7 Best Tankless Water Heaters with 150,000 BTU, Compared

Quick picks

The best fit for you

• You want the best overall indoor natural gas unit GASLAND Gasmart E Indoor Natural Gas Tankless Heater It balances 150,000 BTU input with 5.8 GPM capacity for whole-house use.
• You need the most budget-friendly indoor propane option Camplux 6.4 GPM Indoor Propane Tankless Water Heater This model offers 150,000 BTU heating and 6.4 GPM flow for liquid propane.
• You prefer quiet operation for indoor natural gas setups Camplux 6 GPM Natural Gas Indoor Water Heater It runs at 45 dB with 95% efficiency and 150,000 BTU capacity.
• You want the most compact unit for indoor propane GASLAND Gasmart E 5.8 GPM Indoor Propane Heater It delivers 150,000 BTU and 5.8 GPM in a small, wall-mounted design.
• You need the absolute smallest footprint for natural gas GASLAND Gasmart C 150,000 BTU Natural Gas Heater Its 3.54-inch width is the slimmest profile while providing 150,000 BTU.

Our 7 picks

1 Best overall

GASLAND Gasmart E Indoor Natural Gas Tankless Heater

Best for: indoor whole-home natural gas water heating

BTU

150,000 BTU (what this guide is about)

Fuel Type

Natural Gas

Installation Location

Indoor

Use

Whole House

Dimensions

14.3 × 14.3 × 24.7 inches

Weight

33.1 pounds

View on Amazon: GASLAND Gasmart E Indoor Natural Gas Tankless Heater

This indoor natural gas tankless water heater delivers up to 150,000 BTU and a flow rate of 5.8 GPM for whole-house use. It features an energy factor of 0.8 UEF, wall-mount installation, and built-in freeze and overheat protection. If you need continuous hot water from a compact 33.1-pound indoor unit connected to your natural gas supply line, this model gives you steady multi-fixture output.

Pros

• Delivers up to 5.8 GPM flow rate at 150,000 BTU
• Energy efficiency rating of 0.8 UEF
• Built-in freeze, overheat, and flame-out protection
• Compact 33.1-pound wall-mount indoor footprint

Cons

• Requires a natural gas line rather than liquid propane
• Indoor installation only, not rated for outdoor mounting

Good fit if

• You have an indoor natural gas supply line ready for installation.
• You need up to 5.8 GPM to supply hot water across whole-house fixtures.

Skip if

• You need an outdoor-mounted tankless unit.
• You use liquid propane instead of natural gas.

Verdict: GASLAND Gasmart E Indoor Natural Gas Tankless Heater balances a 150,000 BTU input with a 5.8 GPM capacity for indoor whole-house demands. Its 0.8 UEF rating and wall-mounted build make it a dependable fit for natural gas households.

2 Best budget

Camplux 6.4 GPM Indoor Propane Tankless Water Heater

Best for: indoor whole-home liquid propane setups

BTU

150,000 BTU (what this guide is about)

Fuel Type

Liquid Propane

Flow Rate

Up to 6.4 GPM

Installation Location

Indoor

Temperature Control

±1°F

Certification

CSA

View on Amazon: Camplux 6.4 GPM Indoor Propane Tankless Water Heater

This Camplux indoor tankless water heater runs on liquid propane and delivers 150,000 BTU with flow rates up to 6.4 GPM. It features an oxygen-free copper heat exchanger, a 2.76-inch flue connection, and standard 3/4-inch NPT gas and water fittings. If you need whole-house propane heating for up to three bathrooms indoors while maintaining temperature stability within 1°F, this CSA-certified unit fits your setup.

Pros

• Up to 6.4 GPM water flow rate
• Built-in carbon monoxide detector and CSA certification
• Oxygen-free copper heat exchanger
• Water flow sensor maintains temperature within ±1°F

Cons

• Requires a 2.76-inch flue pipe for indoor venting
• Configured strictly for liquid propane supply lines

Good fit if

• You run your household fixtures on liquid propane fuel.
• You need an indoor unit supporting up to 6.4 GPM flow.
• You have existing 3/4-inch NPT plumbing and gas connections.

Skip if

• You use natural gas rather than liquid propane.
• You plan to mount your water heater outdoors without venting.

