Best Thermomate Natural Gas Tankless Water Heaters in 2026: 3 Picks

Quick picks

The best fit for you

• You want the most compact model on the list Thermomate 3.06 GPM Natural Gas Tankless Water Heater It weighs only 19.8 pounds and measures 13.8 inches wide.
• You need high-flow hot water for busy households Thermomate 5.28 GPM Indoor Natural Gas Its 5.28 GPM flow rate supports high-volume usage efficiently.
• You require stable heating for a single bathroom Thermomate 98,500 BTU Natural Gas Tankless Water Heater The 98,500 BTU output provides precise temperature control indoors.

Our 3 picks

1 Best overall

Thermomate 3.06 GPM Natural Gas Tankless Water Heater

Best for: single-shower precision and space efficiency

Fuel Type

Natural Gas (what this guide is about)

Flow Rate

Up to 3.06 GPM

BTU

75,000 BTU

Installation Location

Indoor

Voltage

120V

Temperature Control

90–140°F, ±1°F

View on Amazon: Thermomate 3.06 GPM Natural Gas Tankless Water Heater Affiliate link

This indoor unit delivers up to 3.06 GPM of hot water using 75,000 BTU of natural gas. It maintains temperature stability within ±1°F and reaches 98% thermal efficiency. The compact design fits small spaces, and the smart display tracks flow and flame status. It suits single-shower households or kitchen sinks where precise temperature control matters.

Pros

• Up to 3.06 GPM flow rate
• 75,000 BTU/hr heating power
• ±1°F temperature stability
• 98% thermal efficiency
• Compact 21" H x 13" W footprint

Cons

• Lower 3.06 GPM flow rate compared to 5.28 GPM competitors
• Indoor installation only
• Requires 120V electrical connection

Good fit if

• You need precise temperature control for a single shower
• You have limited indoor space for installation
• You want high thermal efficiency for energy savings

Skip if

• You require high flow rates for multiple simultaneous showers
• You need outdoor installation capability
• You prefer a larger capacity unit for whole-house use

Verdict: ThermoMate 3.06 GPM Natural Gas Heater offers precise temperature control and high efficiency for single-shower needs, making it ideal for small households or kitchen applications where space and stability are priorities.

2 Best premium

Thermomate 5.28 GPM Indoor Natural Gas

Best for: High-flow households seeking maximum efficiency

Fuel Type

Natural Gas (what this guide is about)

Flow Rate

Up to 6 GPM

BTU

114,000 BTU

Installation Location

Indoor

Voltage

120V

Temperature Control

90°F to 140°F

View on Amazon: Thermomate 5.28 GPM Indoor Natural Gas Affiliate link

This ThermoMate natural gas tankless water heater delivers up to 5.28 GPM with 114,000 BTU of heating power. Its condensing design achieves 0.86 UEF efficiency through a dual heat exchanger. The unit features a 3.5-inch LED touchscreen for precise temperature control between 90°F and 140°F. It includes eight safety protections and auto-frost prevention. This indoor model suits busy households needing simultaneous hot water for multiple fixtures.

Pros

• 114,000 BTU/hr output supports up to 5.28 GPM flow rate
• 0.86 UEF efficiency with dual stainless steel and copper heat exchangers
• 3.5-inch LED touchscreen displays real-time flow and error codes
• Eight integrated safety protections including boil-dry and freeze prevention

Cons

• Produces mildly acidic condensate requiring a neutralizer kit
• Heavier at 26 pounds compared to non-condensing models
• Requires external condensate drainage installation

Good fit if

• You need high flow rates for multiple simultaneous showers
• You want maximum energy efficiency with a condensing unit
• You prefer digital monitoring via an integrated touchscreen

Skip if

• You cannot install a condensate neutralizer or drainage line
• You prefer a lighter unit for easy wall mounting
• You are installing in a location without proper venting

Verdict: ThermoMate 114k BTU Condensing Unit offers robust performance for homes needing high-volume hot water. Its advanced efficiency and digital controls make it ideal for busy households willing to manage condensate drainage.

