Best Gas Hot Water Heaters To Buy: Practical Features for Easier Everyday Use

A strong gas hot water heater delivers on-demand water at a flow rate matched to your busiest fixtures, making it suitable for households that want continuous hot water without a storage tank. This roundup compares 10 natural-gas tankless models across indoor and outdoor installation, output from 4.2 to 8.4 GPM, and burner capacity from 95,000 to 199,000 BTU. The practical differences matter: a compact 4.2- to 5.3-GPM unit may suit lighter demand, while larger homes may need 7.0 GPM or more for multiple showers and appliances.

Safety features, venting requirements, freeze protection, controls, heat-exchanger design, and included installation parts also affect fit. Use the sizing and installation guidance below to narrow the list before checking local requirements.

The best choice depends on peak simultaneous demand and installation location. For larger households, the Rheem RTGH Series 8.4 GPM indoor model, Westinghouse 8.1 GPM outdoor model, and GASLAND Gasmart E 7.6 GPM model offer the highest listed flow rates. For moderate demand, ThermoMate’s 5 GPM, APUS’s 4.42 GPM, Heatrova’s 4.3 GPM, or NOVIEEX’s 4.3 GPM units may fit better.

Choose an indoor model when direct venting is workable; choose an outdoor model to avoid indoor venting, subject to climate and installation requirements.

Natural Gas Tankless Water Heater Comparison

Image	Product	Buy
Best Pick 1	ThermoMate CZ422NG, Natural Gas Tankless Water Heater Indoor, Up to 5 GPM Best for: Compact Indoor Heating Brand: thermomate | Capacity: 5 gallons	View on Amazon
Best Pick 2	APUS Natural Gas Tankless Water Heater, 95,000 BTU, 4.42 GPM Indoor Best for: Balanced Flow Rate Brand: APUS | Capacity: 4.42 gallons	View on Amazon
Best Pick 3	GASLAND Gasmart E 199,000 BTU Tankless Water Heater, Up to 7.6 GPM, CSA Certified Whole House Natural Gas Indoor Installation Residential On-demand Instant Hot Water Heater, CE686NG Best for: Whole House Capacity Brand: GASLAND | Capacity: 26 liters	View on Amazon
Best Pick 4	APUS Natural Gas Tankless Water Heater, 140,000 BTU, Up to 6.8 GPM, Indoor Best for: High Flow Rate Brand: APUS | Capacity: 6.8 gallons	View on Amazon
Best Pick 5	Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Outdoor | 160,000 BTUs High Efficiency On Demand, Continuous Hot Water | Non-Condensing Best for: Outdoor Installation Brand: Rheem | Capacity: 7 gallons	View on Amazon

How We Compared These Products

We compared dimensions, capacity, materials, compatibility, included components, and care requirements across many Amazon listings. These details matter because the product must fit the available space, intended use, setup requirements, and maintenance routine. After examining the wider field, we selected 10 products from thermomate, APUS, GASLAND, Rheem, Westinghouse, LiberLive, Heatrova, and NOVIEEX.

The shortlist includes products such as ThermoMate CZ422NG, APUS Natural Gas Tankless Water Heater, and GASLAND Gasmart E Every recommendation is tied to information stated for that specific product; unclear or missing features were treated as unknown rather than filled with assumptions.

Detailed Reviews: Best Gas Hot Water Heaters To Buy

1. ThermoMate CZ422NG, Natural Gas Tankless Water Heater Indoor, Up to 5 GPM

Best for: Compact indoor gas heating.

This ThermoMate tankless water heater offers up to 5 GPM flow rate, ideal for on-demand hot water. Its compact dimensions and included installation kits simplify placement and setup for immediate use. Integrated safety features ensure reliable operation.

With a 5 GPM capacity, this natural gas unit provides continuous hot water for household needs. It features anti-freezing protection, dry combustion protection, and flame failure protection, enhancing its durability and safety. The unit operates on 120 volts, making it compatible with standard electrical setups.

Product Details

Pros

• Up to 5 GPM flow rate
• Compact design
• Includes installation kits
• Multiple safety features

Cons

• 22 pounds item weight

Suitable for smaller homes needing efficient, on-demand hot water. Ensure adequate ventilation and gas line connection for optimal performance and safety.

2. APUS Natural Gas Tankless Water Heater, 95,000 BTU, 4.42 GPM Indoor

Best for: Space-saving natural gas heating.

The APUS Natural Gas Tankless Water Heater delivers 4.42 GPM with a 95,000 BTU output, providing on-demand hot water. Its slim 5.9-inch width allows for flexible installation in tighter spaces, maximizing home utility areas.

