Best 40 Gallon Propane Water Heaters: Top 10 Picks

The best 40 gallon propane water heater provides reliable, on-demand hot water for homes without natural gas or for off-grid living. Choosing the right model ensures consistent comfort and efficient operation for your household’s needs. Factors like BTU input, energy efficiency ratings, tank design, and venting options significantly impact performance and long-term cost-effectiveness.

A mismatch can lead to insufficient hot water during peak demand or premature component failure, wasting both energy and money. To help you make an informed decision, we’ve compiled a list of the top 10 best 40 gallon propane water heaters available, focusing on durability, heating speed, and user satisfaction.

For those seeking the best 40 gallon propane water heater alternatives, high-efficiency tankless models offer continuous hot water and space savings. The Rheem RTG-70XLP-3 and Rheem RTG-70DVLP-3 are strong contenders, providing up to 7.0 GPM and 160,000 BTUs, suitable for multiple simultaneous hot water demands in 2-3 bathroom homes.

Best 40 Gallon Propane Water Heater: At a Glance

Image	Product	Buy
Best Pick 1	NEW Rinnai RX180iN Condensing Smart Sense Natural Gas or Propane Best for: Smart home owners	Check Price
Best Pick 2	Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water Best for: Outdoor installations	Check Price
Best Pick 3	Rheem RTG-70DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water Best for: Indoor installations	Check Price
Best Pick 4	Westinghouse Smart Outdoor Propane Tankless Water Heater, 8.1 GPM 180,000 Best for: High-demand homes	Check Price
Best Pick 5	APUS Tankless Water Heater Propane, 140,000 BTU Indoor Installation Up Best for: Compact apartments	Check Price

How We Picked

We meticulously evaluated propane tankless water heaters for our best 40 gallon propane water heater guide, prioritizing build quality, real-world performance, and durability. Safety features and standout functionalities like indoor/outdoor versatility or advanced smart controls were heavily weighted. Models with significantly lower BTU outputs or flow rates that couldn’t realistically support multiple fixtures were ruled out.

We focused on units offering robust heating capacity and advanced design, ensuring long-term value and consistent hot water delivery for demanding households by 2026.

What Most Buyers Get Wrong

GPM: How Much Hot Water Do You Need?

When choosing a propane water heater, understanding Gallons Per Minute (GPM) is crucial. For a 40-gallon tankless model, higher GPM means more simultaneous hot water use. Rheem RTG-70XLP-3 and Rheem RTG-70DVLP-3 offer 7.0 GPM, ideal for multiple bathrooms.

Westinghouse models boast 8.1 GPM. If you have heavy demand, like multiple showers running, a higher GPM unit like the MIZUDO (10.3 GPM) might be overkill for a typical 40-gallon replacement scenario but good to know the range exists.

Tankless vs. Storage Tank: A Performance Difference

This roundup focuses on tankless propane water heaters, which heat water on demand, unlike traditional storage tank models. This means endless hot water without running out. Products like the Rinnai RX180iN and APUS models (140,000 BTU) provide continuous hot water. However, their initial output and recovery rate differ from what you might expect from older 40-gallon storage tank systems, especially in colder climates where water needs more heating energy.

1. NEW Rinnai RX180iN Condensing Smart Sense Natural Gas or Propane

Best for: Indoor/Outdoor Versatility & Dual Fuel.

This Rinnai RX180iN unit offers a dual-fuel system, operating on natural gas or propane, and can be installed indoors or outdoors, allowing installation flexibility for various home setups.

Boasting a high 0.98 UEF efficiency rating and a maximum flow rate of 10 GPM, this unit can simultaneously power up to six fixtures. Its compact, suitcase-sized design simplifies installation in tight spaces.

Pros

• Dual-fuel operation (natural gas or propane)
• Indoor and outdoor installation flexibility
• High flow rate of 10 GPM for multiple fixtures
• Smart home compatibility for remote control

Cons

• Requires a separate RX-OVC vent cap for outdoor installations.

This Rinnai unit is ideal for homeowners needing a flexible and powerful hot water solution that can adapt to different installation constraints and fuel types.

2. Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water

Best for: Outdoor Use & Strong Flow.

The Rheem RTG-70XLP-3 provides up to 7.0 GPM with 180,000 BTUs, ensuring enough hot water for 2–3 bathrooms simultaneously, even during peak demand.

Featuring hot-start programming to minimize cold water bursts and a durable metal cabinet designed for outdoor installation, this unit offers quick, reliable hot water delivery for busy households. It’s compatible with a 1/2 inch gas line.

Pros

• High flow rate of 7.0 GPM
• 180,000 BTU heat output for rapid heating
• Outdoor installation ready with durable cabinet
• Hot-start programming for reduced cold water

Cons

• Designed exclusively for outdoor installation, requiring a protected location.

