Best Exterior Tankless Gas Water Heaters

Imagine running multiple showers or appliances in your home without worrying about running out of hot water. This common dilemma is easily resolved with the right tankless water heater. These modern systems provide hot water on demand, making them a smart investment for busy households.

When searching for the best exterior tankless gas water heaters, you’ll want to consider factors like energy efficiency, flow rate, and safety features. The best units heat water quickly while minimizing energy costs, meaning you can enjoy comfort without breaking the bank.

In this review, we’ll explore five top-rated exterior tankless gas water heaters, each catering to different needs and preferences. Whether you have a large family or a smaller home, there’s an ideal option for you.

Here’s a quick comparison of the key specifications for our top picks:

Features	Rheem 8.4 GPM	Rheem 7.0 GPM	Westinghouse 8.1 GPM	Rheem 7.0 GPM LP	Rheem 7.0 GPM Indoor
Maximum Flow Rate	8.4 GPM	7.0 GPM	8.1 GPM	7.0 GPM	7.0 GPM
BTU Output	180,000 BTU	160,000 BTU	180,000 BTU	160,000 BTU	160,000 BTU
Energy Factor	0.82 UEF	0.82 UEF	Not Listed	0.82 UEF	0.82 UEF
Installation Type	Outdoor	Outdoor	Outdoor	Outdoor	Indoor
Warranty	15 years	15 years	2 years	15 years	5 years

Rheem RTG Series 8.4 GPM…

The Rheem RTG Series 8.4 GPM Natural Gas Tankless Water Heater is ideal for medium to large households needing constant hot water. With a maximum flow rate of 8.4 gallons per minute, it’s perfect for homes with multiple bathrooms or high hot water demand.

This unit stands out for its high BTU output of 180,000, allowing it to handle 3-4 simultaneous showers comfortably. Additionally, its energy efficiency reduces energy costs significantly compared to traditional tank systems.

However, professional installation is required, which can add to initial costs. While some may find the outdoor installation convenient, it may not suit every home layout.

• Flow Rate: 8.4 GPM
• BTU Output: 180,000
• Energy Factor: 0.82 UEF
• Outdoor installation
• 15-year heat exchanger warranty

Best for: Large families needing consistent hot water for multiple fixtures.

Rheem RTG Series 7.0 GPM…

The Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater is an excellent choice for average-sized families. It offers a flow rate of 7.0 GPM, which is sufficient for homes with 2-3 simultaneous hot water needs.

This model features the same excellent energy efficiency as its larger counterpart, providing savings on gas bills while ensuring you never run out of hot water. Its compact design allows for easy outdoor installation.

A potential downside is that its lower flow rate may not meet the needs of larger households during peak usage times.

• Flow Rate: 7.0 GPM
• BTU Output: 160,000
• Energy Factor: 0.82 UEF
• Outdoor installation
• 15-year heat exchanger warranty

Best for: Medium-sized families with moderate hot water demands.

Westinghouse Gas Tankless…

The Westinghouse Gas Tankless Water Heater delivers up to 8.1 GPM, making it suitable for larger homes or those with high hot water usage. It supports 3-5 fixtures running concurrently without a hitch.

What sets this model apart is its advanced self-modulating technology. This feature maintains a consistent water temperature, reducing the risk of cold bursts during showers, a common issue with lesser units.

One drawback is its shorter warranty period of 2 years, which may concern some buyers looking for long-term reliability. Installation requirements also include standard plumbing and power connections.

• Flow Rate: 8.1 GPM
• BTU Output: 180,000
• Precise temperature stability
• Outdoor installation
• 2-year limited warranty

Best for: Homes with multiple bathrooms needing stable hot water.

Rheem RTG Series 7.0 GPM…

This variant of the Rheem RTG Series offers a Liquid Propane option, ensuring versatility for homes that may not have natural gas access. It still provides a robust flow rate of 7.0 GPM, suitable for 2-3 fixtures.

It shares many features with the other Rheem models, including energy efficiency and a durable build. The propane option can be more readily available in some areas, making it a practical choice.

However, the unit’s compatibility with propane may require additional adjustments during installation, and the energy factor remains consistent but may not perform as well as natural gas under all conditions.

• Flow Rate: 7.0 GPM
• BTU Output: 160,000
• Energy Factor: 0.82 UEF
• Outdoor installation
• 15-year heat exchanger warranty

Best for: Homes with propane availability looking for efficient hot water solutions.

Rheem RTG Series 7.0 GPM…

This indoor variant of the Rheem RTG Series is designed for those needing a compact solution while still delivering solid performance. It also offers a flow rate of 7.0 GPM, making it effective for most households.

Noteworthy features include leak detection technology and a built-in freeze protection system, adding layers of security and reliability. Its indoor design frees up outdoor space, making it ideal for smaller properties.

The major limitation is its installation requirements, which may complicate setup, particularly for those not familiar with indoor venting systems. It also has a shorter warranty on parts compared to outdoor models.

• Flow Rate: 7.0 GPM
• BTU Output: 160,000
• Energy Factor: 0.82 UEF
• Indoor installation
• LeakGuard leak detection

Best for: Smaller homes needing an efficient indoor water heating solution.

How We Chose These Products

Our selection process involved evaluating each product based on key performance indicators such as flow rate, energy efficiency, and installation requirements. We prioritized models that deliver consistent hot water while minimizing energy costs, ensuring they meet a range of household needs.

Additionally, we considered the reliability and warranty offered by manufacturers, as these factors significantly impact long-term satisfaction. Customer reviews and expert recommendations helped validate our choices, ensuring a well-rounded selection.

Buying Guide: What Really Matters

When choosing an exterior tankless gas water heater, consider the flow rate as it directly affects how many fixtures can be used simultaneously without interruption. Evaluate your household’s hot water needs, especially during peak usage times.

Energy efficiency is another critical factor; models with higher energy factors will not only reduce your utility bills but also have a lower environmental impact. Lastly, ensure you understand the installation requirements and warranty coverage to avoid any surprises down the line.

Our Top Recommendation

For large families, the Rheem RTG Series 8.4 GPM model stands out as the best choice due to its impressive flow rate and energy efficiency. For those with smaller needs or budget constraints, the Rheem RTG Series 7.0 GPM offers an excellent balance of performance and cost. If you need a propane option, consider the Rheem RTG Series 7.0 GPM LP model for versatility, while the Westinghouse model excels in larger homes needing consistent performance.

Frequently Asked Questions

How do I determine the right flow rate? Assess your household’s simultaneous hot water needs to find a model that can accommodate them without running out.

Can I install a tankless water heater myself? While some may attempt DIY installation, professional installation is strongly recommended for gas units to ensure safety and compliance with local codes.

What maintenance is required for tankless water heaters? Regular descaling and flushing are necessary to maintain performance and extend the unit’s lifespan.

What is the lifespan of a tankless water heater? Most models have a lifespan of 15-20 years, significantly longer than traditional tank heaters.