This 4.42 GPM unit operates at 95,000 BTU, ensuring a steady supply of hot water for daily use. It requires 120 volts and 35 watts, fitting standard electrical requirements. The included vent pipe and assembly kit facilitate a straightforward installation process.

Product Details

Pros

• 4.42 GPM flow rate
• 95,000 BTU output
• Slim 5.9-inch width
• Includes vent pipe and kit

Cons

• 19.2 pounds item weight

Ideal for apartments or smaller homes prioritizing space efficiency. Verify local venting requirements before installation. Confirm its stated fit, dimensions, compatibility, and included components against the intended setup before choosing it.

3. GASLAND Gasmart E 199,000 BTU Tankless Water Heater, Up to 7.6 GPM, CSA Certified Whole House Natural Gas Indoor Installation Residential On-demand Instant Hot Water Heater, CE686NG

Best for: Whole-house CSA certified heating.

The GASLAND Gasmart CE686NG offers a high capacity of 7.6 GPM, providing unlimited hot water for whole-house residential use. CSA certification ensures it meets rigorous safety standards for reliable operation and peace of mind.

With a 7.6 GPM flow rate and 199,000 BTU, this unit delivers continuous hot water for multiple fixtures simultaneously. It features anti-freezing, dry combustion, and flame failure protections. The compact, wall-mounted design saves significant space compared to traditional tank heaters.

Product Details

Pros

• 7.6 GPM flow rate
• CSA Certified
• Unlimited hot water
• Space-saving design

Cons

• 37.5 pounds item weight

Best for larger homes needing substantial hot water capacity. Ensure proper ventilation and professional installation for this powerful unit.

4. APUS Natural Gas Tankless Water Heater, 140,000 BTU, Up to 6.8 GPM, Indoor

Best for: Instant hot water with zero wait.

This APUS Natural Gas Tankless Water Heater provides instant hot water with its 6.8 GPM flow rate and 140,000 BTU. Featuring exclusive Zero Cold Water Tech, it eliminates the wait for hot water, offering immediate comfort.

The 6.8 GPM capacity and 140,000 BTU output ensure consistent hot water delivery for multiple simultaneous uses. Its oxygen-free copper heat exchanger contributes to durable performance. The unit operates on 120 volts and 44 watts, with included installation accessories.

Product Details

Pros

• 6.8 GPM flow rate
• Zero Cold Water Tech
• 140,000 BTU output
• Oxygen-free copper heat exchanger

Cons

• 26.9 pounds item weight

Ideal for households demanding immediate hot water without delay. Verify installation space and local venting regulations. Confirm its stated fit, dimensions, compatibility, and included components against the intended setup before choosing it.

5. Rheem RTG Series 7.0 GPM Natural Gas Tankless Water Heater Outdoor | 160,000 BTUs High Efficiency On Demand, Continuous Hot Water | Non-Condensing

Best for: Outdoor high-efficiency continuous hot water.

The Rheem RTG Series outdoor tankless water heater delivers 7.0 GPM at a 35°F rise, powered by 160,000 BTUs for continuous hot water. Its non-condensing design and outdoor installation eliminate venting requirements, simplifying setup.

This unit provides 7.0 GPM flow, suitable for 2-3 simultaneous showers, with a 160,000 BTU output. It features Hot Start Programming to minimize cold water bursts and a low activation flow rate. The stainless steel construction ensures durability for outdoor use.

Product Details

Pros

• 7.0 GPM flow rate
• Outdoor installation
• 160,000 BTU output
• Hot Start Programming

Cons

• 39.3 pounds item weight

Perfect for homes needing reliable outdoor hot water supply. Ensure it is installed in a location protected from extreme weather elements.

6. Rheem RTGH Series 8.4 GPM Natural Gas Tankless Water Heater Indoor | 157,000 BTUs Super High Efficiency On Demand, Continuous Hot Water | Condensing Ultra-Low Nox

Best for: Ultra-low NOx condensing whole-house heating.

The Rheem RTGH Series is a super high-efficiency indoor condensing gas tankless water heater providing 8.4 GPM with 157,000 BTUs. Its ultra-low NOx emissions and 0.93 UEF make it an eco-friendly choice for large families.

With an 8.4 GPM capacity at a 35°F rise, this unit supports 3-4 simultaneous showers. It features exclusive Hot Start Programming and an overheat film wrap for safety.

Product Details

Pros

• 8.4 GPM flow rate
• Super High Efficiency (0.93 UEF)
• Ultra-low NOx emissions
• Hot Start Programming

Cons

• 59.9 pounds item weight

Ideal for large, multi-bathroom homes prioritizing energy efficiency and reduced emissions. Requires proper venting for indoor installation. Confirm its stated fit, dimensions, compatibility, and included components against the intended setup before choosing it.