3 Best budget

Thermomate 98,500 BTU Natural Gas Tankless Water Heater

Best for: indoor single-bathroom natural gas heating

Fuel Type

Natural Gas (what this guide is about)

Flow Rate

Up to 4 GPM

BTU

98,500 BTU

Installation Location

Indoor

Voltage

120V

Temperature Control

±1°F

View on Amazon: Thermomate 98,500 BTU Natural Gas Tankless Water Heater Affiliate link

This ThermoMate unit delivers up to 4 GPM of hot water using 98,500 BTU of natural gas power. It features a copper heat exchanger with 98% thermal efficiency and maintains temperature stability within ±1°F. The compact design measures 21.7 inches in height and fits indoor spaces. It includes extensive safety protections and standard 3/4-inch water connections. This model suits households needing reliable indoor heating for one shower and one faucet simultaneously.

Pros

• 98,500 BTU/hr output supports up to 4 GPM flow
• 98% thermal efficiency with 0.81 UEF rating
• Precise temperature control within ±1°F stability
• CSA certified with multiple safety protections
• Compact 21.7" H x 13.8" W x 13.8" D size

Cons

• Limited to indoor installation only
• Requires specific 3" OD venting
• Single unit capacity for one shower and one faucet

Good fit if

• You need a compact indoor unit for a bathroom or utility room
• You want precise temperature control within ±1°F
• You prefer natural gas with high thermal efficiency

Skip if

• You require outdoor installation capability
• You need simultaneous hot water for multiple showers
• You prefer electric power sources over natural gas

Verdict: ThermoMate 98,500 BTU Indoor Natural Gas Heater provides stable hot water for single-bathroom homes. Its compact indoor design and precise temperature control make it ideal for households prioritizing efficiency and safety.

Specifications side by side

How to choose the right one

1. Check indoor suitability

   Verify your installation location matches the unit's rating. The Thermomate 98,500 BTU model is explicitly rated for indoor use. This designation ensures safe operation within enclosed spaces like basements or utility rooms. Other models may require outdoor placement or specific venting configurations. Always confirm the installation location specification before purchasing. Using an indoor-rated unit in an inappropriate space can void warranties or create safety hazards. Match the spec to your physical space constraints to ensure proper fit and compliance.

2. Assess venting requirements

   Identify the venting type required for your home. The 5.28 GPM model is a condensing unit, which typically offers higher efficiency but requires specific condensate drainage management. Condensing units often use different venting materials than standard non-condensing heaters. If you prefer a simpler setup, check if the model requires complex drainage systems. The 3.06 GPM and 98,500 BTU models do not list condensing attributes. Understanding venting needs helps you plan the installation correctly and avoid unexpected modifications to your existing gas lines or exhaust systems.

3. Match flow rate to usage

   Select a flow rate that matches your peak hot water demand. The 3.06 GPM unit is designed for single-shower precision or kitchen sinks. It may struggle if multiple fixtures run simultaneously. The 5.28 GPM model supports high-flow households with greater volume. The 98,500 BTU version targets single-bathroom needs. Consider how many showers or taps you might use at once. Choosing a unit with insufficient flow rate leads to lukewarm water during peak usage. Align the GPM spec with your household's simultaneous fixture count for consistent performance.

4. Evaluate physical dimensions

   Measure your installation space against the unit's dimensions. All three Thermomate models share a width and length of 13.8 inches. However, heights and weights vary. The 3.06 GPM model weighs 19.8 pounds, while the 5.28 GPM unit weighs 26 pounds. The 98,500 BTU model weighs 21.2 pounds. Ensure your mounting area can support the weight and accommodate the height. Compact dimensions make these units suitable for small closets or tight corners. Verify clearances for maintenance access and proper airflow around the unit to ensure safe operation.

5. Confirm fuel compatibility

   Ensure your home supplies natural gas, as all listed models require this fuel type. None of the Thermomate units on this list are designed for propane or electric use. Using the wrong fuel type can damage the unit and create dangerous conditions. Verify your existing gas line pressure and connection type. These units are built specifically for natural gas combustion. If you currently use propane, you will need to adjust your supply or select a different model. Confirming fuel compatibility is the first step in selecting a safe and functional tankless water heater.

Frequently asked questions

See also

• best thermomate tankless water heaters under 300
• best thermomate 240V tankless water heaters
• best natural gas tankless water heaters
• best natural gas garage heaters