A tankless water heater is a good alternative if you need to replace your current water heating system. Unlike traditional tank water heaters, which maintain a reserve of warm water, tankless water heaters heat water only as it flows through the unit. This on-demand heating can potentially lower your utility bills and reduce overall energy consumption.
To help you find the right tankless water heater, we reviewed the top products currently available on Amazon. We considered several key features, including flow rate, power source, and warranty lengths, to come up with our list of recommended picks.
Key Takeaways
- The Rheem RTG gas tankless water heater is the best overall option on our list because of its 7-gallon-per-minute (GPM) flow rate and 160,000 British thermal units (BTU) of power.
- Tankless water heaters typically range from $100–$600 for smaller units and $600–$1,000 or more for heavy-duty models.
- Flow rate capacity and power source are the most critical considerations when selecting a tankless water heater, as electric units have lower flow rates while gas units can supply multiple appliances simultaneously.
Top 5 Tankless Water Heaters
Here’s our list of the best tankless water heaters on the market, based on our research and review of products on Amazon.
- Rheem RTG Gas Tankless Water Heater: Best Overall
- Stiebel Eltron Electric Tankless Water Heater: Best Electric-Powered Water Heater
- EcoSmart Eco Tankless Water Heater: Most Efficient Water Heater
- Rheem RTX-06T Electric Tankless Water Heater: Best for Individual Applications
- Ranein Gas Tankless Water Heater: Best Value
Compare Top-Rated Tankless Water Heaters
Compare the best tankless water heaters based on heat, power, and more in the table below.
| Product | Flowrate | Heat Capacity | Warranty | Power |
|---|---|---|---|---|
Rheem RTG Gas Tankless Water HeaterCheck Price | 7 GPM | 160,000 BTUs | 15-year heat exchanger, 5-year parts, 1-year labor | Natural gas |
Stiebel Eltron Electric Tankless Water HeaterCheck Price | 2.01 GPM | 20 kW | 7-year leakage, 3-year parts | Electric |
EcoSmart Eco Tankless Water HeaterCheck Price | 4.3 GPM | 18 kW | Lifetime warranty on electronics, heat exchanger, and element | Electric |
Rheem RTX-06T Electric Tankless Water HeaterCheck Price | 1.5 GPM | 6.5 kW | 5-year leakage, 1-year parts | Electric |
Ranein Gas Tankless Water HeaterCheck Price | 3.6 GPM | 80,000 BTUs | 2-year manufacturer’s warranty | Gas |
Our Reviews of the Best Tankless Water Heaters
Best Overall
Rheem RTG Gas Tankless Water Heater
Good for: Continuous full-home water heating
We named the Rheem RTG Gas Tankless Water Heater the best natural gas tankless water heater and best overall for a few reasons. The unit delivers up to 7 GPM of continuous hot water, making it ideal for homes with multiple bathrooms. Its compact, wall-mounted design saves valuable floor space while providing consistent, on-demand hot water without the wait.
Pros and Cons of Rheem RTG Gas Tankless Water Heater
- Has an extensive manufacturer’s warranty of 15 years on the heat exchanger
- Provides continuous hot water for multiple fixtures at once
- Saves space with a wall-mounted design
- Has a higher upfront cost than other tankless water heaters we’ve reviewed
- Requires professional installation
Key Features
- Specifics: 7 GPM flowrate and 160,000 BTU heat capacity
- Power: Natural gas
- Coverage area: 2–3 bathrooms
- Warranties: 15 years on the heat exchanger, 5 years on parts, and 1 year on labor
What People Are Saying About The Rheem RTG Gas Tankless Water Heater
Customers report that this Rheem tankless water heater is reliable and integrates smoothly with existing plumbing and venting. Users appreciate its fast heating and consistent hot-water delivery, noting that it also helps reduce gas bills. However, customer feedback is mixed on the noise level, with some finding it excessive. The unit’s reliability is a point of concern, with one customer reporting a motherboard failure.
