Best Whole House Tankless Water Heater in 2025: Tested and Reviewed

When it comes to modernizing your home’s hot water system, a whole house tankless water heater is a game-changer. Gone are the days of waiting for a bulky tank to heat up, or dealing with cold showers when you least expect it. Tankless water heaters offer an endless supply of hot water on demand, and they do so more efficiently than traditional systems. But with so many options available in the market, how do you choose the best one for your home? In this guide, we’ve tested and reviewed the top whole house tankless water heaters to help you find the perfect fit for your needs.

List of the Best Whole House Tankless Water Heater:

Check out the detailed reviews below.

1. Rinnai RX199iN Tankless Water Heater

The Rinnai RX199iN Condensing Smart Sense Tankless Water Heater is a high-performance model designed for both residential and commercial use. Powered by either natural gas or propane, this unit delivers up to 11.1 GPM, making it ideal for homes with moderate to high hot water demands. With an impressive 199,000 BTU rating, it ensures a consistent and reliable supply of hot water, even when multiple fixtures are used simultaneously. Its compact design, similar in size to a small suitcase, allows for easy installation in both indoor and outdoor environments, offering flexibility to homeowners.

Efficiency is a key feature of the RX199iN, with a UEF (Uniform Energy Factor) of 0.98, placing it among the most energy-efficient models in the market. The condensing technology extracts additional heat from exhaust gases, improving performance and reducing energy consumption. The innovative Smart Sense gas control system adapts to the household’s needs, optimizing performance while minimizing waste. Additionally, the Quick Flush feature simplifies maintenance, extending the unit’s lifespan.

Key Features, Pros, and Cons

Key Features:

• Up to 11.1 GPM, ideal for larger households.
• High efficiency with a UEF of 0.98.
• Compact design, easy to install indoors or outdoors.
• Smart Sense gas control system for optimized performance.
• Quick Flush feature for simplified maintenance.

Pros:

• Provides ample hot water for multiple fixtures simultaneously.
• Energy-efficient with a high UEF of 0.98, reducing energy costs.
• Space-saving, compact design fits into tight spaces.
• Versatile, supports both propane and natural gas options.
• Quick Flush function makes maintenance easy.

Cons:

• Wi-Fi module for remote control is sold separately.

2. Rheem RTGH-95DVLN-3 Tankless Water Heater

The Rheem RTGH-95DVLN-3 RTGH Series 9.5 GPM Natural Gas Tankless Water Heater is a highly efficient solution for continuous hot water in residential applications. With a powerful 199,900 BTU rating, this unit offers a flow rate of up to 9.5 GPM, making it suitable for moderate to large homes. The RTGH Series features a compact, modern design that saves valuable space, with an easy-to-install wall-mount bracket and minimal clearance requirements. This model is designed to be energy-efficient, using up to 34% less energy than traditional 50-gallon tank heaters, and reducing greenhouse gas emissions by up to 65%.

The RTGH-95DVLN-3 is equipped with advanced features such as Hot Start Programming, which eliminates cold water bursts during consecutive uses, ensuring a consistent supply of hot water. The exclusive Water Saving Setting helps reduce water waste, saving up to 1,100 gallons annually. It also offers a long lifespan, with the heat exchanger covered under a 15-year warranty. The unit operates quietly and offers adjustable temperature settings between 100°F and 140°F.

Key Features, Pros, and Cons

Key Features:

• Flow rate of 9.5 GPM, suitable for moderate to large homes.
• Energy-efficient, using up to 34% less energy than traditional tank heaters.
• Compact design with easy installation and minimal clearance.
• Hot Start Programming eliminates cold water bursts between uses.
• Water Saving Setting reduces waste by saving up to 1,100 gallons of water annually.

Pros:

• High flow rate ensures continuous hot water for multiple fixtures.
• Energy-efficient, reducing energy bills and greenhouse gas emissions.
• Compact and space-saving design.
• Advanced features like Hot Start Programming enhance user comfort.
• Durable with a 15-year warranty on the heat exchanger.

