Thermomate 98 Alternatives: 6 Similar Picks Compared

How these models compare

Ranein 4.3 GPM Indoor Propane Tankless Water Heater

The Ranein unit offers a slightly higher flow rate of 4.3 GPM compared to the ThermoMate’s 4 GPM. It also provides 100,000 BTU of heating power, which is marginally stronger than the ThermoMate’s 98,500 BTU. This makes it better for households needing consistent hot water for multiple fixtures simultaneously. The Ranein includes preset modes and venting components, simplifying the indoor installation process. However, it is slightly larger and heavier than the compact ThermoMate. If you prioritize maximum flow and included accessories over the ThermoMate’s precise ±1°F temperature stability, this premium option is a practical choice for indoor multi-point use.

VEVOR 4.3 Gal Propane Tankless Water Heater

The VEVOR model matches the ThermoMate in flow rate at 4.3 GPM and shares the same 100,000 BTU heating capacity. It is designed for whole-house use with robust safety features similar to the ThermoMate’s extensive protection list. The VEVOR is identical in dimensions and weight to the ThermoMate, making it a direct physical replacement. It focuses on precision control and reliable instant hot water rather than high-volume simultaneous usage. If you want a budget-friendly indoor propane heater with comparable specs and whole-house capabilities, the VEVOR is a solid alternative. It gives up the ThermoMate’s specific smart diagnostic display but maintains core performance and safety standards for everyday household needs.

APUS 95,000 BTU 4.42 GPM Indoor Propane Heater

The APUS 95,000 BTU model offers a higher flow rate of 4.42 GPM than the ThermoMate’s 4 GPM. It provides precise temperature control and quiet operation, appealing to users who value steady water temperatures. This unit is significantly narrower at 5.9 inches wide compared to the ThermoMate’s 13.8-inch width, saving more wall space. It features a digital interface for easy monitoring. However, it lacks the explicit ±1°F stability claim and the comprehensive safety certifications listed for the ThermoMate. If you need a compact, quiet indoor heater with slightly higher flow and a digital display, this APUS model is a strong alternative to the ThermoMate’s broader feature set.

APUS 140,000 BTU Indoor Propane Tankless Water Heater

The APUS 140,000 BTU model is a high-capacity unit designed for large households. It includes a booster pump for consistent flow and smart app control, features absent in the ThermoMate. This unit is narrower at 7.09 inches wide but heavier at 26.9 pounds. It offers precise temperature settings for whole-home hot water demands. The ThermoMate is better for smaller spaces and basic indoor use without smart connectivity. If you need high flow, smart monitoring, and powerful heating for a large home, this APUS model is superior. It gives up the ThermoMate’s simplicity and lower weight for advanced connectivity and higher performance.

Rinnai 8.5 GPM Indoor Propane Tankless Water Heater

The Rinnai RE180iP offers a significantly higher flow rate of 8.5 GPM, making it suitable for homes with up to seven fixtures. It is a non-condensing unit, differing from the ThermoMate’s efficiency design. The Rinnai is larger, measuring 27.3 inches in height and weighing 53.8 pounds. It prioritizes durability and high capacity over built-in smart features. The ThermoMate is more compact and energy-efficient for single-point or small household use. If you need high-flow indoor propane heating for a large family and value durability, the Rinnai is the better choice. It sacrifices the ThermoMate’s compact size and precise digital control for raw capacity and robust construction.

MIZUDO 10.3 GPM Propane Tankless Heater

The MIZUDO 199,000 BTU model provides a massive 10.3 GPM flow rate, far exceeding the ThermoMate’s 4 GPM. It is designed for large households with high hot water demands. This unit includes smart connectivity and precise temperature control. It is larger and heavier than the ThermoMate, measuring 24.8 inches in height. The ThermoMate is better for smaller spaces and moderate usage. If you need maximum flow and smart features for a large home, the MIZUDO is ideal. It gives up the ThermoMate’s compact form factor and lower power consumption for high-volume performance and advanced monitoring capabilities.

Quick picks

Our 7 picks

1 Best overall

ThermoMate 4 GPM Propane Tankless Water Heater

Best for: Indoor propane users needing precise temp control

Fuel Type

Propane

Flow Rate

Up to 4 GPM

BTU

98,500 BTU

Installation Location

Indoor

Voltage

120V

Temperature Control

90–140°F, ±1°F

View on Amazon: ThermoMate 4 GPM Propane Tankless Water Heater

The Thermomate delivers up to 4 GPM at 98,500 BTU for indoor propane use. It features a copper heat exchanger with 98% thermal efficiency and precise temperature control within ±1°F. The compact 21.7-inch unit includes a smart LED display and multiple safety protections. It suits households needing reliable, space-saving hot water for one shower and one faucet simultaneously.