Best Electric-Powered Water Heater
Stiebel Eltron Electric Tankless Water Heater
Good for: Electric full-home water heating
We named Stiebel’s model as the best electric tankless water heater because of its strong flow rate of up to 2.01 GPM. Additionally, the unit’s intelligent self-modulating technology and compact size ensure ongoing energy savings without requiring venting. The water heater includes a seven-year warranty against leaks and a three year warranty on parts.
Pros and Cons of Stiebel Eltron Electric Tankless Water Heater
- Has an advanced flow control function that keeps water temperature consistent
- Features temperature memory settings
- Provides quiet operation, according to customer reviews
- May cost more than other electric models on the market
- Has a larger footprint than other electric models
Key Features
- Specifics: 2.01 GPM flowrate and 20 kilowatt (kW) heat capacity
- Power: Electric
- Coverage area: Whole house
- Warranties: 7 years against leaks and 3 years on parts
What People Are Saying About The Stiebel Eltron Electric Tankless Water Heater
We found that customers liked the longevity and reliability of this hot water heater. Reviewers on Amazon said the unit worked in their home for over 10 years and dramatically reduced their energy bills. Unsatisfied customers reported that the unit arrived defective, and others said it didn’t work properly on well water.
Most Efficient Water Heater
EcoSmart Eco Tankless Water Heater
Good for: Eco-friendly homes
This EcoSmart tankless water heater delivers up to 4.3 GPM, making it a solid electric unit capable of heating an entire house. We were also impressed by its digital display and temperature control, which allows you to adjust the water temperatures in one degree increments between 80 and 140 degrees Fahrenheit. According to the manufacturer, this unit can save you up to 50% on your water-heating bill thanks to its self-modulating temperature control feature.
Pros and Cons of EcoSmart Eco Tankless Water Heater
- Can help you save up to 50% on water-heating costs
- Includes a lifetime warranty on the unit’s major components
- Offers point-of-use installation to shorten the time it takes for hot water delivery
- Requires professional installation to validate the lifetime warranty
- Some customers have reported poor customer service from the manufacturer
Key Features
- Specifics: 4.3 GPM flowrate and 18 kW heat capacity
- Power: Electric
- Coverage area: Whole house or point-of-use
- Warranties: Lifetime on heat exchanger and heating element and 1 year on electronics
What People Are Saying About The EcoSmart Eco Tankless Water Heater
We noticed several Amazon customers who were pleased with their purchase said that this water heater was easy to install, reliable, and reasonably priced. Unsatisfied customers were disappointed with the manufacturer’s customer service, noting issues when trying to use the warranty.
Best for Individual Applications
Rheem RTX-06T Electric Tankless Water Heater
Good for: Individual bathroom or kitchen sinks
The Rheem RTEX-06T is a compact electric tankless water heater that delivers instant hot water at a precise temperature thanks to its digital thermostatic control. Perfect for point-of-use applications like bathroom sinks or small kitchens, this space-saving unit mounts directly to the fixture to eliminate heat loss and deliver endless hot water on demand.
Pros and Cons of Rheem RTX-06T Electric Tankless Water Heater
- Features a compact, point-of-use design
- Has precise temperature control with the push of a button
- Provides continuous, on-demand hot water
- Has high electrical requirements, like needing a dedicated 40-amp circuit breaker
- Has a lower flow rate than other tankless water heaters on this list
Key Features
- Specifics: 1.5 GPM flowrate and 6.5 kW heat capacity
- Power: Electric
- Coverage area: Single application
- Warranties: 5 years on leaks and 1 year on parts
What People Are Saying About The Rheem RTX-06T Electric Tankless Water Heater
Customers generally find this tankless water heater a good fit for homes, especially those with two bathrooms, noting its compact size as a key advantage over traditional under-sink units. Installation is reportedly easy, and Amazon users frequently talk about significant energy savings exceeding upwards of $100 per month. However, we found inconsistent feedback on water temperature. While some users were satisfied with the heat, others experienced frustrating fluctuations between hot and lukewarm temps.