Verdict: Camplux Indoor Propane Tankless Water Heater provides 150,000 BTU of on-demand heating and up to 6.4 GPM for homes using liquid propane. Its indoor wall-mount design and integrated safety sensors make it a dependable option for multi-fixture demand.

3 Also great

Camplux Outdoor Propane 6.4 GPM Water Heater

Best for: Outdoor propane installations running multiple fixtures

BTU

150,000 BTU (what this guide is about)

Fuel Type

Propane

Flow Rate

Up to 6.4 GPM

Installation Location

Outdoor

Temperature Control

±1°F

Certification

CSA

View on Amazon: Camplux Outdoor Propane 6.4 GPM Water Heater

This Camplux tankless water heater burns liquid propane to output 150,000 BTU and up to 6.4 GPM of hot water. Designed strictly for outdoor mounting, it requires no indoor venting infrastructure and connects directly via standard 3/4-inch NPT fittings. Its smart gas proportional valve maintains output within 1°F of your target. It fits your home if you need reliable outdoor capacity for three to five simultaneous fixtures.

Pros

• Delivers up to 6.4 GPM with 150,000 BTU heating capacity
• Outdoor wall installation eliminates indoor exhaust venting requirements
• Gas proportional valve regulates temperature within plus or minus 1°F
• Uses standard 3/4-inch NPT gas and water connections
• Built-in freeze, overheat, dry-fire, and flame failure protections

Cons

• Limited to outdoor installation locations only
• Operates exclusively on liquid propane, not natural gas
• Requires 65°F inlet water to reach maximum specified output temperatures

Good fit if

• You have an exterior mounting location and want to avoid indoor venting runs.
• You use liquid propane and require water for up to five fixtures.
• You want consistent water temperature maintained within 1°F.

Skip if

• You need an indoor-mounted water heater.
• You use natural gas instead of liquid propane tanks.

Verdict: Camplux Outdoor Propane 6.4 GPM Water Heater delivers high-volume 150,000 BTU heating for homes utilizing liquid propane. Its outdoor-only design eliminates indoor vent pipe requirements while maintaining water temperatures within 1°F.

4 Best premium

Camplux 6 GPM Natural Gas Indoor Water Heater

Best for: quiet indoor natural gas installations

BTU

150,000 BTU (what this guide is about)

Fuel Type

Natural Gas

Flow Rate

Up to 6 GPM

Installation Location

Indoor

Temperature Control

±0.5°C

Dimensions

14.3 x 14.3 x 6.5 inches

View on Amazon: Camplux 6 GPM Natural Gas Indoor Water Heater

This indoor tankless water heater burns natural gas to supply up to 6 GPM using 150,000 BTU. It features a 95% efficiency rating, a 45 dB bottom-fan design, and temperature stability within ±0.5°C. At 14.3 by 14.3 by 6.5 inches, it offers a compact wall profile. If you have an indoor natural gas hookup and need steady hot water across multiple fixtures, this unit fits your home.

Pros

• Delivers up to 6 GPM with a 150,000 BTU input
• Low sound profile rated at 45 dB
• Temperature stability controlled within ±0.5°C
• High thermal efficiency rated at 95%

Cons

• Requires indoor exhaust through a 2.95-inch vent line
• Configured only for natural gas rather than liquid propane

Good fit if

• You have a natural gas supply and need an indoor installation.
• You want a low operating sound level of 45 dB.
• You need up to 6 GPM to run multiple indoor fixtures.

Skip if

• You use liquid propane for your home fuel source.
• You plan an outdoor installation to avoid venting work.

Verdict: Camplux 6 GPM Indoor Natural Gas Tankless Water Heater delivers 150,000 BTU heating capacity with 95% efficiency and quiet 45 dB operation. It is a solid indoor solution for homes with natural gas connections needing precise temperature stability.

5 Also great

GASLAND Gasmart E 5.8 GPM Indoor Propane Heater

Best for: indoor whole-home liquid propane setups

BTU

150,000 BTU (what this guide is about)

Fuel Type

Propane

Installation Location

Indoor

Use

Whole House

Dimensions

14.3 × 14.3 × 24.7 inches

Weight

33.1 pounds

View on Amazon: GASLAND Gasmart E 5.8 GPM Indoor Propane Heater

The GASLAND Gasmart E is an indoor, propane-fired tankless water heater rated at 150,000 BTU with a maximum flow rate of 5.8 GPM. It delivers an 0.8 UEF rating and mounts directly to an interior wall with a 33.1-pound, 24.7-inch-tall chassis. If you run multiple fixtures on liquid propane and need whole-house capacity inside your utility space, this unit fits your heating demands.