Cons:

• Some users report noise during operation.

3. Rheem RTEX-27 240V Tankless Water Heater

The Rheem RTEX-27 240V Tankless Water Heater is a powerful and energy-efficient solution for residential hot water needs. With a 27,000-watt heating capacity, this model provides consistent and reliable hot water, making it ideal for medium to large households. Its advanced self-modulation technology adjusts the power based on the water demand, ensuring optimal energy use while providing hot water on demand. The external digital thermostatic control with LED display allows precise temperature adjustments with a +/-1 degree accuracy, ensuring a comfortable and consistent experience.

Equipped with durable copper immersion heating elements, the RTEX-27 offers long-lasting performance, and these elements are field serviceable for ease of maintenance. The unit features a simple installation process, with 3/4-inch NPT water connections that allow for a straightforward setup. However, some customers have noted mixed feedback, with some reporting excellent performance while others have experienced issues with water supply and quality.

Key Features, Pros, and Cons

Key Features:

• 27,000-watt heating capacity provides ample hot water for medium to large homes.
• External digital thermostatic control with LED display for precise temperature settings.
• Self-modulation adjusts power to meet water demand, improving energy efficiency.
• Durable copper immersion heating elements that are field serviceable.
• Easy installation with 3/4-inch NPT water connections.

Pros:

• Provides consistent hot water on demand.
• High energy efficiency with self-modulation technology.
• Easy installation with simple connections.
• Durable copper heating elements for long-lasting performance.
• Accurate temperature control (+/-1 degree).

Cons:

• Mixed customer feedback on water supply consistency.

4. Rheem RTGH-95DVELP-3 Tankless Water Heater

The Rheem RTGH-95DVELP-3 Super High Efficiency Condensing Indoor Tankless Liquid Propane Water Heater is designed for homes seeking continuous hot water with maximum energy efficiency. With a flow rate of 9.5 GPM, this unit is capable of supplying hot water to multiple fixtures simultaneously, making it ideal for medium to large homes. The unit’s high-efficiency condensing technology ensures that it uses less energy, as it only operates when needed, reducing energy bills while providing a consistent supply of hot water.

One standout feature is the built-in EcoNet Wi-Fi technology, which allows users to control temperature, track energy usage, and receive maintenance alerts directly from a mobile device. Additionally, Hot-Start programming ensures the unit is always ready to deliver hot water without the typical cold water bursts found with traditional systems. The LeakGuard leak detection and prevention system provides an added layer of protection, identifying and preventing leaks before they cause damage. The compact design makes installation easy, especially in tight spaces.

Key Features, Pros, and Cons

Key Features:

• 9.5 GPM flow rate for ample hot water across multiple fixtures.
• EcoNet Wi-Fi technology allows remote control and monitoring via mobile devices.
• Hot-Start programming prevents cold water bursts between uses.
• LeakGuard leak detection prevents costly water damage.
• Compact design allows for flexible installation in small spaces.

Pros:

• Efficient energy use, reducing energy costs.
• Wi-Fi control for convenience and monitoring.
• Continuous hot water for large homes or multiple users.
• Advanced leak detection adds peace of mind.
• Easy installation with minimal space required.

Cons:

• Mixed functionality feedback, with some users reporting malfunctions.

5. Stiebel Eltron 239223 Tankless Water Heater

The Stiebel Eltron Tempra 29 Plus Tankless Water Heater offers on-demand hot water with advanced features for optimal performance and energy efficiency. With a powerful 28.8 kW heating capacity, this unit delivers continuous hot water for medium to large households. Its innovative Advanced Flow Control technology ensures consistent water temperature by slightly reducing flow if hot water demand exceeds the unit’s capacity, preventing interruptions during use. This electric model operates without venting, making it ideal for homes where space is a concern. The sleek design and compact size allow for easy installation and save valuable space compared to traditional tank water heaters.