Pros

• 98,500 BTU output supports 4 GPM flow
• 98% thermal efficiency with copper heat exchanger
• Precise temperature control within ±1°F stability
• Multiple safety protections including freeze and boil-dry

Cons

• Lower flow rate compared to 6.8 GPM competitors
• Heavier at 21.2 pounds than some alternatives
• Indoor installation only, no outdoor rating

Good fit if

• You need a compact indoor propane heater
• You want precise temperature stability within ±1°F
• You require high thermal efficiency for cost savings

Skip if

• You need outdoor installation capability
• You require more than 4 GPM flow
• You prefer natural gas over propane fuel

Verdict: Thermomate 98,500 BTU Propane Tankless Heater is ideal for users prioritizing precise temperature control and energy efficiency in a compact indoor unit. It fits homes needing reliable hot water for single-point use without demanding high-volume flow.

2 Best premium

Ranein 4.3 GPM Indoor Propane Tankless Water Heater

Best for: Indoor multi-point high flow needs

Fuel Type

Propane Gas

Flow Rate

4.3 GPM

BTU

100,000 BTU

Installation Location

Indoor

Temperature Control

95°F-155°F

Use

Whole House

View on Amazon: Ranein 4.3 GPM Indoor Propane Tankless Water Heater

The Ranein 100,000 BTU propane tankless water heater delivers 4.3 GPM for indoor use. It features an oxygen-free copper heat exchanger and four preset modes for kitchen, shower, bathtub, and seasonal adjustments. The unit includes an LED display with temperature memory and operates within a 95°F to 155°F range. It also offers anti-freeze protection down to 14°F and comes with a vent pipe for installation.

Pros

• 100,000 BTU output supports 3-4 water points simultaneously
• 4.3 GPM flow rate for continuous hot water
• Oxygen-free copper heat exchanger for durability
• Four intelligent preset modes for different uses
• Includes vent pipe for indoor installation

Cons

• Indoor installation only, not suitable for outdoor use
• Not recommended for elevations above 2,000 feet
• Requires professional installation by a licensed technician

Good fit if

• You need high output for multiple simultaneous water points
• You want preset modes for different water uses
• You prefer indoor installation with included venting

Skip if

• You require outdoor installation capabilities
• You live at an elevation above 2,000 feet
• You prefer DIY installation without professional help

Verdict: Ranein 100k BTU Propane Tankless Heater suits households needing high flow rates for multiple fixtures. It is ideal for indoor setups where preset modes and included venting simplify installation and operation.

3 Best budget

VEVOR 4.3 Gal Propane Tankless Water Heater

Best for: Indoor whole-house propane heating with precision control

Fuel Type

Propane

BTU

100,000 BTU/h

Installation Location

Indoor

Temperature Control

±1°F

Dimensions

21.7 x 13.8 x 13.8 inches

Use

Whole House

View on Amazon: VEVOR 4.3 Gal Propane Tankless Water Heater

This VEVOR propane tankless water heater delivers 100,000 BTU/h with a 4.3 GPM flow rate. It features ±1°F precision temperature control and an LED display for easy monitoring. Designed for indoor whole-house use, it includes multiple safety protections against overheating and leaks. The unit connects via standard 1/2 inch NPT fittings. It suits households seeking reliable instant hot water with consistent temperature stability.

Pros

• 100,000 BTU/h heating capacity
• 4.3 GPM flow rate
• ±1°F temperature precision
• LED display with touch controls
• Multiple safety protections included

Cons

• 4.3 GPM may limit simultaneous use in large homes
• Heavier at 19.8 pounds
• No remote control or app mentioned

Good fit if

• You need a propane unit for indoor installation
• You want precise temperature stability within ±1°F
• You prefer a unit with an LED display

Skip if

• You require a flow rate above 4.3 GPM
• You need a natural gas model
• You want a lighter unit under 20 pounds

Verdict: VEVOR 4.3 Gal 100K BTU Propane Heater offers stable temperature control and robust safety features for indoor whole-house use. It fits buyers who prioritize precision and reliable instant hot water over high-volume simultaneous usage.

4 Also great

APUS 95,000 BTU 4.42 GPM Indoor Propane Heater

Best for: Indoor households needing precise temperature stability

Fuel Type

Propane

Flow Rate

4.42 GPM

BTU

95,000 BTU

Installation Location

Indoor

Voltage

120 V

Temperature Control

95°F–140°F, ±1°F

View on Amazon: APUS 95,000 BTU 4.42 GPM Indoor Propane Heater

The APUS 95,000 BTU propane tankless water heater delivers 4.42 GPM for indoor use. It maintains temperature within ±1°F using smart CPU control and features an LED touchscreen. The unit measures 20.55 x 13.27 x 5.91 inches and operates at 36dB. It includes built-in freeze protection and oxygen-free copper heat exchangers for 98% thermal efficiency. This model suits homes needing steady hot water for multiple fixtures.

Pros

• 95,000 BTU heating capacity supports up to 4.42 GPM flow
• Temperature control stays within ±1°F of the set point
• LED touchscreen interface for intuitive adjustment
• Quiet operation at 36dB during use

Cons

• 2-year warranty is shorter than the 5-year standard in this category
• Indoor-only installation limits placement options
• Requires 120V AC power connection for operation

Good fit if

• You need precise temperature stability for multiple simultaneous showers
• You prefer an LED display over manual dials
• You require a compact unit for indoor installation

Skip if

• You need outdoor installation capability
• You require a warranty longer than 2 years
• You prefer natural gas over propane fuel

Verdict: APUS 95K BTU Propane Tankless Heater offers precise temperature control and quiet operation for indoor households. It fits buyers who prioritize steady water temperature and a digital interface over long-term warranty coverage.

