Best Natural Gas Tankless Water Heater: Tested and Reviewed

When it comes to upgrading your home’s water heating system, a natural gas tankless water heater is one of the smartest investments you can make. These innovative systems provide endless hot water on demand, reduce energy consumption, and free up valuable space in your home. But with so many options on the market, how do you choose the best one? In this guide, we’ve done the hard work for you by testing and reviewing the top natural gas tankless water heaters available. Whether you’re looking for energy efficiency, high performance, or affordability, there’s something here for every home.

List of the Best Natural Gas Tankless Water Heater:

Check out the thorough review of the best natural gas tankless water heater below.

1. Rinnai RX199iN Natural Gas Tankless Water Heater

The Rinnai RX199iN Condensing Smart Sense Tankless Water Heater sets a high standard for modern water heating systems. With a maximum flow rate of 11.1 GPM and an impressive 199,000 BTU, it delivers enough hot water to serve up to 7 fixtures simultaneously, making it ideal for large households. Thanks to its innovative Smart Sense gas control system, the unit adapts seamlessly to either natural gas or propane, providing flexibility for installation. Its compact design, comparable to a small suitcase, ensures it fits effortlessly into tight spaces, whether installed indoors or outdoors, supported by the Versa Vent feature.

The RX199iN achieves a UEF rating of 0.98, placing it among the most energy-efficient water heaters available. This translates to significant energy savings over time. The Quick Flush feature simplifies maintenance, and the option to integrate Wi-Fi control through the Control-R module offers additional convenience. Weighing just 55 pounds and consuming only 98 watts, this unit combines portability with high performance.

Key Features, Pros, and Cons

Key Features:

1. Compact size with indoor/outdoor versatility via Versa Vent.
2. Smart Sense system compatible with natural gas or propane.
3. UEF 0.98 for exceptional energy efficiency.
4. 11.1 GPM flow rate to support up to 7 fixtures.
5. Quick Flush feature for easy maintenance.

Pros:

• High energy efficiency with ENERGY STAR certification.
• Compact, space-saving design.
• Flexible fuel and installation options.
• Advanced technology for easy operation and maintenance.
• Supports multiple fixtures simultaneously.

Cons:

• Outdoor installation requires an RX-OVC vent cap.

2. Rheem Natural Gas Tankless Water Heater

The Rheem RTGH-95DVLN-3 is a top-tier indoor natural gas tankless water heater designed to meet the demands of modern households. With a maximum flow rate of 9.5 GPM and a powerful 199,900 BTU, it provides a consistent supply of hot water, ideal for medium to large homes. Its compact size (17.7″ W x 23.7″ H) and lightweight design (59.88 lbs) make it perfect for installation in tight spaces, saving valuable floor area. The stainless steel construction ensures durability and resistance to corrosion, making it a long-term investment for your home.

This unit stands out with Rheem’s Hot Start Programming, which eliminates cold water bursts during back-to-back use, enhancing comfort and efficiency. Its integrated digital display allows for easy temperature adjustments between 100°F and 140°F (default at 120°F). The electric ignition minimizes standby energy loss, further boosting efficiency. Moreover, the water heater is backed by strong warranties: 15 years on the heat exchanger, 5 years on parts, and 1 year for labor, ensuring peace of mind.

Key Features, Pros, and Cons

Key Features:

1. Compact stainless steel design with wall-mount capability.
2. Hot Start Programming prevents cold water bursts.
3. Adjustable temperature range: 100°F to 140°F.
4. High efficiency with 9.5 GPM flow rate.
5. Long-lasting warranties for parts and labor.

Pros:

• Delivers consistent hot water.
• Durable stainless steel construction.
• Compact size saves space.
• Easy temperature control with a digital display.
• Energy-efficient with electric ignition.

Cons:

• Limited outdoor installation options.