The Tempra 29 Plus is highly energy-efficient, consuming 15-20% less energy than conventional electric tank models, with even greater savings possible depending on usage habits. It does not store hot water, which eliminates standby heat loss, a common problem with tank systems. With a digital LED display and two temperature memory presets, users can easily customize settings for comfort. However, it requires a hard-wired 240V or 208V electric service, along with proper breaker and wiring installations, making professional installation essential.

Key Features, Pros, and Cons

Key Features:

• Delivers on-demand hot water without storing it, reducing energy waste.
• Advanced Flow Control ensures stable water temperature even during high demand.
• Digital LED display with two memory presets for convenience.
• Saves up to 20% more energy than traditional tank models.
• Compact design frees up space and requires no venting.

Pros:

• Continuous and unlimited hot water on demand.
• High energy efficiency with significant cost savings.
• Simple installation with a sleek, space-saving design.
• Advanced technology ensures consistent temperature control.
• No venting required, making it ideal for small spaces.

Cons:

• Requires a hard-wired 240V or 208V service and professional installation.

How to Choose the Best Whole House Tankless Water Heater?

When it comes to providing hot water for your home, a tankless water heater offers unmatched efficiency and reliability. Gone are the days of bulky water heaters that take up valuable space and constantly run out of hot water. A tankless water heater provides endless hot water on demand, while also saving energy and reducing costs. But with so many options available, how do you choose the best one for your home?

Why Choose a Tankless Water Heater?

Before diving into the specifics of choosing the right tankless model, it’s important to understand why many homeowners are switching to tankless systems in the first place. Traditional tank water heaters can waste energy by continuously heating water to maintain a set temperature. In contrast, a tankless water heater heats water only when you need it, which can result in significant energy savings. Additionally, these systems are more compact and can last much longer than traditional tank heaters.

Step 1: Assess Your Hot Water Needs

The first thing you need to do when choosing a tankless water heater is determine your household’s hot water demand. This step is critical to ensure you select a system that will meet your needs without underperforming.

Consider the number of people in your household: The more people you have, the higher your hot water usage will be. Larger families typically need a more powerful unit that can handle multiple showers, laundry loads, and dishwashing at once.

Identify peak usage times: If everyone in your house tends to take showers in the morning, or you often run the dishwasher while someone else showers, you’ll need a system that can handle this simultaneous demand.

Check the flow rate: Tankless water heaters are rated by their flow rate, usually measured in gallons per minute (GPM). A standard shower uses about 2 GPM, while a dishwasher or washing machine may use around 1.5 GPM. You’ll want to calculate how many fixtures will be in use at once and choose a system with a sufficient GPM rating.

Step 2: Understand Your Home’s Power Source

Tankless water heaters come in two primary types: electric and gas. Both have their advantages, but choosing the right one depends largely on your home’s infrastructure and your personal preferences.

Gas-powered models: If you have natural gas lines already installed in your home, a gas-powered tankless water heater might be the best choice. These models tend to provide higher flow rates, making them ideal for larger households with high demand for hot water. They also work well in colder climates, where electric models might struggle to maintain desired temperatures.

Electric-powered models: If you don’t have access to natural gas or want a more eco-friendly option, electric tankless water heaters are a great alternative. They are typically more energy-efficient and cost less to install. However, they may not be able to handle large households with multiple water demands simultaneously, especially in colder regions where incoming water temperature is lower.

Step 3: Choose the Right Size

Choosing the correct size is essential to ensuring that your tankless water heater performs optimally. If you buy one that is too small, it may not be able to keep up with your hot water demands, while an oversized unit may lead to wasted energy and unnecessary expense.

Flow rate and temperature rise: These two factors will help you determine the size of the unit you need. The flow rate refers to how much water the heater can supply per minute, while the temperature rise refers to how much the unit can raise the water’s temperature based on the incoming water temperature. In warmer climates, the temperature rise requirement may be lower, while colder climates may require more powerful units to achieve the desired temperature.

Capacity considerations: For a family of four, you’ll likely need a unit with a flow rate of at least 6-8 GPM. For larger homes or families, consider higher GPM models, especially if you anticipate running multiple fixtures at once.

