Updated:10/08/2026
Rank 1-17 of the best tankless water heaters
Our recommendation Price Customer rating
1. Comparison winner
Rheem RTG-70XLN-3 Outdoor Tankless Gas Water Heater
Rheem RTG-70XLN-3 Outdoor Tankless Gas Water Heater
Available immediately
free shipping
  • high efficiency water heater reduces energy costs by operating only when needed
  • provides continuous hot water for multiple applications throughout the house
  • features hot-start programming to maintain water temperature and prevent cold water bursts
Our rating
9,8
very good
2. Best value
FOGATTI InstaShower 8 Plus RV Tankless Water Heater
FOGATTI InstaShower 8 Plus RV Tankless Water Heater
Available immediately
free shipping
  • tankless design saves energy by only using burners when hot water is needed
  • provides a water flow rate of 2.9 gallons per minute
  • allows temperature control from 95°F to 123°F using a remote controller
Our rating
9,8
very good
Rinnai RX199iN Tankless Water Heater
Rinnai RX199iN Tankless Water Heater
Available immediately
free shipping
  • ultra-high energy efficiency factor of 0.98
  • provides a flow rate of up to 11.1 gallons per minute
  • easy-to-use temperature control interface with Quick Flush feature
Our rating
9,8
very good
GIRARD Tankless RV Water Heater 2022107534
GIRARD Tankless RV Water Heater 2022107534
Available in a few days
free shipping
  • high energy efficiency, consuming half the LP gas compared to traditional six-gallon tank water heaters
  • provides continuous hot water with a flow rate driven by an onboard microprocessor for optimal performance
  • regulates water temperature between 95 to 124°F to maintain a steady and safe water flow
Our rating
9,8
very good
5. Bestseller
EcoSmart ECO 27 Electric Tankless Water Heater 27kW
EcoSmart ECO 27 Electric Tankless Water Heater 27kW
Available immediately
free shipping
  • energy efficiency of 99.8%
  • provides between 2.7 and 6.5 gallons per minute depending on inlet water temperature
  • digital temperature control for precise temperature setting
Our rating
9,8
very good
100+ purchases last month
Rheem 18kW Tankless Electric Water Heater
Rheem 18kW Tankless Electric Water Heater
Available immediately
free shipping
  • energy-efficient tankless electric water heater heats water only when needed
  • flow rate up to 4.4 gallons per minute
  • digital control with LED display and precise temperature regulation
Our rating
9,8
very good
100+ purchases last month
Ranein 2025 GEN II Tankless Water Heater
Ranein 2025 GEN II Tankless Water Heater
Available immediately
free shipping
  • heats water on demand to eliminate standby energy waste and reduce utility costs
  • supports a maximum flow rate of 8.5 gallons per minute, meeting continuous household hot water needs for up to 6 taps
  • maintains stable water temperature with auto-adjusting flow and heat to prevent sudden changes
Our rating
9,6
very good
Stiebel Eltron Tempra 29 Plus Tankless Water Heater
Stiebel Eltron Tempra 29 Plus Tankless Water Heater
Available immediately
free shipping
  • 99% energy efficiency for up to 34% savings on water heating costs
  • continuous and unlimited hot water supply, suitable for multiple showers or bathrooms
  • automatic temperature control maintains desired temperatures during high demand
Our rating
9,6
very good
50+ purchases last month
EcoSmart ECO 18 Electric Tankless Water Heater
EcoSmart ECO 18 Electric Tankless Water Heater
Available immediately
free shipping
  • capable of heating over 2.5 gallons per minute
  • digital temperature control for setting temperature in 1-degree increments
  • compact design allows installation in limited spaces
Our rating
9,6
very good
Rheem RTEX-13 Tankless Water Heater
Rheem RTEX-13 Tankless Water Heater
Available immediately
free shipping
  • 99.8% energy efficiency for cost-effective operation
  • up to 3.17 gallons per minute flow rate for consistent water pressure
  • temperature control adjustable in 1 degree fahrenheit increments for precise hot water settings
Our rating
9,6
very good
50+ purchases last month
Rheem RTEX-24 Electric Tankless Water Heater
Rheem RTEX-24 Electric Tankless Water Heater
Available immediately
free shipping
  • tankless electric design offers energy-efficient operation eliminating standby heat loss
  • flow rate of 5.9 gallons per minute for providing continuous hot water
  • temperature control allows adjustments in 1-degree increments from 80 to 140 degrees fahrenheit
Our rating
9,5
very good
50+ purchases last month
Rheem 11kW Electric Water Heater
Rheem 11kW Electric Water Heater
Available immediately
free shipping
  • energy efficient due to self-modulating power control
  • flow rate of up to 2.68 gallons per minute
  • digital temperature control with adjustable display
Our rating
9,5
very good
100+ purchases last month
EcoSmart ECO 11 Tankless Water Heater
EcoSmart ECO 11 Tankless Water Heater
Available immediately
free shipping
  • 99% thermal energy efficient, saving energy compared to traditional tank heaters
  • provides between 1.3 and 3.1 gallons per minute based on inlet water temperature
  • temperature can be adjusted between 80-140°F in 1-degree increments
Our rating
9,5
very good
500+ purchases last month
ORBEK 14kW Electric Tankless Water Heater
ORBEK 14kW Electric Tankless Water Heater
Available immediately
free shipping
  • high energy efficiency with water-electricity separation minimizes scale and corrosion, potentially reducing electricity costs by up to 60%
  • flow rate of up to 3.38 gallons per minute, comfortably supplying hot water to 2-3 points of use simultaneously
  • stability in temperature control with built-in chip adjusting heating power to maintain water temperature within 1°F
Our rating
9,4
good
Titan Tankless Water Heater
Titan Tankless Water Heater
Available immediately
free shipping
  • enables energy savings
  • has a compact design
  • features adjustable temperature control
Our rating
9,1
good
200+ purchases last month
Tankless Electric 110V Water Heater 3000W, Under Sink with Digital Display
Tankless Electric 110V Water Heater 3000W, Under Sink with Digital Display
Available immediately
free shipping
  • thermal efficiency of 98% helps save energy
  • flow rate ranges from 0.3 to 0.5 gallons per minute based on water temperature
  • temperature can be adjusted between Fahrenheit and Celsius
Our rating
8,9
good
Electric Tankless Water Heater 240V-7000W with Digital Display
Electric Tankless Water Heater 240V-7000W with Digital Display
Available immediately
free shipping
  • reduces energy consumption by adjusting power input based on water flow and temperature
  • supplies instant hot water at temperatures of 131°F or higher in seconds
  • compact and lightweight design is easy to install and perfect for limited spaces
Our rating
8,6
good