3. Ranein Natural Gas Tankless Water Heater

The Ranein Natural Gas Tankless Water Heater with Vent Pipe offers an efficient and compact solution for your household hot water needs. With a heating capacity of 100,000 BTU and a maximum flow rate of 4.3 GPM, it is ideal for supplying continuous hot water to 2-3 water outlets, such as a bathroom, kitchen, or bar area. Its compact dimensions (18.89″ W x 8.85″ H) make it a space-saving option for indoor installations, and its low wattage of 7.8 watts adds to its energy efficiency.

This tankless water heater stands out with its innovative Four Seasons Function, which automatically adjusts water temperature according to seasonal changes. The Kitchen Function provides a default water temperature of 100°F, ensuring precise and convenient operation for cooking and cleaning. Additionally, the built-in Bathtub Function allows users to set output water quantity with a reminder, enhancing versatility.

By eliminating preheating wait times, the Ranein tankless water heater delivers instant hot water while reducing energy consumption through its oxygen-free copper water tank. The included exhaust pipe simplifies installation, saving extra costs.

Key Features, Pros, and Cons

Key Features

1. Compact, space-saving design with included vent pipe.
2. Four Seasons Function adjusts temperature automatically.
3. 4.3 GPM flow rate suitable for 2-3 water outlets.
4. Instant hot water with no preheating required.
5. Energy-efficient oxygen-free copper water tank.

Pros

• Provides continuous, on-demand hot water.
• Compact and easy to install.
• Seasonal and customizable temperature features.
• Includes vent pipe, saving additional costs.
• Good value for money.

Cons

• Limited functionality in areas over 2,000 feet of elevation.

4. Rinnai RUCS65IN Natural Gas Tankless Hot Water Heater

The Rinnai RUCS65IN Tankless Hot Water Heater offers an energy-efficient and compact solution for modern households. With a 6.5 GPM flow rate, this natural gas-powered water heater ensures a steady and powerful supply of hot water, serving up to 5 appliances simultaneously. Its condensing technology conserves energy by only heating water when necessary, significantly reducing utility bills compared to traditional tank systems. Measuring 22″ W x 34″ H, it is a space-saving option perfect for indoor installations.

The RUCS65IN is designed with multiple venting options, including PVC/CPVC compatibility using the Ubbink Concentric to Twin Pipe adaptor, offering flexibility in placement. Its durable polyvinyl chloride construction enhances longevity, while the included warranties—12 years for the heat exchanger, 5 years for parts, and 1 year for labor—provide added peace of mind. This model is best suited for small to medium-sized homes, offering reliable hot water performance while maintaining energy and space efficiency.

Key Features, Pros, and Cons

Key Features

1. High-performance 6.5 GPM flow rate serves up to 5 appliances.
2. Compact design with condensing technology for energy efficiency.
3. Flexible venting options for adaptable installation.
4. Durable polyvinyl chloride construction.
5. Backed by extensive warranties for heat exchanger, parts, and labor.

Pros

• Endless hot water supply with energy savings.
• Compact, space-saving design.
• Multiple venting options enhance placement flexibility.
• Long warranties for reliable performance.
• Cost-effective upgrade from traditional tank heaters.

Cons

• Limited to indoor use only.

5. MIZUDO Natural Gas Tankless Water Heater

The MIZUDO Natural Gas Tankless Water Heater is a compact and efficient solution for small households or single-use applications. With a maximum flow rate of 3.6 GPM and a heating capacity of 80,000 BTU, it delivers consistent and reliable hot water on demand. Its compact design (13″ W x 20.5″ H) saves over 50% of the space compared to traditional tank water heaters, making it ideal for homes with limited installation space.

Equipped with CSA certification, this water heater ensures safety with features such as overheating protection and flameout protection. The oxygen-free copper water tank reduces heat loss, enhancing efficiency and durability. Additionally, the Uniform Energy Factor (UEF) of 0.81 ensures energy conservation by consuming power only during operation, keeping utility costs low. Its Exclusive Comfortech technology provides precise temperature control, eliminating fluctuations commonly known as “temperature sandwiches.”