Step 4: Review Energy Efficiency

One of the biggest benefits of a tankless water heater is its energy efficiency. But how can you ensure you’re getting the most energy-efficient option? Look for models with high Energy Factor (EF) ratings. The higher the EF, the more efficiently the heater uses electricity or gas.

Additionally, many tankless water heaters are designed to be low-flow, meaning they use less water without sacrificing performance. Be sure to choose a model that boasts both energy efficiency and water conservation features, so you can save money on your utility bills.

Step 5: Research the Features and Brand Reputation

Not all tankless water heaters are created equal, so it’s essential to do your homework and research different brands and their offerings.

User-friendly controls: Modern tankless water heaters often come with digital controls that make it easy to adjust the temperature and monitor the system’s performance. Some models also offer Wi-Fi connectivity, allowing you to control your water heater remotely through your smartphone.

Warranty and customer support: Look for a model with a solid warranty (at least 10 years for the heat exchanger). This ensures that you’ll have peace of mind in case something goes wrong. Additionally, choose a reputable brand known for reliable customer service.

Step 6: Installation Considerations

Installing a tankless water heater can be more complicated than replacing a traditional tank model. For gas-powered units, the installation may require venting and gas line adjustments, while electric units may require an upgraded electrical panel. Be sure to consult a professional plumber or electrician to determine the scope of the installation.

Consider the location: Tankless water heaters can be installed indoors or outdoors, depending on your space and climate. Outdoor units tend to cost less to install, as they don’t require the same level of protection from the elements as indoor models.

Step 7: Budget and Long-Term Savings

While tankless water heaters are often more expensive upfront compared to traditional tank models, the long-term savings can make them a more cost-effective option. In addition to lower energy bills, these units also tend to last longer, with some lasting up to 20 years or more.

Installation costs: Remember that the installation of a tankless water heater may be more expensive than installing a traditional unit, especially if upgrades to your gas lines or electrical system are necessary. However, these costs will be offset over time by the energy savings.

Frequently Asked Questions When Selecting the Best Whole House Tankless Water Heater

What is a whole house tankless water heater?

A whole house tankless water heater is a type of water heating system that provides hot water on demand, directly to multiple outlets throughout your home, without the need for a storage tank. These units heat water as it passes through, ensuring you never run out of hot water. They are designed to handle the hot water demands of an entire home, offering energy-efficient solutions for families or households with high water usage.

How does a tankless water heater work?

A tankless water heater works by heating water only when it’s needed. When you turn on a hot water tap, cold water flows through the unit. A heating element (either electric or gas) then heats the water as it passes through, delivering hot water to your fixtures in real-time. This process eliminates the need for a storage tank, making the system more efficient and space-saving compared to traditional water heaters.

What are the benefits of a whole house tankless water heater?

There are several key benefits of choosing a tankless water heater for your home:

• Endless Hot Water: You won’t run out of hot water, even if multiple fixtures are in use simultaneously.
• Energy Efficiency: Tankless units only heat water when it’s needed, reducing energy consumption and lowering utility bills.
• Space Saving: Without the need for a bulky storage tank, these units are compact and can be installed in smaller spaces.
• Longer Lifespan: Tankless water heaters typically last 20+ years, much longer than traditional tank models.
• Environmental Impact: Their energy-efficient nature can reduce your household’s carbon footprint.

How do I choose the right size for my tankless water heater?

Choosing the right size depends on two key factors:

• Flow Rate: This is measured in gallons per minute (GPM) and determines how much water the unit can heat at once. A standard shower uses about 2 GPM, and you need to consider the simultaneous use of showers, faucets, and appliances.
• Temperature Rise: This refers to the increase in water temperature required based on the incoming water temperature. In colder climates, you’ll need a unit with a higher temperature rise.

To calculate the required flow rate, add up the GPMs of the fixtures you’ll be using at the same time (e.g., two showers at 2 GPM each, plus a dishwasher at 1.5 GPM).

Should I choose an electric or gas tankless water heater?