This Rheem tankless water heater is perfect for homeowners with 2-3 bathrooms looking for a robust outdoor unit that can handle simultaneous hot water demands.

3. Rheem RTG-70DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water

Best for: Indoor Use & Efficient Heating.

Designed for indoor installations, this Rheem RTG-70DVLP-3 delivers 7.0 GPM of hot water with 160,000 BTUs, efficiently serving 2-3 bathrooms.

This unit utilizes hot-start programming to reduce cold water delays and features a compact metal cabinet for easy indoor wall mounting. It achieves an efficiency rating of 0.82 UEF, conserving energy.

Pros

• Suitable for indoor installation
• 7.0 GPM flow rate for multiple fixtures
• 160,000 BTU heat output
• Hot-start programming minimizes cold water

Cons

• Efficiency rating of 0.82 UEF is lower than some condensing models.

Ideal for homes requiring an indoor propane water heater that can reliably supply hot water to 2-3 bathrooms, the Rheem RTG-70DVLP-3 offers consistent performance.

4. Westinghouse Smart Outdoor Propane Tankless Water Heater, 8.1 GPM 180,000

Best for: Outdoor Use & Precise Temperature Control.

This Westinghouse Smart Outdoor Propane Tankless Water Heater outputs 8.1 GPM and 180,000 BTU, offering on-demand hot water for up to 5 fixtures.

Featuring precise ±1°F temperature stability through self-modulating technology, this unit ensures consistent water temperature. It’s designed for outdoor installation and includes remote control functionality for added convenience.

Pros

• High flow rate of 8.1 GPM
• Precise ±1°F temperature control
• Outdoor installation enabled
• Remote control included

Cons

• Relies solely on 120 Volts AC power, not battery backup.

This Westinghouse model is an excellent choice for larger homes or households demanding consistent temperatures for outdoor showers or pools, ensuring comfort and convenience.

5. APUS Tankless Water Heater Propane, 140,000 BTU Indoor Installation Up

Best for: Instant Hot Water & Smart Features.

The APUS Tankless Water Heater utilizes a 140,000 BTU burner and oxygen-free copper heat exchanger to provide hot water in as little as 1 second.

This unit features APUS’ exclusive Zero-Cold-Water Technology, eliminating cold water wait times and ensuring immediate comfort. It’s also WiFi enabled, allowing remote control via the Tuya APP for personalized settings.

Pros

• Instant hot water delivery (1 second)
• Zero-Cold-Water Technology
• WiFi remote control via Tuya APP
• 140,000 BTU burner for robust heating

Cons

• Flow rate of 6.8 GPM may be insufficient for very large households with many simultaneous users.

Perfect for tech-savvy homeowners seeking instant hot water and smart home integration, this APUS unit offers a modern and efficient solution for indoor use.

6. Rheem RTG-70XLN-3 High Efficiency Non-Condensing Outdoor Tankless Natural Gas Water

Best for: Outdoor Use & Self-Diagnostic Program.

Fueled by natural gas, the Rheem RTG-70XLN-3 delivers 7.0 GPM, suitable for 2–3 bathrooms with consistent hot water needs.

This outdoor tankless unit features a self-diagnostic program for easier troubleshooting and freeze protection for cold climates. Its 160,000 BTU output ensures rapid heating, and it supports an EZ-link cable for parallel installations.

Pros

• Designed for outdoor installation
• 7.0 GPM flow rate
• Self-diagnostic program for troubleshooting
• Freeze protection included

Cons

• This model is exclusively for natural gas, not propane.

This Rheem model is an excellent option for homes that use natural gas and require a durable, outdoor-installed water heater capable of supplying multiple bathrooms.

7. Ranein Propane Gas Tankless Water Heater, Indoor Max 4.3 GPM,

Best for: Multi-Function Modes & Compact Design.

This Ranein Propane Gas Tankless Water Heater offers four intelligent preset modes (4-season, Kitchen, Bathtub, Shower) for optimized performance and temperature control.

With a 100,000 BTU output and a flow rate of 4.3 GPM, it supports 3-4 water points simultaneously. The unit features continuous temperature sensing and gas-water linkage for precise heating up to 155°F.

Pros

• Four intelligent preset modes
• 4.3 GPM flow rate for multiple fixtures
• Max temperature of 155°F
• Compact design for indoor installation

Cons

• Lower flow rate of 4.3 GPM may not be sufficient for simultaneous use of more than 2-3 fixtures.

This Ranein unit is ideal for smaller homes or apartments where specific temperature settings for different uses, like bathing or washing dishes, are desired from an indoor propane heater.

8. MIZUDO Tankless Water Heater Propane, 199,000 BTU, Indoor Installation, Max

Best for: High Capacity & Smart WiFi Control.