Key Features, Pros, and Cons

Key Features

1. 3.6 GPM flow rate with 80,000 BTU heating capacity.
2. Compact design saves over 50% space compared to tank systems.
3. CSA-certified with safety features like overheating and flameout protection.
4. Oxygen-free copper water tank for efficiency and durability.
5. UEF rating of 0.81 ensures energy conservation.

Pros

• Endless hot water with precise temperature control.
• Compact and space-saving design.
• Easy installation with clear instructions.
• Energy-efficient and cost-effective.
• Certified for safety with reliable protection features.

Cons

• Limited to small households or single-point use.

6. Orbek Natural Gas Tankless Water Heater

The Orbek 80,000 BTU Residential Indoor Natural Gas Tankless Water Heater is a compact and efficient solution for small to medium households. Delivering up to 3.6 GPM, it can comfortably serve 1-3 fixtures simultaneously, making it ideal for kitchens, bathrooms, or other residential needs. Its advanced Four Seasons Function ensures energy-efficient operation by adjusting heating modes to match seasonal hot water requirements, reducing energy costs while providing a seamless experience.

Designed with safety in mind, the unit is CSA certified and features multiple protections, including dry combustion, overheat, flame failure, and water pressure protection. The oxygen-free copper heat exchanger ensures efficient heat transfer and corrosion resistance, enhancing durability and performance. With a compact size of 13″W x 20.5″H, it saves over 50% of the space compared to traditional tank water heaters, fitting effortlessly into tight indoor spaces.

Key Features, Pros, and Cons

Key Features

1. 3.6 GPM flow rate with 80,000 BTU heating capacity.
2. Compact design saves over 50% space compared to tank heaters.
3. Advanced safety features with CSA certification.
4. Stable temperature control within 1°F using built-in chip technology.
5. LED digital display with adjustable temperature and memory function.

Pros

• Provides reliable on-demand hot water for multiple fixtures.
• Energy-efficient with seasonal adjustment modes.
• Compact, space-saving design.
• Strong safety features and durable copper heat exchanger.
• Easy installation with standard venting and connectors.

Cons

• Limited to small to medium households.

How to Choose the Best Natural Gas Tankless Water Heater?

When it comes to selecting the perfect natural gas tankless water heater for your home, the process might seem overwhelming. With so many options available, how do you know which one is right for you?

Understand Your Hot Water Needs

Before diving into the specifications of water heaters, take a moment to assess your household’s hot water requirements. Ask yourself:

• How many people live in your home?
• Do you frequently use multiple water outlets at the same time (e.g., shower and kitchen sink)?
• What’s the climate like in your area?

These questions will help you determine the right size and flow rate (measured in gallons per minute or GPM) for your needs. For example, a family of four might need a water heater with a flow rate of 7–9 GPM, while a single-person household could get by with 3–5 GPM.

Consider Energy Efficiency

One of the biggest advantages of tankless water heaters is their energy efficiency. Look for models with a high Energy Factor (EF) or Uniform Energy Factor (UEF). The higher these ratings, the more energy-efficient the unit is, which means lower utility bills for you.

For even greater savings, opt for a model that is ENERGY STAR certified. This certification ensures the water heater meets strict energy efficiency guidelines set by the Environmental Protection Agency (EPA).

Choose the Right Size for Your Home

When choosing a natural gas tankless water heater, size truly matters. Unlike traditional tank heaters, tankless models are designed to provide hot water on demand. However, selecting the wrong size could leave you with lukewarm water during peak usage.

For a quick guide:

• Small homes or apartments: A compact unit with 3–5 GPM should suffice.
• Medium-sized homes: Look for a model with 6–9 GPM.
• Large homes: Opt for a high-capacity water heater with 9+ GPM to ensure simultaneous hot water supply.

If you’re unsure, always consult the manufacturer’s sizing chart or talk to a professional plumber.

Think About Venting Options

Venting is an essential consideration when installing a natural gas tankless water heater. There are two primary types of venting:

1. Direct vent: Pulls in air from outside and exhausts fumes through a pipe. This is ideal for homes with limited ventilation space.
2. Power vent: Uses indoor air for combustion and requires a fan to vent fumes outside.

