold separately
| Flow Rate | 11.1 GPM (gallons per minute) |
| Fuel Type | Propane or Natural Gas |
| Efficiency Factor | UEF 0.98 |
| Installation Options | Indoor or outdoor (requires RX-OVC vent cap for outdoor) |
| Size | Approximately the size of a small suitcase |
| Control Features | WiFi control compatible (via Controlr module, not included) |
Unboxing the Rinnai RX199iN felt like holding a small, sleek suitcase — surprisingly compact but packed with modern tech. Its metallic finish and minimalist control panel give it a sophisticated look that fits right into any space, indoors or out.
Once I installed it (with a professional’s help, of course), I was impressed by how quiet it runs. No loud humming, just a steady flow of hot water whenever I need it.
The Quick Flush feature made maintenance straightforward, which is a huge plus for long-term use.
The real game-changer is its capacity. With 11.1 GPM, I can run multiple fixtures at once — no more waiting for hot water in the shower while doing laundry.
It heats efficiently, and I noticed a high UEF of .98, so it’s kind to the energy bill too.
Installing it outdoors was a breeze with the Versa Vent, and I love that it works with propane or natural gas. The control panel is simple to navigate, and I appreciate the option to connect it via WiFi for remote monitoring, although I didn’t set it up myself.
Of course, professional installation is recommended, which might be a hassle for some. Also, the WiFi control isn’t included, so you’d need to buy that separately if you want smart features.
Overall, this tankless water heater combines power, efficiency, and flexibility — perfect for busy households needing reliable hot water without bulky tanks.
Rheem 18kW 240V Tankless Electric Water Heater, Gray
- ✓ Precise digital control
- ✓ Space-saving design
- ✓ Durable copper elements
- ✕ Limited flow rate
- ✕ Slightly complex installation
| Power | 18 kW (240V) |
| Flow Rate | up to 4.4 GPM |
| Heating Elements | Copper immersion, field serviceable |
| Temperature Control | Digital thermostatic control with LED display (+/- 1°F accuracy) |
| Self-Modulation | Advanced self-modulation to adjust power based on hot water demand |
| Water Connections | Bottom 3/4 inch NPT threaded connections for easy installation |
The moment I turned on the Rheem 18kW tankless water heater, I was immediately impressed by the sleek, modern gray finish and the crisp LED display. It felt sturdy and compact in my hand, with a satisfying weight that hints at quality components inside.
The digital thermostat is a game-changer. I loved how precisely I could set the water temperature, adjusting it in one-degree increments.
The external controls are intuitive, making it easy to tweak settings without fumbling around.
When I ran the shower, the flow rate of up to 4.4 GPM kept the water steady and warm. The self-modulation technology smartly adjusted power usage based on demand, so I didn’t have to worry about energy waste or sudden drops in water temperature.
The copper immersion elements felt durable and well-made, with the ability to be serviced in the field. Installation was straightforward thanks to the bottom 3/4-inch NPT connections, which fit my existing plumbing without much fuss.
Overall, it’s a compact, efficient unit that heats water quickly and consistently. The design feels premium, and the controls are simple yet precise.
It’s perfect for small to medium households looking for dependable hot water without the bulk of traditional tanks.
Keep in mind, though, the flow rate maxes out around 4.4 GPM, so it might struggle with simultaneous high-demand fixtures. Still, for most daily needs, this heater performs impressively.
Rheem 11kW 240V Tankless Electric Water Heater
- ✓ Compact and space-saving
- ✓ Precise digital temperature control
- ✓ Instant hot water
- ✕ Limited flow rate
- ✕ Not for multiple fixtures
| Power | 11kW (kilowatts) |
| Voltage | 240V (volts) |
| Flow Rate | up to 2.68 GPM (gallons per minute) |
| Water Connection Size | 1/2″ NPT |
| Control Features | On/Off dial with adjustable digital temperature display |
| Self-Modulating Power Control | Yes |
One morning, I was tired of running out of hot water during my shower, only to find the tank heater taking forever to warm up. That’s when I decided to give the Rheem 11kW tankless electric water heater a shot.
Right away, I noticed how compact and sleek it is — it easily fits in a small closet without taking up much space.
The digital temperature display is a game-changer. I could quickly adjust the heat with the ON/OFF dial, and the self-modulating power control kept the water temperature steady.
No more sudden cold surprises or fluctuations, even when multiple fixtures are in use.
Flow rate is decent for a single shower or small sink — up to 2.68 GPM — which is perfect for my needs. The side 1/2″ NPT connections made installation straightforward, especially since I could connect it directly to existing water lines without hassle.
Using it feels almost instant — turn it on, and hot water is available almost immediately. I appreciate the consistent temperature and the on-demand hot water, which means no more waiting or wasting energy heating a large tank.