Best Value
Ranein Gas Tankless Water Heater
Good for: Affordable full-home water heating
This natural gas tankless water heater from Ranein delivers the heating performance of gas units at a price typically comparable to electric units. The unit features a compact, wall-mounted design ideal for small homes, recreational vehicles (RVs), or outdoor applications like camping showers. With easy digital temperature control and a flow rate of up to 3.6 GPM, this unit delivers reliable, on-demand hot water without occupying valuable floor space
Pros and Cons of Ranein Gas Tankless Water Heater
- Activates heating at a lower flowrate of 0.33 GPM
- Costs less than most gas- and electric-powered units with a similar heating output
- Has an ultra-compact design
- Offers a two-year manufacturer’s warranty, which is much shorter than some other units
- Requires professional installation
Key Features
- Specifics: 3.6 GPM flowrate and 80,000 BTU heat capacity
- Power: Natural gas
- Coverage area: Small homes
- Warranties: 2 year manufacturer’s warranty
What People Are Saying About The Ranein Gas Tankless Water Heater
Customers find that this water heater is effective, especially when supplying multiple bathrooms. Users report that the device quickly heats water to the desired temperature and helps reduce energy costs, confirming it’s a worthwhile purchase. However, a few Amazon users have split opinions on durability. Some reviews find the unit long-lasting, while others experienced a failure after only a few months of operation.
Tankless Water Heater Buying Guide
Before you choose a tankless water heater, several key factors can help you narrow your options. First, it’s important to understand the differences between gas and electric heaters. Also, consider whether your home is better suited to a condensing or non-condensing model, and whether you plan to install the unit indoors or outdoors.
From there, examine the heater’s flow rate, which is measured in gallons per minute, and its heat capacity, which is measured in British thermal units or kilowatts. Other important factors to consider include the unit’s ease of installation and warranty coverage. Read our buying guide below for more information on purchasing a tankless water heater.
Tankless Water Heater Flow Rates
Tankless water heaters are rated by the number of gallons of hot water they can deliver per minute, measured in gallons per minute (GPM). Electric water heaters have a lower flow rate than non-condensing gas heaters, and non-condensing gas heaters have a lower flow rate than condensing gas heaters.
When considering your ideal flow rate, determine how many appliances you plan to run simultaneously and how much hot water each one requires. For example, our team found that kitchen faucets require about 0.5 GPM, shower heads require 2.5 GPM, dishwashers require 1 GPM, and washing machines require 1.5 GPM. If you plan to run your dishwasher while showering, your unit requires a minimum flow rate of 3.5 GPM to meet demand.
Types of Power Sources
Tankless water heaters use electricity or gas for power. We measure the heating capacity of gas-powered water heaters in British thermal units (BTU) and of electric water heaters in kilowatts (kW).
- Electric: Electric models connect to your home’s electrical system. As water passes through the unit, a sensor in the heating element activates the burner, and a thermostat raises the water temperature to your desired level. We found that electric water heaters typically cost less than gas-powered units, but may offer less efficiency at heating the water that passes through.
- Gas: Gas-powered water heaters are more efficient, allowing them to heat enough water to run multiple appliances at the same time. Gas units are classified as non-condensing or condensing, depending on whether they use one or two heat exchangers.
Condensing vs. Non-Condensing Units
There are several differences between condensing and non-condensing water heaters, most notably the cost. We break down each type below.
- A non-condensing tankless water heater has one heat exchanger. The exhaust temperature is approximately 300 degrees Fahrenheit, so the unit wastes significant heat that could warm more water. However, this type of gas heater is typically more affordable than its condensing counterpart. Installation also costs less because you can use the same ventilation from your previous gas-powered tank-style water heater.
- A condensing tankless water heater has a second heating system that recirculates the hot exhaust from the first system to preheat additional water. While the initial cost of this water heater is higher than that of a non-condensing unit, you can save money over time due to its lower energy costs.
Tankless Water Heater Installation
Outdoor water heaters offer good options if you don’t have space in your home or can’t install the required ventilation for an indoor gas-powered unit. However, we don’t find outdoor water heaters as efficient in the winter months because they’re directly exposed to cold, which forces them to work harder to heat the water flowing through them.