Pros

• Delivers up to 5.8 GPM flow rate at 150,000 BTU
• Energy-efficient 0.8 Uniform Energy Factor (UEF) rating
• Built-in freeze, overheat, and flame-out safety protections
• CSA certified for whole-house indoor wall installation

Cons

• Configured strictly for liquid propane fuel
• Requires indoor installation with dedicated venting space
• Listed warranty coverage limited to one year

Good fit if

• You run your household hot water on a dedicated liquid propane supply.
• You need up to 5.8 GPM of continuous flow for indoor fixtures.
• You want a compact wall-mounted unit weighing under 35 pounds.

Skip if

• You need a natural gas connection rather than propane.
• You plan to mount your water heater outdoors.

Verdict: GASLAND Gasmart E Propane Indoor Water Heater delivers 150,000 BTU and up to 5.8 GPM with an efficient 0.8 UEF rating. It offers reliable, space-saving indoor performance for homes plumbed for liquid propane.

6 Also great

Camplux Climatech 5 Outdoor Natural Gas Water Heater

Best for: outdoor natural gas setups needing multi-fixture flow

BTU

150,000 BTU (what this guide is about)

Fuel Type

Natural Gas

Flow Rate

5.28 GPM

Installation Location

Outdoor

Temperature Control

±1°F

Certification

CSA

View on Amazon: Camplux Climatech 5 Outdoor Natural Gas Water Heater

This is an outdoor natural gas tankless water heater producing 150,000 BTU with a 5.28 GPM flow rate. It features temperature regulation within plus or minus 1 degree Fahrenheit and CSA certification. At 35.3 pounds and measuring 28.4 by 16.9 by 16.9 inches, you mount it outdoors to supply two to three fixtures at once. It suits you if you need exterior natural gas installation without indoor venting.

Pros

• Delivers 150,000 BTU output with a 5.28 GPM flow rate
• Maintains temperature control within 1°F fluctuations
• CSA certified for standard safety requirements
• Outdoor installation eliminates the need for indoor exhaust venting

Cons

• Outdoor installation only
• Requires a dedicated natural gas supply line

Good fit if

• You want an exterior-mounted natural gas heater that saves indoor space.
• You need sufficient hot water flow for two to three simultaneous fixtures.
• You prefer tight temperature control with minimal fluctuation.

Skip if

• You require an indoor water heater installation.
• You use liquid propane instead of natural gas.

Verdict: Camplux 5.28 GPM Outdoor Natural Gas provides 150,000 BTU of exterior heating performance with stable water temperatures for up to three fixtures. It is a solid choice if you want to avoid routing indoor exhaust vents.

7 Also great

GASLAND Gasmart C 150,000 BTU Natural Gas Heater

Best for: compact whole-house natural gas setups

BTU

150,000 BTU (what this guide is about)

Fuel Type

Natural Gas

Flow Rate

5.8 GPM

Dimensions

23.3 x 3.54 x 3.54 inches

Use

Whole House

View on Amazon: GASLAND Gasmart C 150,000 BTU Natural Gas Heater

The GASLAND Gasmart C is a whole-house natural gas tankless water heater delivering up to 5.8 GPM with a 150,000 BTU heat output. It features a 0.8 UEF rating and mounts directly to your wall with compact dimensions measuring 23.3 by 3.54 by 3.54 inches. This unit suits you if you need continuous hot water across household fixtures while running on standard natural gas connections.

Pros

• Delivers up to 5.8 GPM flow rate on natural gas
• Provides 150,000 BTU heating capacity with a 0.8 UEF rating
• Compact wall-mount footprint measuring 23.3 x 3.54 x 3.54 inches
• Backed by a 1-year free replacement warranty

Cons

• Maximum flow rate caps at 5.8 GPM
• Warranty replacement coverage covers only one year

Good fit if

• You need a natural gas tankless water heater rated at 150,000 BTU.
• You have limited wall depth and require a compact 3.54-inch profile.
• You require up to 5.8 GPM of continuous hot water output.