Ensure your home is compatible with the venting system of the water heater you choose, as this can affect both installation costs and overall performance.

Evaluate the Climate in Your Area

Believe it or not, your location plays a big role in choosing the right tankless water heater. If you live in a colder climate, you’ll need a more powerful unit to heat incoming cold water to the desired temperature. Warmer regions, on the other hand, can rely on less powerful models since the water starts at a higher temperature.

Pro tip: Look for models with advanced temperature controls or cold-weather features to ensure consistent hot water, even during chilly winters.

Prioritize Durability and Warranty

A tankless water heater is an investment, so durability matters. Look for models with stainless steel heat exchangers as they are resistant to corrosion and provide a longer lifespan. Additionally, check the warranty—reliable brands often offer warranties of 10–15 years, giving you peace of mind.

Consider Additional Features

Modern tankless water heaters come with various features to enhance user experience. Here are some to look out for:

• Wi-Fi connectivity: Allows you to monitor and control your water heater remotely.
• Scale detection: Alerts you if mineral buildup is affecting the efficiency of the unit.
• Self-modulating technology: Adjusts the gas usage based on demand, ensuring energy savings.

While these features might come at a slightly higher price, they can greatly improve convenience and performance.

Check Your Budget

Lastly, your budget will play a key role in your decision. While natural gas tankless water heaters are more expensive upfront than traditional tank heaters, they save money in the long run by reducing energy costs and lasting longer. Compare models within your price range and weigh their features against your needs. Remember, the cheapest option may not always be the best in terms of efficiency and longevity.

Why Choose a Natural Gas Tankless Water Heater?

Now that you know what to look for, let’s revisit why natural gas tankless water heaters are worth it. These units provide unlimited hot water, are energy-efficient, and take up less space compared to traditional water heaters. Plus, they’re eco-friendly, reducing your carbon footprint while keeping your showers steamy.

Frequently Asked Questions When Selecting the Best Natural Gas Tankless Water Heater

1. What is a natural gas tankless water heater, and how does it work?

A natural gas tankless water heater is a system that heats water on demand without storing it in a tank. When you turn on a hot water tap, cold water flows through the heater’s heat exchanger, where it is warmed by a natural gas burner. This provides an endless supply of hot water, as long as the flow rate does not exceed the unit’s capacity.

2. Why should I choose a natural gas tankless water heater over a traditional tank water heater?

Tankless water heaters are more energy-efficient, as they only heat water when needed, rather than maintaining a full tank of heated water 24/7. They also save space due to their compact size and can last up to 20 years with proper maintenance, compared to 10–15 years for traditional water heaters. Additionally, they provide endless hot water, making them ideal for households with high hot water demands.

3. How do I determine the right size of a tankless water heater for my home?

To choose the right size, calculate the total flow rate (in gallons per minute or GPM) of all water outlets you might use simultaneously, such as showers, faucets, and dishwashers. Then, consider the temperature rise required (the difference between the incoming water temperature and the desired hot water temperature). For example, a family of four typically needs a unit with a flow rate of 7–9 GPM, while a smaller household may only need 3–5 GPM. Always consult the manufacturer’s sizing guide for precise recommendations.

4. Are natural gas tankless water heaters energy-efficient?

Yes, they are highly energy-efficient because they only heat water when it’s needed, reducing standby energy loss. Many models have an Energy Factor (EF) or Uniform Energy Factor (UEF) of 0.8 or higher, meaning they convert at least 80% of the gas they use into heat. ENERGY STAR-certified models are even more efficient, which can save you up to 30% on energy costs compared to traditional tank water heaters.

5. What are the venting requirements for a natural gas tankless water heater?

Venting is essential for the safe operation of natural gas tankless water heaters, as it removes combustion gases from the home. There are two main types of venting:

• Direct venting: Pulls air from outside and vents exhaust gases back outdoors through a sealed system.
• Power venting: Uses indoor air for combustion and vents gases outside using a fan.
  Ensure your home has the appropriate venting setup for the model you choose, as improper venting can affect performance and safety.