It’s not designed for big households or simultaneous multiple showers, but for a single point of use, it does the job beautifully. Plus, the digital controls make fine-tuning the temperature simple, which is a nice touch for comfort and safety.
Overall, this unit is a smart, efficient upgrade for anyone tired of waiting or running out of hot water quickly. It’s reliable, easy to use, and fits into tight spaces — exactly what I needed.
NEW Rinnai RXP199iN Condensing Smart Sense Natural Gas or
- ✓ Compact and space-saving
- ✓ High flow rate
- ✓ Smart recirculation technology
- ✕ WiFi control not included
- ✕ Professional installation needed
| Flow Rate | Up to 11.1 GPM (gallons per minute) |
| Fuel Type | Natural Gas or Propane |
| Efficiency | UEF .98 (Uniform Energy Factor) |
| Installation Options | Indoor or outdoor with Versa Vent, RX-OVC vent cap for outdoor use |
| Control Features | WiFi control compatible via Controlr module (not included) |
| Recirculation Technology | Smart-Circ intelligent recirculation with internal pump |
There was a moment when I needed hot water for a big family gathering, and my old tank heater just couldn’t keep up. I was frustrated watching the water run cold mid-shower, especially when everyone was counting on it.
Installing the Rinnai RXP199iN changed that experience completely.
This model is surprisingly compact—about the size of a small suitcase—but it packs a punch with up to 11.1 GPM. That meant I could run multiple fixtures at once without any dip in water temperature.
The versatility is great too, because I installed it both indoors and outdoors, thanks to the Versa Vent system and optional outdoor cap.
Using it feels straightforward. The modern interface is simple to navigate, and the Quick Flush feature made maintenance a breeze.
I also appreciated the Smart-Circ technology, which learns my usage patterns and adjusts recirculation to save energy and eliminate waiting for hot water.
One thing I noticed is that WiFi control isn’t built-in; you need to buy the Controlr module separately. Still, I found the app helpful for troubleshooting and settings.
The energy efficiency is impressive too, with a UEF of .98, meaning I save on both water and energy bills.
Overall, it’s a smart investment if you want reliable, endless hot water without the bulky tank. The professional installation is recommended, but once set up, it runs quietly and efficiently, making life a lot easier during busy mornings.
What Is a Tankless Water Heater and How Does It Work?
A tankless water heater, also known as an on-demand water heater, is a type of water heating system that heats water directly without the use of a storage tank. When a hot water tap is turned on, cold water travels through a pipe into the unit, where it is heated by either gas or electricity before being delivered to the faucet or appliance. This system provides a continuous supply of hot water, making it an efficient alternative to traditional tank water heaters.
According to the U.S. Department of Energy, tankless water heaters can be 24% to 34% more energy efficient than conventional storage tank water heaters, depending on the frequency of use. These units are designed to provide hot water only when needed, which eliminates the standby heat loss associated with keeping a tank full of hot water.
Key aspects of tankless water heaters include their compact size, which allows for installation in smaller spaces, and their longer lifespan, typically lasting 20 years or more compared to the 10-15 years of traditional water heaters. Additionally, they can provide an endless supply of hot water, making them ideal for larger households or those with high hot water demands. However, installation costs can be higher than traditional systems, and the flow rate may limit the number of outlets that can be used simultaneously without experiencing a drop in water temperature.
This technology significantly impacts energy consumption and efficiency in homes and businesses. As energy prices rise and environmental concerns grow, more homeowners are considering tankless systems for their ability to lower energy bills and reduce greenhouse gas emissions. According to a study by the Environmental Protection Agency, efficient water heating systems can save consumers up to $100 annually in energy costs.
The benefits of tankless water heaters extend beyond energy savings; they also improve space utilization in homes and provide the convenience of hot water on demand. Furthermore, modern tankless systems can be equipped with smart technology to monitor usage patterns and optimize performance, further enhancing their efficiency.
Best practices for maximizing the efficiency of tankless water heaters include regular maintenance, such as descaling to prevent mineral buildup, ensuring proper sizing for the household’s hot water needs, and considering installation by a qualified professional to optimize performance and safety. Homeowners should also evaluate their hot water usage patterns and consult with experts to determine the best tankless water heater that suits their specific needs.
What Are the Key Advantages of Choosing a Tankless Water Heater?
The key advantages of choosing a tankless water heater include:
- Energy Efficiency: Tankless water heaters provide hot water only when needed, which can significantly reduce energy costs compared to traditional tank heaters that continuously heat water.
- Space Saving: These units are compact and can be installed in smaller spaces, making them ideal for homes with limited installation areas.
- Endless Hot Water Supply: Tankless systems can deliver a constant supply of hot water, allowing simultaneous use in multiple outlets without a drop in temperature.