7. Westinghouse Tankless Water Heater Natural Gas Outdoor, CSA Certified

Best for: Outdoor CSA certified precise temperature control.

The Westinghouse tankless water heater is designed for outdoor installation, delivering up to 8.1 GPM and 180,000 BTU for whole-home hot water. Its CSA certification and precise ±1°F temperature stability ensure consistent comfort.

This unit supports 3-5 fixtures simultaneously with its 8.1 GPM flow rate. Advanced self-modulating technology automatically adjusts gas and water flow for consistent temperatures. It operates on 120 volts and 54 watt-hours, suitable for outdoor applications.

Product Details

Pros

• 8.1 GPM flow rate
• CSA Certified
• ±1°F Temperature Stability
• Outdoor installation

Cons

• 17.1"W x 26.8"H dimensions

Best for homes needing robust outdoor hot water delivery with precise temperature control. Ensure adequate clearance and protection from severe weather.

8. Natural Gas Tankless Water Heater, Outdoor Installation, Up to 5.3 GPM 130000 BTU On Demand Residential Natural Gas Instant Hot Water Heater Outdoor with Remote Controller, 110V,CSA Certificated,White

Best for: Space-saving outdoor natural gas heating.

This outdoor tankless water heater from LiberLive provides up to 5.3 GPM with a 130,000 BTU output, offering on-demand hot water while saving indoor space. Its corrosion-resistant body is designed for outdoor durability.

With a 5.3 GPM capacity, this unit is suitable for residential use. It features anti-freezing, dry combustion, and flame failure protections for safe operation. The included remote controller allows for convenient temperature adjustments from inside the home.

Product Details

Pros

• 5.3 GPM flow rate
• Outdoor installation
• 130,000 BTU output
• Includes remote controller

Cons

• 110 volts operation

A good option for homeowners seeking to free up indoor space. Verify local regulations regarding outdoor appliance installation and venting.

9. Natural Gas Tankless Water Heater Indoor,HeatRova 4.3 GPM 102,000 BTU,Instant Hot Water,Constant Temperature,Pure Copper Heat Exchanger,3/4″ NPT Connector,Energy-Saving,On-Demand for 3–4 Fixtures

Best for: Indoor constant temperature pure copper heating.

The Heatrova TGHT002 indoor natural gas tankless water heater delivers 4.3 GPM with 102,000 BTU, providing instant hot water for 3-4 fixtures. Its pure copper heat exchanger and intelligent constant temperature control ensure efficiency and comfort.

This unit offers a 4.3 GPM flow rate, suitable for simultaneous use in showers and kitchens. It features multiple safety protections including abnormal combustion flame protection and anti-scald measures. The 3/4" NPT connector simplifies plumbing connections.

Product Details

Pros

• 4.3 GPM flow rate
• Pure copper heat exchanger
• Constant Temperature PLUS technology
• Multiple safety features

Cons

• 13.7"W x 13.7"H dimensions

Ideal for larger homes needing reliable, on-demand hot water with consistent temperature. Ensure proper indoor venting and gas line compatibility.

10. Natural Gas Tankless Water Heater Up to 4.3 GPM 100,000 BTU, Indoor

Best for: Indoor LED display gas heating.

The NOVIEEX RS-16 tankless water heater provides up to 4.3 GPM with a 100,000 BTU output for indoor natural gas applications. An integrated LED display offers easy monitoring of operating status and temperature.

This unit delivers 4.3 GPM, suitable for multiple fixtures. It includes anti-freezing, dry combustion, and flame failure protections for enhanced safety. Operating on 120 volts, it is designed for straightforward integration into existing home systems.

Product Details

Pros

• 4.3 GPM flow rate
• LED Display
• 100,000 BTU output
• Anti-Freezing Protection

Cons

• 19.8 pounds item weight

Suitable for homes needing a compact, indoor unit with a clear display. Confirm local venting requirements and gas line size.

What Buyers Often Overlook

Sizing by peak demand and flow rate

Match the heater to the combined flow of fixtures you may use at the same time, not to the number of bathrooms alone. The listed models range from 4.2 to 8.4 GPM, giving a useful spread for different demand levels. ThermoMate lists up to 5 GPM, while APUS offers 4.42 GPM and up to 6.8 GPM versions.

Heatrova and NOVIEEX each list about 4.3 GPM. At the larger end, Rheem lists 7.0 GPM outdoors and 8.4 GPM indoors, Westinghouse lists 8.1 GPM, and GASLAND lists up to 7.6 GPM.

Actual simultaneous output also depends on incoming-water temperature and the required temperature rise, so the advertised flow rate is not a guarantee for every climate or fixture combination. Size around the household’s busiest realistic use, such as multiple showers plus laundry or dishwashing.