6. Can I install a natural gas tankless water heater myself?

While it’s possible for experienced DIY enthusiasts to install a tankless water heater, professional installation is highly recommended. This ensures proper gas connections, venting, and compliance with local building codes. Incorrect installation can lead to safety hazards, reduced efficiency, or damage to the unit.

7. How much does a natural gas tankless water heater cost?

The cost of a natural gas tankless water heater ranges from $500 to $2,500, depending on the brand, size, and features. Installation costs typically add another $500 to $1,500, depending on the complexity of the job. While the upfront cost is higher than a traditional tank water heater, the energy savings and longer lifespan can make it a cost-effective investment in the long run.

8. What maintenance does a natural gas tankless water heater require?

To keep your water heater running efficiently, perform regular maintenance, including:

• Flushing the system annually to remove mineral buildup, especially if you live in an area with hard water.
• Cleaning the air filter and checking the venting system for blockages.
• Inspecting the gas lines and connections for leaks.
  Many manufacturers include maintenance instructions in their user manuals, or you can hire a professional for routine servicing.

9. Are natural gas tankless water heaters suitable for cold climates?

Yes, but it’s important to choose a model with enough heating power to handle the lower incoming water temperatures in colder climates. Some models are specifically designed for cold regions and feature freeze protection to prevent damage during winter. Look for units with advanced temperature controls and a higher BTU rating to ensure consistent hot water in cold conditions.

10. How long do natural gas tankless water heaters last?

With proper maintenance, a natural gas tankless water heater can last up to 20 years or more. This is significantly longer than the lifespan of a traditional tank water heater, which typically lasts 10–15 years. Regularly flushing the unit and inspecting its components can help maximize its lifespan.

11. What features should I look for in the best natural gas tankless water heater?

When choosing a water heater, consider the following features:

• High flow rate: Matches your household’s water demand.
• Energy efficiency: Look for a high UEF rating and ENERGY STAR certification.
• Durability: Models with stainless steel heat exchangers last longer.
• Advanced controls: Features like Wi-Fi connectivity, self-modulating gas burners, and digital temperature controls add convenience.
• Warranty: A longer warranty indicates a higher-quality unit.

12. Do natural gas tankless water heaters work during a power outage?

Most natural gas tankless water heaters require electricity to power components such as ignition, fans, and control panels. During a power outage, they will not function unless you have a backup power source, such as a generator or battery system. Some models offer non-electric options, but these are less common.

13. What are the best brands for natural gas tankless water heaters?

Popular and reliable brands include Rinnai, Rheem, Noritz, Takagi, Navien, and Bosch. Each brand offers a range of models with various capacities, features, and price points to suit different needs. Research customer reviews and product specifications to find the best fit for your home.

14. Are natural gas tankless water heaters environmentally friendly?

Yes, natural gas tankless water heaters are more environmentally friendly than traditional tank heaters. Their energy-efficient operation reduces greenhouse gas emissions, and many models use advanced technology to minimize waste and optimize performance.

15. How can I ensure my natural gas tankless water heater is safe?

To ensure safety, always follow the manufacturer’s installation and maintenance guidelines. Install carbon monoxide detectors near the unit to monitor gas emissions. Regularly inspect the venting system, gas lines, and connections for leaks or damage. Hiring a licensed professional for installation and servicing can also help prevent safety risks.

16. Can I use a natural gas tankless water heater in a mobile home or RV?

Yes, some natural gas tankless water heaters are specifically designed for mobile homes or RVs. These models are compact, lightweight, and equipped with special venting systems to accommodate smaller spaces. Be sure to choose a unit approved for mobile installations.

Conclusion

Choosing the best natural gas tankless water heater doesn’t have to be a challenge. After testing and reviewing the top models on the market, it’s clear that the right choice depends on your household’s hot water needs, energy efficiency goals, and budget. A tankless water heater not only delivers endless hot water but also saves money in the long run by reducing energy bills.

Enjoyed this guide of the best natural gas tankless water heater? Then be sured to check out our other heating guides.

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