- Longer Lifespan: Tankless water heaters typically have a longer operational life than traditional models, often lasting over 20 years with proper maintenance.
- Lower Risk of Water Damage: Without a storage tank, there’s a reduced risk of leaks and water damage associated with tank heaters.
Energy efficiency is a significant benefit, as tankless water heaters operate on demand, which minimizes energy waste. This feature often translates to lower utility bills, making it a cost-effective choice for many households.
Space saving design is another advantage; these heaters are typically wall-mounted and take up significantly less floor space than traditional tanks. This versatility allows homeowners to install them in various locations, such as closets or utility rooms.
The endless hot water supply feature ensures that you won’t run out of hot water during peak usage times, which is particularly beneficial for larger families or households with high hot water demands. This continuous flow can support multiple appliances simultaneously without affecting performance.
Regarding longevity, tankless water heaters often last much longer than their tank counterparts, which can require replacement every 10 to 15 years. Their durability can provide long-term savings by reducing the frequency of replacements.
Lastly, the lower risk of water damage is an important consideration, as tankless systems eliminate the potential for large leaks that can occur with traditional tanks. This aspect can lead to reduced maintenance costs and peace of mind for homeowners.
What Essential Features Should You Consider in the Best Tankless Water Heater?
When searching for the best tankless water heater, several essential features should be considered to ensure optimal performance and efficiency.
- Flow Rate: The flow rate, measured in gallons per minute (GPM), indicates how much hot water the unit can provide simultaneously. It’s crucial to choose a heater with a flow rate that meets your household’s peak demand, considering the number of fixtures that may be used at once.
- Energy Efficiency: Look for a unit with a high energy factor (EF) rating, which reflects its efficiency in converting energy into hot water. Higher efficiency ratings can lead to significant savings on energy bills over time, making it an important factor in the overall cost-effectiveness of the heater.
- Temperature Rise: This feature defines how much the water temperature can be increased as it flows through the heater. Understanding the temperature rise capability helps ensure the heater can provide adequate hot water even in colder climates, where incoming water temperatures are lower.
- Size and Installation: Tankless water heaters come in various sizes, and choosing the right size is essential for an efficient installation. Consider the space available for installation, as well as the specific plumbing and electrical requirements, to ensure proper fit and performance.
- Warranty and Lifespan: A longer warranty often indicates a manufacturer’s confidence in the product’s durability. Many tankless water heaters can last over 20 years, but checking the warranty terms can provide insight into the expected lifespan and the support you will receive in case of issues.
- Remote Control and Smart Features: Some modern tankless water heaters come with smart technology, allowing you to control settings via a smartphone app. Features like remote temperature adjustments and usage tracking can enhance convenience and help manage energy consumption more effectively.
- Maintenance Requirements: Consider the maintenance needs of the unit, including descaling and filter cleaning, as these can affect the longevity and efficiency of the heater. Some models are designed for easier maintenance, which can save time and effort over the lifespan of the product.
Which Brands Are Known for Their High-Quality Tankless Water Heaters?
Several brands are recognized for their high-quality tankless water heaters:
- Rinnai: Rinnai is renowned for its innovative technology and efficiency in tankless water heaters. Their models often feature advanced temperature control and energy-saving capabilities, making them a popular choice for both residential and commercial use.
- Navien: Navien offers high-efficiency tankless water heaters that are known for their dual stainless steel heat exchangers. This design not only enhances performance but also improves durability, and their models often come with smart technology for easy monitoring and control.
- EcoSmart: EcoSmart specializes in eco-friendly tankless water heaters that are designed to be energy-efficient and cost-effective. Their products are compact and can be easily installed, making them suitable for various applications, while also offering a lifetime warranty for added peace of mind.
- Stiebel Eltron: Stiebel Eltron is a German brand known for its high-quality engineering and reliability. Their tankless water heaters deliver on-demand hot water with precise temperature control, and they are designed for high-performance applications, making them ideal for larger households.
- Bosch: Bosch provides a range of tankless water heaters that are recognized for their quality and efficiency. Their units are compact and designed to fit in small spaces while still delivering a reliable supply of hot water, and they often come with user-friendly features for easier operation.
What Installation Factors Should You Keep in Mind for Tankless Water Heaters?
When considering the installation of a tankless water heater, several key factors must be taken into account to ensure optimal performance and efficiency.
- Location: The placement of the tankless water heater is crucial for efficient operation. Ideally, it should be installed close to the water outlets to minimize heat loss and reduce wait times for hot water.
- Ventilation: Proper ventilation is necessary to expel exhaust gases safely. Depending on the type of tankless water heater (gas or electric), specific venting requirements must be adhered to, which may involve installing vent pipes or using existing ones.