The choice between electric and gas tankless water heaters depends on your home’s setup:

• Electric: These units are typically easier and less expensive to install, making them ideal for smaller households or homes without access to natural gas. However, they have a lower flow rate, which may not be ideal for larger homes.
• Gas: Gas-powered tankless water heaters tend to have higher flow rates and are better suited for larger homes or households with higher hot water demand. They also perform better in colder climates where the incoming water temperature is lower. However, gas models often require more complex installation due to venting and gas line requirements.

What is the lifespan of a whole house tankless water heater?

Tankless water heaters typically last much longer than traditional tank models. With proper maintenance, these units can last between 20 to 30 years, depending on the quality of the unit and usage. In comparison, traditional water heaters usually last around 10-15 years. Regular maintenance, such as descaling and flushing the system, can extend the lifespan of your tankless water heater.

What is the cost of installing a whole house tankless water heater?

The cost of installing a whole house tankless water heater can vary depending on several factors, including the type of system (gas or electric), the complexity of installation (e.g., new gas lines or electrical upgrades), and the brand you choose. On average, installation costs can range from $1,000 to $3,000. Gas models typically have higher installation costs due to venting and gas line requirements, while electric models tend to be less expensive to install.

Do I need professional installation for a tankless water heater?

Yes, it is highly recommended to have a professional plumber or electrician install your tankless water heater. While some homeowners with technical knowledge may attempt the installation themselves, these units require specific considerations for safety, efficiency, and code compliance. A professional installer will ensure proper sizing, ventilation, and connection to water, gas, or electrical lines, preventing issues down the road.

How much energy can I save with a tankless water heater?

Tankless water heaters are more energy-efficient than traditional tank models because they only heat water on demand. You can expect energy savings of up to 30% or more compared to a conventional water heater. However, savings will depend on your household’s water usage and the type of tankless model you choose. Over time, the reduced energy consumption will lead to lower utility bills, making it a smart investment.

Can a whole house tankless water heater handle multiple fixtures at once?

Yes, a whole house tankless water heater is designed to handle multiple fixtures simultaneously. However, its ability to do so depends on the unit’s flow rate (GPM) and the temperature rise it can achieve. If your household has high water demands (e.g., multiple showers running at once), make sure to choose a unit with a higher flow rate. For larger homes or families, a more powerful unit may be necessary to ensure hot water is supplied to all fixtures without interruption.

How often do I need to maintain a tankless water heater?

Regular maintenance is essential to keep your tankless water heater running efficiently. It’s recommended to flush the unit every 12 months to remove any mineral buildup, especially if you live in an area with hard water. You should also check the filters and vents, as well as inspect the unit for any signs of wear or damage. In addition to flushing, it’s important to schedule a professional maintenance check every 1-2 years to ensure optimal performance.

What are some top brands for whole house tankless water heaters?

Several well-known and reliable brands manufacture top-quality whole house tankless water heaters. Some of the best options include:

• Rinnai: Known for their energy-efficient, durable, and high-performing models.
• Navien: Offers both gas and hybrid models with excellent energy efficiency.
• Tankless: Specializes in a variety of reliable, energy-efficient systems for all home sizes.
• EcoSmart: A popular brand offering electric tankless systems with smart technology for energy savings.
• Noritz: Known for their durable, high-efficiency gas-powered models with excellent warranties.

Conclusion

Choosing the best whole house tankless water heater can be overwhelming, but with the right information, you can make an informed decision that fits both your household’s needs and budget. From energy savings to the endless supply of hot water, a tankless water heater is a smart investment for any home.

Enjoyed this guide of the best whole house tankless water heater? Then be sured to check out our other heaters reviews.

• Best Electric Tankless Water Heater
• Best Propane Tankless Water Heater
• Best Natural Gas Tankless Water Heater
• Best 7500-Watt Electric Garage Heater
• Best 10,000-Watt Electric Garage Heater
• Best Heat Pump for Inground Pool
• Best Heat Pump for Above-Ground Pool
• Best RV Tankless Water Heater