The MIZUDO Tankless Water Heater boasts a powerful 199,000 BTU rating and a 10.3 GPM flow capacity, designed to support large households with 5-7 fixtures simultaneously.

This indoor unit offers smart WiFi connectivity for remote management via a mobile app, allowing users to adjust temperature and schedules. Its advanced sealed combustion system and anti-freeze protection enhance safety and durability.

Pros

• Extremely high flow rate of 10.3 GPM
• Smart WiFi and app control
• 199,000 BTU heating capacity
• Supports 5-7 usage points

Cons

• High BTU output may require specific gas line sizing and ventilation considerations.

This MIZUDO tankless water heater is best for large families or homes with high hot water demands that can utilize its substantial flow rate and smart home capabilities for an indoor setup.

9. Outdoor Tankless Water Heater, 130,000 BTU/5.3 GPM Propane Instant Hot

Best for: Outdoor Use & All-Weather Performance.

Designed for outdoor installation, this propane tankless heater delivers 5.3 GPM and 130,000 BTU, meeting daily household needs for 3–5 taps.

This unit features wind-resistant construction and electronic freeze protection, ensuring reliable operation in extreme weather conditions. It includes a convenient remote control for easy indoor operation and temperature adjustment up to 149°F.

Pros

• Suitable for outdoor installation
• 5.3 GPM flow rate
• 130,000 BTU output
• Electronic freeze protection

Cons

• Requires 110 Volts for ignition and control, not a standalone propane unit.

This outdoor propane water heater is a practical choice for garages, workshops, or guest houses requiring a dedicated hot water supply that can withstand various weather conditions.

10. APUS Tankless Water Heater Propane Gas, Up to 4.42 GPM,

Best for: Low-Flow Start & Auto Protection.

This APUS Tankless Water Heater features a 95,000 BTU heating capacity and a 4.42 GPM flow rate, with innovative 0.66 GPM low-flow start technology.

It effectively meets simultaneous hot water demands for 2 showers plus 1 sink, maintaining stable temperatures. Built-in features include anti-freezing protection, dry combustion protection, and overheat protection for safety and longevity.

Pros

• Low-flow start technology (0.66 GPM)
• 4.42 GPM flow rate for multiple fixtures
• 95,000 BTU heating capacity
• Multiple built-in safety protections

Cons

• Maximum flow rate might be insufficient for homes with more than 2-3 simultaneous users.

This APUS model is well-suited for smaller homes or apartments where efficient energy use and reliable hot water for 2-3 outlets are prioritized in an indoor propane setup.

BTU vs. GPM: The Real Propane Water Heater Bottleneck

The defining characteristic for a best 40 gallon propane water heater isn’t the total BTU output, but its Gallons Per Minute (GPM) rating, especially when multiple fixtures are demanding hot water simultaneously.

While units like the MIZUDO Tankless Water Heater Propane boast a massive 199,000 BTU and an advertised 10.3 GPM, capable of supporting 5-7 fixtures, this level of demand is overkill for most homes. More practical units, such as the Rheem RTG-70XLP-3 High Efficiency Non-Condensing Outdoor Tankless Liquid Propane Water, deliver 7.0 GPM with their 160,000 BTU. This is the sweet spot for many households, comfortably handling concurrent showers and appliance use without the energy waste associated with vastly oversized Heating elements.

Consider the APUS Tankless Water Heater Propane, which offers a respectable 4.42 GPM at 95,000 BTU. This unit is perfectly suited for smaller homes or those with infrequent simultaneous hot water needs. Its lower BTU also means a simpler propane connection and potentially less strain on your supply system, a crucial consideration many overlook when blinded by high flow rate numbers.

Similarly, the Ranein Propane Gas Tankless Water Heater, with its 4.3 GPM and 100,000 BTU, is a sensible choice for downsized demands.

The NEWRinnai RX180iN Condensing Smart Sense Natural Gas or Propane highlights another important distinction: installation flexibility. While its BTU and GPM are substantial, its ability to be installed indoors or outdoors offers a significant advantage for homes with limited exterior space. However, even this versatile unit’s ultimate utility hinges on matching its GPM to actual usage patterns, not just its stated heating power.

For homes where simultaneous use is common, prioritizing a higher GPM rating, like that found in the Westinghouse Smart Outdoor Propane Tankless Water Heater at 8.1 GPM, is far more impactful than simply selecting the highest BTU number. The Rheem RTG-70DVLP-3 High Efficiency Non-Condensing Indoor Tankless Liquid Propane Water, providing 7.0 GPM, is an excellent option for those needing indoor installation with robust performance.

What to Look for in a 40 Gallon Propane Water Heater

Vent type and requirements

For a 40-gallon propane water heater, prioritize direct-vent systems for their sealed combustion. This design pulls outside air for burning and vents exhaust directly through the wall, making it the safest and most efficient choice for enclosed spaces, eliminating the need for a chimney. While power-vent units use a fan to push exhaust out and conventional units rely on natural draft, direct-vent guarantees fresh air intake and prevents backdrafts.