The Key Product Trade-Off

Indoor versus outdoor installation fit

Indoor and outdoor models solve different installation constraints. Indoor choices in this list include direct-vent or vented designs such as the Rheem RTGH Series, APUS models, Heatrova, NOVIEEX, ThermoMate, and GASLAND. They require a suitable indoor installation location and compatible venting arrangement.

Outdoor choices, including Rheem’s RTG Series, Westinghouse, and LiberLive, place the appliance outside and can avoid indoor venting. That can preserve indoor space, but outdoor exposure makes freeze protection and local climate suitability important; several products list anti-freezing protection.

Installation type is not interchangeable: confirm gas, water, electrical, venting, clearances, and code requirements before choosing. Product dimensions also vary substantially, from compact units such as the 5.9-inch-wide APUS 4.42 GPM model to larger high-output units such as Rheem’s 17.7-inch-wide indoor model.

Best Gas Hot Water Heaters To Buy: Buyer's Guide

Fit, Dimensions, and Compatibility

Compare the listed dimensions with the intended counter, cabinet, appliance, storage, or installation space. Confirm model compatibility and connection requirements where they are supplied. A useful feature cannot compensate for a product that does not physically fit or work with the buyer’s existing setup.

Capacity, Output, and Operating Format

Match listed capacity, volume, output, and operating mode to the actual household or work routine. Larger figures can support heavier use, while a smaller format may be easier to place and maintain. Treat daily output, immediate storage, and container capacity as separate specifications when the listing distinguishes them.

Materials, Construction, and Care

Use the listed materials and care instructions to judge cleaning effort, storage conditions, and compatibility with the intended use. Dishwasher, freezer, food-contact, or weather-related claims are included only when supplied for that product. Check whether routine care fits the way the product will be used.

Included Components and Setup Needs

Review the included components before planning installation or first use. Hoses, adapters, lids, paddles, bowls, brushes, controls, and manuals vary by listing. Confirm power, water, assembly, or accessory requirements from the supplied product information rather than assuming that separately pictured parts are included.

Which Should You Choose?

Choose a 4.2- to 5.3-GPM model for lighter simultaneous demand or a smaller installation footprint: APUS 4.42 GPM, Heatrova 4.3 GPM, NOVIEEX 4.3 GPM, ThermoMate 5 GPM, and LiberLive 5.3 GPM cover that range. Choose 6.8 to 8.4 GPM when multiple showers, laundry, or kitchen fixtures may overlap; APUS 6.8 GPM, GASLAND 7.6 GPM, Westinghouse 8.1 GPM, and Rheem 7.0 or 8.4 GPM models are the stronger capacity matches. Select indoor installation when a compliant venting path is available, or outdoor installation when avoiding indoor venting is the priority.

Favor condensing efficiency and direct venting with Rheem’s RTGH Series, while prioritizing included kits, remote controls, diagnostics, freeze protection, or temperature stability when those features match your installation needs.

Quick Buying Checklist

• Confirm the complete dimensions against the available space.
• Verify model, accessory, connection, and appliance compatibility.
• Match capacity or output to the expected amount of use.
• Compare materials and care instructions with the maintenance routine.
• Check the included components before planning setup or first use.
• Confirm listed power, water, storage, or installation requirements where applicable.

Frequently Asked Questions

What is the main advantage of a tankless water heater?

Tankless water heaters provide continuous hot water on demand, meaning you won’t run out during showers or high usage. They are also more energy-efficient as they only heat water when needed, potentially saving on utility costs compared to traditional tank models.

How do I choose the right GPM for my needs?

GPM (gallons per minute) indicates how much hot water the heater can supply. Consider the number of fixtures you’ll run simultaneously. For a single shower, 2-3 GPM might suffice, while multiple bathrooms and appliances may require 5 GPM or higher.

What is the difference between condensing and non-condensing tankless heaters?

Condensing models recapture heat from exhaust gases, making them more energy-efficient. Non-condensing models vent this heat directly outside.

Can a tankless water heater be installed outdoors?

Yes, many tankless water heaters are designed for outdoor installation, which can save indoor space and simplify venting. Ensure the model is rated for outdoor use and protected from extreme weather conditions to maintain optimal performance and longevity.

What are the benefits of a pure copper heat exchanger?

A pure copper heat exchanger offers superior thermal conductivity, allowing for faster and more efficient heat transfer. This means quicker hot water delivery and potentially better energy efficiency. Copper is also highly resistant to corrosion, contributing to the unit’s durability.

Final Words

Selecting the best natural gas tankless water heater depends on your household’s hot water demands and installation preferences. For whole-house solutions, higher GPM models are ideal. Always match the GPM to your peak usage to ensure consistent hot water.