5 Also great

APUS 140,000 BTU Indoor Propane Tankless Water Heater

Best for: Whole-home hot water with smart app control

Fuel Type

Propane

Flow Rate

Up to 6.8 GPM

BTU

140,000 BTU

Installation Location

Indoor

Voltage

120V AC

Temperature Control

95–140°F, ±1°F

View on Amazon: APUS 140,000 BTU Indoor Propane Tankless Water Heater

The APUS 140,000 BTU propane tankless water heater delivers up to 6.8 GPM for whole-home use. It features a built-in booster pump and smart seasonal comfort control with ±1°F accuracy. The unit includes zero cold water tech and an LED display. It requires 120V AC power and standard 1/2" NPT connections for indoor installation.

Pros

• 140,000 BTU output with 6.8 GPM flow rate
• Built-in booster pump increases flow by up to 130%
• Smart seasonal comfort with ±1°F temperature precision
• Tuya app control for remote monitoring and preheating

Cons

• Requires 120V AC electrical connection for operation
• Indoor installation only
• Mandatory draining in freezing conditions to prevent damage

Good fit if

• You need high flow rates for multiple simultaneous showers
• You want precise temperature control via a mobile app
• You have an indoor space with 120V AC access

Skip if

• You require outdoor installation capabilities
• You need a unit that operates without electricity
• You live in a climate with freezing ambient temperatures without drainage plans

Verdict: APUS 140k BTU Propane Tankless Heater suits large households needing high flow and smart control. It delivers consistent hot water through its booster pump and precise temperature settings.

6 Best non-condensing

Rinnai 8.5 GPM Indoor Propane Tankless Water Heater

Best for: high-flow indoor propane needs

Fuel Type

Propane

Flow Rate

8.5 GPM

BTU

180k BTU

Installation Location

Indoor

Dimensions

27.3 x 14.1 x 10.8 inches

Venting Type

Non-Condensing

View on Amazon: Rinnai 8.5 GPM Indoor Propane Tankless Water Heater

The Rinnai RE180iP is a non-condensing propane tankless water heater designed for indoor installation. It delivers up to 8.5 GPM, supporting seven simultaneous fixtures. Its compact dimensions of 27.3 by 14.1 by 10.8 inches allow it to fit in tight spaces. The unit weighs 53.8 pounds and features an LED screen for error codes. It includes a 15-year heat exchanger warranty, making it a durable option for high-demand households.

Pros

• High flow rate of 8.5 GPM for multiple fixtures
• Compact indoor footprint suitable for small spaces
• 15-year limited warranty on the heat exchanger
• LED screen displays service reminders and error codes

Cons

• Requires professional installation and does not include WiFi control module
• Non-condensing design may be less efficient than condensing models
• Labor warranty drops to 1 year if not registered within 90 days

Good fit if

• You need a high-flow indoor propane unit for multiple bathrooms
• You have limited space for a compact tankless heater
• You prefer a durable unit with a long heat exchanger warranty

Skip if

• You require outdoor installation capabilities
• You want built-in WiFi control without purchasing a separate module
• You are looking for a condensing model for maximum efficiency

Verdict: Rinnai RE180iP 8.5 GPM Propane is a high-capacity indoor heater for homes needing hot water for seven fixtures. It suits buyers who value durability and compact size over built-in smart features.

7 Best 199,000 btu

MIZUDO 10.3 GPM Propane Tankless Heater

Best for: large households with high hot water demands

Fuel Type

Propane

Flow Rate

10.3 GPM

BTU

199,000 BTU

Installation Location

Indoor

Voltage

120V

Temperature Control

95-149°F, ±1°F

View on Amazon: MIZUDO 10.3 GPM Propane Tankless Heater

This MIZUDO propane tankless water heater delivers 199,000 BTU of heating input for up to 10.3 GPM. It supports simultaneous hot water use across multiple bathrooms and appliances. The unit features ±1°F precise temperature control, adjustable up to 149°F. It includes smart WiFi control and Alexa compatibility. With CSA certification for indoor installation, it suits busy households needing high-volume hot water.

Pros

• 199,000 BTU input supports up to 10.3 GPM flow rate
• ±1°F precise temperature control with adjustable range up to 149°F
• Smart WiFi control with Amazon Alexa compatibility
• 0.53 GPM low-flow activation for efficiency
• Sealed concentric direct-vent system prevents backdraft

Cons

• Not recommended for elevations above 3,000 feet
• Requires professional installation for proper venting
• Limited to indoor use only

Good fit if

• You need high flow rates for multiple bathrooms
• You want smart app control for temperature management
• You have indoor space for a direct-vent unit

Skip if

• You live above 3,000 feet elevation
• You require outdoor installation
• You prefer natural gas over propane

Verdict: MIZUDO 199,000 BTU Propane Tankless Heater is ideal for large households with high hot water demands who value smart connectivity and precise temperature control.

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