Similar tankless water heater comparisons

tankless water heaters buying guide: How to choose the right product from the above tankless water heaters test or comparison

Understanding Tankless Water Heaters: How They Work

The Basics of Tankless Water Heating

Tankless water heaters, also known as on-demand water heaters, are designed to heat water only when it is needed. Unlike traditional water heaters that store a large volume of heated water in a tank, tankless models eliminate the standby energy loss that occurs when hot water sits in a tank waiting for use. When you turn on a hot water faucet, cold water travels through a pipe into the unit. A gas burner or an electric element heats the water as it flows through, providing a steady supply of hot water. This means that you can enjoy instant hot water without worrying about running out.

Components and Functionality

The key components of a tankless water heater include a heating element, a flow sensor, and a control system. The flow sensor detects when a tap is opened and activates the heater, while the control system regulates the heating process, ensuring that you receive water at the desired temperature. The entire process is efficient and allows for flexible installation options since you don’t have to accommodate a bulky tank. Whether you are replacing an old water heater or installing a new one, tankless options can fit seamlessly into your home’s plumbing.

Key Benefits of Switching to a Tankless Water Heater

Endless Hot Water Supply

One of the most appealing benefits of tankless water heaters is the endless hot water supply. If you have a large family or enjoy long showers, this feature is a game-changer. No longer will you have to schedule showers around the availability of hot water. With tankless systems, each family member can enjoy a comfortable shower without worrying about running out of hot water.

Energy Efficiency and Lower Bills

Tankless water heaters are known for their energy efficiency. Since they heat water on demand, they use significantly less energy compared to traditional models. This efficiency translates to lower utility bills. You might notice a dramatic reduction in your heating costs, especially if your household commonly uses hot water throughout the day.