Skip if

• You use liquid propane rather than natural gas.
• You require a flow rate greater than 5.8 GPM.

Verdict: GASLAND Gasmart C 5.8 GPM Natural Gas Tankless Heater delivers 150,000 BTU and a 0.8 UEF rating in an ultra-slim wall-mounted footprint. It provides reliable on-demand hot water for natural gas homes that need up to 5.8 GPM.

Specifications side by side

Is 150,000 BTU the Right Input for You?

A 150,000 BTU input provides the thermal power needed for whole-home demand. This rating supports flow rates between 5.28 and 6.4 GPM, allowing multiple fixtures to run simultaneously. Higher BTU ensures water stays hot during peak usage. If your home has standard gas lines and needs high volume, this input level delivers consistent performance. It is the standard for powerful indoor and outdoor tankless units.

Worth it if

• You need hot water for multiple bathrooms at once
• You want whole-house capacity with natural gas or propane
• You require high flow rates for large showers

Skip it if

• You only need hot water for a single sink
• You have limited gas line capacity or small pipes
• You prefer smaller, low-output units for point-of-use

How we picked these heaters

We selected models from Amazon listings that explicitly state 150,000 BTU in the title or feature list. This input level ensures sufficient heating power for whole-home applications. We only included one size or variant per product family to keep the comparison clear. All details come directly from the published specifications on the listings. We do not physically handle these units. You can rely on the data provided by the manufacturers for accuracy.

The products are ordered by availability first. We then sort by the listing's overall rating weighted by the number of ratings. Finally, we consider how many of our specific criteria the specs meet. This method prioritizes popular, well-reviewed options that match your power requirements. We do not test products ourselves. The ranking reflects current market data and published features only.

How to choose the right one

1. Match fuel to your lines

   You must select the fuel type that matches your existing home infrastructure. Natural gas units, such as the GASLAND Gasmart E, connect directly to standard utility lines. Propane models, like the Camplux Indoor Propane, require liquid propane tanks or a dedicated tank setup. Choosing the wrong fuel type means the unit will not function. Verify your current gas supply before purchasing to ensure compatibility with the heater's input requirements.

2. Check installation location needs

   Decide if you need an indoor or outdoor unit based on your space. Indoor models, including the GASLAND Gasmart E and Camplux Indoor Natural Gas, require proper venting to exhaust combustion gases safely outside. Outdoor units, such as the Camplux Outdoor Propane, eliminate the need for complex indoor vent pipes. If you are installing in a garage or basement, ensure the unit is rated for indoor use. Outdoor models are not suitable for enclosed spaces due to safety risks.

3. Verify whole-house capacity

   Confirm that the heater supports whole-house usage if you intend to supply hot water to multiple fixtures simultaneously. The GASLAND Gasmart E Indoor Natural Gas Heater offers 5.8 GPM capacity, which is sufficient for typical whole-home demands. The Camplux Indoor Propane model provides up to 6.4 GPM. Ensure the flow rate meets your peak usage needs. If you only need hot water for a single bathroom, a lower capacity unit might suffice, but these 150,000 BTU models are designed for broader coverage.

4. Consider physical dimensions

   Measure your installation space carefully, as wall-mounted units vary in size. The GASLAND Gasmart C is ultra-slim at 3.54 inches wide, making it ideal for tight spaces. In contrast, the Camplux Climatech Outdoor Natural Gas unit is larger at 16.9 inches wide and 28.4 inches tall. Check the width, height, and length specifications before mounting. Ensure you have adequate clearance for maintenance access and proper ventilation around the unit to prevent overheating or obstruction.

5. Review efficiency ratings

   Look at the Uniform Energy Factor (UEF) or efficiency percentage to understand operating costs. The GASLAND Gasmart E Indoor Natural Gas Heater has a 0.8 UEF rating, indicating steady efficiency for natural gas operation. The Camplux 6 GPM Indoor Natural Gas model boasts 95% efficiency, which suggests effective heat transfer. Higher efficiency means less wasted energy. Compare these ratings to estimate long-term performance, though actual costs depend on local gas prices and usage patterns.

Frequently asked questions

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• best tankless water heaters under 150
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