Best Exterior Tankless Hot Water Heaters

Imagine a chilly morning where you’re waiting for hot water to fill your shower, only to be met with lukewarm disappointment. This common scenario leads many homeowners to search for efficient water heating solutions. Exterior tankless hot water heaters offer a practical remedy by delivering hot water on demand, eliminating the hassle of waiting for a tank to refill.

When evaluating tankless water heaters, key features include flow rate, energy efficiency, heating capacity, and installation requirements. High-performance models can provide continuous hot water while reducing energy consumption, making them ideal for larger households and environmentally conscious consumers.

In this guide, we’ve rounded up the five best exterior tankless hot water heaters available today. From reliable brands to cutting-edge technology, these picks cater to various household needs and budgets, ensuring you find the right fit for your home.

Comparing key specifications can help you make an informed decision:

Features	Rheem 7.0 GPM LP	Rheem 7.0 GPM NG	Westinghouse 8.1 GPM	CAMPLUX 8.4 GPM	Rinnai RE140eN
Flow Rate	7.0 GPM	7.0 GPM	8.1 GPM	8.4 GPM	5.3 GPM
Heating Capacity	160,000 BTU	160,000 BTU	180,000 BTU	199,000 BTU	140,000 BTU
Energy Factor	0.82 UEF	0.82 UEF	95% Efficiency	84% Efficiency	Non-Condensing
Best for	Large Families	Large Families	Multi-Point Use	Medium Homes	Compact Spaces
Warranty	15 Years	15 Years	2 Years	1 Year	15 Years

Rheem RTG Series 7.0 GPM LP

This Rheem model is a liquid propane tankless water heater designed for whole-house residential use. With a flow rate of 7.0 GPM, it’s ideal for larger households needing consistent hot water for multiple showers or appliances at once.

What sets this unit apart is its high efficiency, providing 160,000 BTUs of heating capability while saving up to 34% on energy costs compared to traditional electric tank heaters. The outdoor installation means you won’t need complicated venting, and it features advanced safety measures for peace of mind.

However, this model requires professional installation, which may add to overall costs. If you prefer a more DIY-friendly option, this might not be the best choice for you.

• Flow Rate: 7.0 GPM
• Heating Capacity: 160,000 BTU
• Energy Factor: 0.82 UEF
• Durable metal cabinet
• 15-year heat exchanger warranty

Best for: Large families needing consistent hot water.

Rheem RTG Series 7.0 GPM NG

This model mirrors the liquid propane version but runs on natural gas, offering the same flow rate of 7.0 GPM. It’s an excellent choice for households that have natural gas lines already installed.

It provides the same benefits in terms of energy efficiency and heating capacity. The non-condensing design further simplifies installation, making it a practical option for outdoor setups.

While the initial cost may be slightly higher than conventional heaters, you’ll enjoy lower operating costs due to its efficiency. The requirement for professional installation remains a consideration.

• Flow Rate: 7.0 GPM
• Heating Capacity: 160,000 BTU
• Energy Factor: 0.82 UEF
• Built-in freeze protection
• 15-year heat exchanger warranty

Best for: Homeowners with natural gas access.

Westinghouse Gas Tankless

The Westinghouse tankless water heater stands out with a substantial 8.1 GPM flow rate, making it suitable for larger homes or those with multiple bathrooms. It delivers up to 180,000 BTUs of heating power.

Its self-modulating technology ensures precise temperature control within ±1°F, reducing the risk of cold bursts during use. This feature is particularly beneficial for families who need reliable hot water simultaneously for showers, laundry, and dishwashing.

A potential downside is the warranty, which is shorter than some competitors at two years for the unit. Additionally, installation might require specific plumbing configurations, which could increase setup costs.

• Flow Rate: 8.1 GPM
• Heating Capacity: 180,000 BTU
• Temperature Stability: ±1°F
• CSA-certified for safety
• 2-year unit warranty

Best for: Homes with multiple fixtures in use.

CAMPLUX 199,000 BTU Tankless

This powerful outdoor propane tankless water heater boasts an impressive 8.4 GPM flow rate, making it suitable for mid-sized homes and apartments. It’s designed to serve 3-8 persons, ensuring ample hot water for daily needs.

The model’s advanced features include an intelligent thermostat for precise temperature control and a weather-resistant design, making it ideal for outdoor installation. It also comes with multiple safety features, including anti-freezing and overheat protections.

However, while the higher BTU rating indicates great performance, it may come with increased fuel costs during peak usage. Also, its installation might require professional assistance, depending on your existing setup.

• Flow Rate: 8.4 GPM
• Heating Capacity: 199,000 BTU
• Temperature Control: ±0.5°F
• Weather-resistant design
• 1-year limited warranty

Best for: Mid-size homes needing high performance.

Rinnai RE140eN Non-Condensing

The Rinnai RE140eN is a compact, non-condensing natural gas tankless water heater that provides a flow rate of up to 5.3 GPM. Its compact size makes it ideal for those with limited installation space.

One of its notable features is the smart design that minimizes energy use by heating water only when necessary. It also includes an LED screen for service reminders, making maintenance straightforward.

However, the lower flow rate may not suffice for larger households needing multiple outlets running simultaneously. Buyers should consider their specific hot water demands carefully before choosing this model.

• Flow Rate: 5.3 GPM
• Heating Capacity: 140,000 BTU
• Compact size
• LED service reminder screen
• 15-year heat exchanger warranty

Best for: Limited spaces or smaller households.

How We Chose These Products

We evaluated these exterior tankless water heaters based on several key factors: flow rate, energy efficiency, heating capacity, safety features, and warranty offerings. Each product was chosen for its performance reliability, user reviews, and brand reputation in the market.

Installation complexity and maintenance requirements also played a role in our selection. We aimed to include models that cater to a variety of household sizes and needs, ensuring there’s a suitable option for every potential buyer.

Buying Guide: What Really Matters

When choosing an exterior tankless hot water heater, consider your household’s hot water demand. Calculate the peak flow rate needed during busy times, such as showering and running appliances simultaneously. This will help you select a model with an adequate GPM rating.

Energy efficiency is another critical factor. Look for models with higher Uniform Energy Factor (UEF) ratings, as these indicate better energy savings over time. Additionally, consider installation requirements, including whether you’ll need professional help or if you can handle it yourself.

Our Top Recommendation

For most users, the Rheem RTG Series 7.0 GPM models (both propane and natural gas) offer the best balance of performance, efficiency, and warranty coverage, making them the top choice for large families. For those with slightly lower hot water needs, the Westinghouse model is an excellent runner-up.

Frequently Asked Questions

What is the lifespan of a tankless water heater? Most tankless water heaters can last 15-20 years with proper maintenance, significantly longer than traditional tank heaters.

Can I install a tankless water heater myself? While some experienced DIYers can manage installation, professional installation is recommended to ensure safety and proper functionality.

What maintenance do tankless water heaters require? Regular maintenance includes descaling to prevent mineral buildup, checking filters, and ensuring vents are clear for safe operation.

How does a tankless water heater save energy? Tankless water heaters heat water on demand, reducing standby energy loss associated with traditional tank heaters.

Can tankless water heaters work in cold climates? Yes, many models are designed with freeze protection features, making them suitable for installation in colder regions.