Space-Saving Design

Another advantage is their compact design. Tankless water heaters can be mounted on walls or tucked into smaller spaces, freeing up valuable floor space. This is particularly beneficial in homes with limited space, where every square foot counts. You have the freedom to utilize your space for other important areas or amenities.

Choosing the Right Size Tankless Water Heater for Your Home

Assessing Your Hot Water Needs

When selecting a tankless water heater, it’s crucial to choose the right size that matches your household’s hot water needs. You’ll want to consider the peak hour demand—the maximum amount of hot water required during the busiest hour of your day. For instance, if multiple showers, dishwashing, and laundry occur simultaneously, a higher flow rate is necessary to maintain comfort.

Calculating Flow Rates

Flow rates are measured in gallons per minute (GPM). A typical shower uses about 2.5 GPM, while dishwashers and washing machines can range from 1.5 to 2.5 GPM. By assessing the total GPM needed during peak times and matching that with the heater’s specifications, you can ensure that your unit meets your home’s requirements. Manufacturers often provide charts or calculators to help you find the appropriate model.

Cost Considerations: Upfront Investment vs Long-Term Savings

Initial Purchase and Installation Costs

Upfront costs for tankless water heaters can be higher than traditional tank models; however, it’s essential to think about the long-term savings they offer. The price for a tankless system can vary based on the model, fuel type, and installation needs. Installation may require modifications to your plumbing or gas lines, which can add to the initial investment.

Evaluating Long-Term Savings

Despite the higher upfront costs, tankless water heaters can save you money over time. They typically have a longer lifespan—often lasting over 20 years compared to traditional models that may only serve for about 10-15 years. Additionally, their energy efficiency leads to lower utility bills, allowing these savings to quickly outpace the initial expense. Over the years, many homeowners find that their tankless system pays for itself through energy savings.

Installation Insights: What to Expect and How to Prepare

Preparation for Installation

Preparing for the installation of a tankless water heater involves several steps. First, if you’re replacing an old model, consider having a plumber assess your home’s plumbing. This will help determine whether any modifications need to be made for the new unit, particularly regarding venting and gas line installation. Ensure that the area where the heater will be installed is clear and accessible.

What to Expect During the Process

On installation day, expect the process to take a few hours or possibly longer, depending on whether any additional work is required. Your chosen installation professional will handle disconnecting your old unit and setting up the new one. It’s a good idea to discuss the proper usage of the new system once it’s installed, including how to adjust temperature settings and routine maintenance tips. After this, you’ll be ready to enjoy the benefits of your new tankless water heater.

Table of contents
  1. Understanding Tankless Water Heaters: How They Work
  2. Key Benefits of Switching to a Tankless Water Heater
  3. Choosing the Right Size Tankless Water Heater for Your Home
  4. Cost Considerations: Upfront Investment vs Long-Term Savings
  5. Installation Insights: What to Expect and How to Prepare

Overview

1. Comparison winner
Rheem RTG-70XLN-3 Outdoor Tankless Gas Water Heater
Our rating
9,8
very good
Rheem RTG-70XLN-3 Outdoor Tankless Gas Water HeaterAvailable immediately
2. Best value
FOGATTI InstaShower 8 Plus RV Tankless Water Heater
Our rating
9,8
very good
FOGATTI InstaShower 8 Plus RV Tankless Water HeaterAvailable immediately
Rinnai RX199iN Tankless Water Heater
Our rating
9,8
very good
Rinnai RX199iN Tankless Water HeaterAvailable immediately
GIRARD Tankless RV Water Heater 2022107534
Our rating
9,8
very good
GIRARD Tankless RV Water Heater 2022107534Available in a few days
5. Bestseller
EcoSmart ECO 27 Electric Tankless Water Heater 27kW
Our rating
9,8
very good
EcoSmart ECO 27 Electric Tankless Water Heater 27kWAvailable immediately
Rheem 18kW Tankless Electric Water Heater
Our rating
9,8
very good
Rheem 18kW Tankless Electric Water HeaterAvailable immediately
Ranein 2025 GEN II Tankless Water Heater
Our rating
9,6
very good
Ranein 2025 GEN II Tankless Water HeaterAvailable immediately
Stiebel Eltron Tempra 29 Plus Tankless Water Heater
Our rating
9,6
very good
Stiebel Eltron Tempra 29 Plus Tankless Water HeaterAvailable immediately
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