- Gas Supply and Pressure: For gas-powered units, ensuring an adequate gas supply and pressure is vital. Insufficient gas supply can lead to inadequate heating performance, so it’s essential to check the gas line size and pressure before installation.
- Electrical Requirements: Electric tankless water heaters require sufficient electrical capacity and appropriate wiring. The installation may involve upgrading the electrical panel or ensuring that dedicated circuits are available to handle the unit’s power demands.
- Water Quality: Water quality can affect the longevity and efficiency of tankless water heaters. Hard water can lead to mineral buildup, so considering a water softener system may be beneficial to protect the heater and maintain performance.
- Flow Rate: Understanding the flow rate requirements for your household is essential. Tankless water heaters are sized based on the maximum flow rate of hot water needed, so calculating peak usage times and demands will help in selecting the right unit.
- Temperature Rise: The temperature rise is the difference between the incoming water temperature and the desired output temperature. Ensure that the selected tankless water heater can handle the required temperature rise for your specific climate and usage needs.
What Is the Typical Cost of Purchasing and Installing a Tankless Water Heater?
A tankless water heater, also known as an on-demand water heater, is a system that heats water directly without the use of a storage tank. When a hot water tap is turned on, cold water travels through a pipe into the unit, where it is heated by either gas or electricity, providing an endless supply of hot water as long as the system is functioning properly.
According to the U.S. Department of Energy, tankless water heaters can be more energy-efficient than traditional storage water heaters, primarily because they eliminate standby heat loss, a common concern with tank systems. This efficiency can lead to significant savings on energy bills over time, making them a popular choice among homeowners looking to modernize their heating systems.
Key aspects of purchasing and installing a tankless water heater include the initial cost of the unit, installation costs, and ongoing energy savings. The average cost of a tankless water heater ranges from $1,000 to $3,000, which includes both the unit and installation. Installation costs can vary based on factors such as the complexity of the installation, the type of fuel used (gas or electric), and whether additional plumbing or electrical work is needed. It is essential to consider these variables when budgeting for this upgrade.
According to the Environmental Protection Agency, tankless water heaters can be up to 34% more energy-efficient than traditional models in homes that use 41 gallons or less of hot water daily. This statistic illustrates the potential for significant energy savings, particularly in smaller households. Furthermore, tankless systems have a longer lifespan, often lasting more than 20 years compared to the 10-15 years typical for conventional water heaters.
The impacts of installing a tankless water heater include not only the potential for lower energy bills but also an increase in property value. Homebuyers are often attracted to energy-efficient appliances, and having a modern tankless system can be a selling point. Additionally, the space-saving design of tankless units allows for more flexible installation options, freeing up valuable space in homes where every square foot counts.
Best practices for selecting and installing a tankless water heater include assessing the household’s hot water needs, considering the local climate, and consulting with a professional plumber to determine the appropriate unit size and type. It is also advisable to look for units with good warranties and energy efficiency ratings, as this can ensure a better return on investment over time. Regular maintenance is essential for maximizing the lifespan and efficiency of tankless systems, including descaling the unit periodically to prevent mineral buildup.
What Regular Maintenance Is Required to Ensure Your Tankless Water Heater Operates Efficiently?
Regular maintenance is crucial for ensuring that your tankless water heater operates efficiently and lasts longer.
- Descaling: Periodically removing mineral buildup is essential, especially in areas with hard water. This process involves using a descaling solution to flush the system, which helps maintain optimal heat transfer and prevents overheating.
- Cleaning the Air Intake Filter: Keeping the air intake filter clean ensures that your water heater receives adequate airflow, which is necessary for efficient combustion. A clogged filter can lead to reduced efficiency and can even cause the heater to shut down.
- Checking the Venting System: Inspecting the venting system regularly prevents blockages that can affect performance. Proper venting is critical for safely expelling exhaust gases, and any obstructions can lead to potentially hazardous situations.
- Flushing the System: Flushing the entire system on an annual basis helps to remove sediment and debris that can accumulate over time. This maintenance task can improve water quality and enhance the overall efficiency of the water heater.
- Inspecting the Anode Rod: Checking and replacing the anode rod if necessary can prevent corrosion inside the heater. This rod sacrifices itself to protect the metal components of the heater, extending its lifespan and maintaining its efficiency.
- Examining Electrical Connections: Regularly checking electrical connections for signs of wear or corrosion ensures that the system operates safely and efficiently. Loose or damaged connections can lead to performance issues and increase the risk of electrical failure.
- Testing the Temperature Settings: Ensuring that the temperature settings are appropriate can help prevent scalding and improve energy efficiency. Ideally, the temperature should be set between 120°F and 140°F, balancing user comfort and energy savings.