Therefore, select a direct-vent model to ensure optimal performance and safety within your home. This is the definitive choice for most residential installations.

Energy efficiency and recovery rate

When evaluating energy efficiency and recovery, focus on the First Hour Rating (FHR). This metric indicates the total volume of hot water a heater can deliver in the first hour of use, crucial for households with simultaneous hot water demands. A higher FHR is always better, typically above 60 gallons for a 40-gallon tank.

While recovery rate (gallons per hour) and Energy Factor (EF) are important, FHR provides the most practical measure of immediate hot water availability. For robust performance, look for a gas input rate of 40,000 BTU/hr or higher.

Aim for the highest FHR your budget allows.

Physical dimensions and installation space

Consider the physical dimensions and installation space carefully. A standard 40-gallon propane water heater is typically around 50-60 inches tall with a 20-inch diameter. Crucially, check the required clearances for ventilation and servicing; these are non-negotiable for safe operation and maintenance.

Ensure the top or side water connections can be easily accessed in your chosen location. For most homes, a floorstanding unit is standard and easiest to install.

Measure your intended space precisely before purchase to avoid installation headaches.

Ignition system and thermostat control

The ignition system and thermostat control are key to ease of use and reliability. Electronic ignition systems are superior, offering instant ignition without a constantly burning pilot light, saving fuel and increasing safety. Look for a thermostat with a wide and precise temperature adjustment range, allowing you to set your ideal hot water temperature accurately.

Diagnostic lights indicating operational status and error codes are invaluable for troubleshooting. Always ensure the unit includes a built-in pressure relief valve for safety.

Choose an electronic ignition model with clear temperature controls for the best user experience.

Which Should You Choose?

• If you need to heat water for a large family with multiple simultaneous water demands (like showers and laundry), choose a unit with a high GPM (Gallons Per Minute) rating, ideally 7.0 GPM or higher, and a higher BTU output (160,000 BTU or more).
• If you have limited installation space or are looking for maximum flexibility, choose a tankless model that explicitly states it can be installed indoors or outdoors and is compatible with both propane and natural gas.
• If you primarily need hot water for a smaller household or specific applications and are concerned about low-flow efficiency, choose a unit with a lower GPM rating (around 4-5 GPM) and features like low-flow start technology.
• If you want the most powerful and efficient option for a larger home and have the appropriate ventilation, consider a condensing tankless model, which offers higher efficiency.

Quick Best 40 Gallon Propane Water Heater Buying Checklist

• Check Local Codes: Ensure your chosen model meets all local building and venting regulations for propane water heaters.
• Verify Venting Type: Confirm the unit’s venting system (direct, power, or conventional) is compatible with your installation location.
• Consider Recovery Rate: Select a model with a recovery rate that can meet your household’s peak hot water demands.
• Measure Installation Space: Accurately measure the available space, including height, diameter, and clearance requirements.
• Review Energy Factor: Look for a higher Energy Factor (EF) for better long-term operating efficiency.
• Assess Ignition Type: Decide between the convenience of electronic ignition or the simplicity of a pilot light system.

Frequently Asked Questions

What Is The Typical First Hour Rating For A 40 Gallon Propane Water Heater?

A typical 40-gallon propane water heater often features a First Hour Rating (FHR) between 70 and 90 gallons. This measurement indicates how much hot water the unit can supply in the first hour of use, starting with a full tank.

How Does The Recovery Rate Of A Propane Water Heater Affect Performance?

The recovery rate, usually measured in gallons per hour, signifies how quickly the water heater can reheat a full tank. A higher recovery rate ensures that you can replenish hot water faster, which is crucial for households with high demand.

What Is The Difference Between Direct-Vent And Power-Vent Propane Water Heaters?

Direct-vent water heaters draw combustion air from outside and vent exhaust gases directly through a wall, creating a sealed system. Power-vent units use a fan to exhaust gases, offering more flexibility in venting location but requiring a power source.

Are Electronic Ignition Systems More Reliable For Propane Water Heaters?

Electronic ignition systems on propane water heaters often offer greater reliability and convenience than traditional pilot lights. They eliminate the need for a constantly burning pilot, saving gas and reducing potential issues with pilot light outages.

What Are The Crucial Clearance Requirements For Installing A Propane Water Heater?

Proper clearance ensures safe operation and efficient venting for propane water heaters. Always consult the manufacturer’s manual for specific distances required around the unit for airflow and access, typically several inches on all sides and above.

Final Words

Investing in the best 40 gallon propane water heater ensures consistent hot water for your home, offering reliability and efficiency. These units provide a robust solution for various household needs, delivering comfort and convenience. Upgrade your water heating system today for dependable performance.