Electric tankless water heaters are easier to install than gas versions. Because they are small, you can install electric water heaters in more locations. Once you’ve chosen a spot, connect the water heater to your electrical system and water pipes.
If you install a gas-powered water heater inside, it will require ventilation to make sure the byproducts produced by the burning gas don’t remain in your home. Not only does this increase the time and cost to install a tankless water heater, but it also limits where you can place the unit because you need additional space for the vents and ducts.
Note that you may need a licensed technician to install your new tankless water heater to make sure the manufacturer’s warranty stays valid.
Tips for Using a Tankless Water Heater
Once you’ve chosen the best tankless water heater for your home’s needs, the next step is to learn how to use it properly to achieve the best results. When operating a tankless water heater, keep these tips in mind to ensure you’re getting the most value for your money.
Watch the temperature
Adjust the temperature settings of your tankless water heater carefully. Higher temperatures can cause scalding or burning, especially for children or the elderly. Set the water temperature to a safe and comfortable level.
Ensure proper ventilation
Gas-powered tankless water heaters require proper ventilation to operate effectively. Tankless water heaters generate exhaust gases, so it’s important to vent them to the outside of your home to prevent any buildup of harmful gases like carbon monoxide.
Keep the area clear
Avoid storing flammable materials, chemicals, or combustible items near the tankless water heater. Maintain a clear area around the unit for proper airflow and easy access.
Monitor water pressure
Tankless water heaters require sufficient pressure to operate properly. Excessively high water pressure can damage the unit, while low water pressure may result in insufficient hot water. Consider installing a pressure regulator if necessary.
Read the manual
Familiarize yourself with the manufacturer’s instructions and safety guidelines. Each tankless water heater model may have specific requirements and recommendations.
Keep up with maintenance
Depending on the model and type of tankless water heater you choose, we recommend hiring a professional to service the unit once or twice a year. Due to the mineral content or “hard” water in many local water supplies, a professional may need to descale or de-lime your tankless water heater.
FAQs About Tankless Water Heaters
Will I save money with a tankless water heater?
You can save money with a tankless water heater over time because of its higher energy efficiency. Look for an Energy Star-certified product to make sure the unit is efficient. While the cost of a tankless unit is more expensive than the cost of a tank-style unit, you can save money in the long run because it’s more efficient at heating water.
How long will it take my tankless water heater to heat my water?
Most tankless water heaters can heat your water within seconds, according to our team’s testing experience. The short lag you may experience in heating is likely due to the unit’s distance from the faucet tap.
Will my tankless water heater still work if the power goes out?
Since gas water heaters aren’t connected to your electrical system, they should still work if you experience a power outage. Electric heaters will still allow water to flow through them, but their heating element won’t operate without a battery backup.
What are the drawbacks of a tankless water heater?
The drawbacks of tankless water heaters typically include longer wait times for hot water, higher upfront installation costs, and difficulty achieving a lukewarm temperature. Additionally, electric tankless water heaters may not work during a power outage.
Our Methodology
To provide our readers with the best possible tankless water heater recommendations, we rely on several key sources to guide our selection process.
- Initial research: Our research process began by generating a list of tankless water heaters with a significant number of verified buyer reviews and an average customer review rating of 4–5 stars. We reviewed both positive and negative reviews, focusing on insights from both satisfied and critical buyers.
- Expert insights: Through our years of experience, we’ve learned that listening to others is key to producing accurate, well-rounded articles. To complement our in-house expertise, our team reviewed and watched videos from trusted publications and independent testers, spoke with subject-matter experts, and drew insights from reader contributions.
- Final product selection: We then fine-tuned our list by replacing older models with the latest versions and removing discontinued models. From there, we further pared the list by comparing each model’s feature set and selecting the best-in-class options for a range of buyers, budgets, and scenarios.
Why Trust Us?
This Old House has empowered homeowners and DIYers for more than four decades with top-notch home improvement advice through television programs, print media, and digital content. Our team focuses on creating in-depth reviews of products and services. To date, we’ve published over 1,600 reviews of home products, including power tools, outdoor equipment, major appliances, kitchen gadgets, electronics, and more, with a focus on product quality and usefulness for our readers.
