Thermomate Tankless Water Heater Electric vs Thermomate 98: Spec Comparison
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This thermomate tankless water heater electric vs 98 comparison helps you choose the right unit for your home. Both ThermoMate models provide instant hot water and fit indoor spaces. The main difference is the fuel source. One uses 18kW of electricity, while the other runs on propane. Each system offers distinct flow rates and temperature controls. You need to match the power source to your home’s infrastructure. Read on to see how their specs compare side by side.
Key differences
| Aspect | Thermomate 18kW Electric Tankless Water Heater | ThermoMate 4 GPM Propane Tankless Water Heater |
|---|---|---|
| Fuel Type | Electric | Propane |
| Power Input | 18kW | 98,500 BTU/hr |
| Flow Rate | Up to 4.4 GPM | Up to 4 GPM |
| Voltage | 208~240 Volt | 120V (for control) |
| Dimensions | 17.12" x 13.12" x 3.12" | 21" H x 13" W x 7" D |
| Certification | ETL | CSA |
Which one should you choose?
Choose Thermomate 18kW Electric Tankless Water Heater if
- You have a dedicated 240V electrical circuit with an 80A breaker.
- You need the highest possible flow rate for multiple fixtures.
- You prefer a thinner unit that fits into tighter wall spaces.
Choose ThermoMate 4 GPM Propane Tankless Water Heater if
- You have access to a propane tank and gas lines.
- You want precise temperature stability within ±1°F.
- You need built-in freeze protection for cold climates.
Verdict: Choose the electric model if your home has ample electrical capacity and you prioritize a higher flow rate. Select the propane model if you have gas infrastructure and want advanced temperature stability with freeze protection. Both units deliver instant hot water for indoor residential use.
Electric vs Propane Spec Breakdown
Fuel type and power
Thermomate 18kW Electric Tankless Water Heater relies on 18kW of electrical power at 208 to 240 volts. It requires two double-pole 40-amp breakers and 8AWG wire. This model draws up to 76 amps at peak load. ThermoMate 4 GPM Propane Tankless Water Heater uses propane gas with a 98,500 BTU/hr input. It connects to a standard 1/2" NPT gas line and uses a UL-approved 120V plug for controls only. You must choose between high electrical demand or gas infrastructure. The electric unit needs dedicated heavy-duty circuitry, while the propane unit needs a gas line and proper venting.
Flow rate capacity
Thermomate 18kW Electric Tankless Water Heater delivers up to 4.4 GPM. This higher flow supports multiple fixtures or a strong shower pressure. ThermoMate 4 GPM Propane Tankless Water Heater provides up to 4 GPM. It handles one shower and one faucet simultaneously at a 43°F rise. The electric model offers a slight edge in maximum volume. If you need higher flow for larger showers or multiple simultaneous uses, the 4.4 GPM rating matters. The propane model is sufficient for standard household use but caps slightly lower.
Temperature precision
ThermoMate 4 GPM Propane Tankless Water Heater adjusts heating output 20,000 times per second. It maintains temperature stability within ±1°F using advanced sensors. This precision prevents sudden temperature fluctuations. Thermomate 18kW Electric Tankless Water Heater allows adjustments in 1°F increments from 80°F to 140°F. It uses self-modulating technology based on inlet temperature. While the electric unit offers wide range control, the propane model provides faster electronic response. The ±1°F stability is a technical advantage for comfort.
Physical dimensions
Thermomate 18kW Electric Tankless Water Heater measures 17.12" H x 13.12" W x 3.12" D. Its slim 3.12-inch depth fits well in tight spaces like closets or under sinks. ThermoMate 4 GPM Propane Tankless Water Heater measures 21" H x 13" W x 7" D. It is taller and deeper due to the gas combustion chamber. The electric model is significantly thinner. If wall space or clearance is limited, the electric unit’s compact profile is easier to install. The propane unit requires more depth for venting and service access.
Safety certifications
Thermomate 18kW Electric Tankless Water Heater is ETL certified. It includes overheating protection and auto-stop heating when no water flow is detected. ThermoMate 4 GPM Propane Tankless Water Heater is CSA certified. It features boil-dry, freeze, flame-out, overheat, and high-temperature lock protections. It also includes freeze protection activating at 41°F. Both meet safety standards for indoor use. The propane model lists more specific failure-mode protections. The electric model focuses on electrical safety and flow detection. Both are reliable for residential installation.
Which unit fits your home best
Homeowners with existing electrical capacity
This electric model delivers up to 4.4 GPM at 18kW. It requires two 40-amp breakers and 8AWG wire. The digital display lets you adjust temperature in 1° increments from 80°F to 140°F. Its compact 17-inch height fits tight spaces. Choose this if you have the necessary electrical infrastructure for high-power heating.
Users in colder climates needing stability
This propane unit features a control chip that adjusts heating 20,000 times per second. It maintains temperature stability within ±1°F. The built-in freeze protection activates at 41°F. It supports a single shower even with inlet temperatures as low as 40°F. Select this for consistent performance in cold weather conditions.
Those wanting easy diagnostic troubleshooting
This model includes a 3.5-inch LED display showing flow, fan, and flame status. It provides advanced error codes for fast troubleshooting. The UL-certified 120V cord allows easy monitoring. You can adjust water temperature from 90°F to 140°F directly on the unit. This feature set simplifies maintenance and system checks.
The products compared
Thermomate 18kW Electric Tankless Water Heater
Best for: High-flow indoor electric hot water needs
- Fuel Type
- Electric
- Flow Rate
- Up to 4.4GMP
- Wattage
- 18kW
- Installation Location
- Indoor
- Voltage
- 240V
- Temperature Control
- 80°F to 140°F, ±1°F
View on Amazon: Thermomate 18kW Electric Tankless Water Heater Affiliate link
This Thermomate unit delivers up to 4.4 GPM of hot water at 18kW. It features a compact 17.12 by 13.12 by 3.12-inch design for wall mounting. The digital display allows precise temperature adjustments in 1-degree increments from 80°F to 140°F. It requires a 240V circuit with two 40-amp breakers. This electric heater suits homes needing steady flow without a storage tank.
Pros
- High flow rate of up to 4.4 GPM
- Precise digital temperature control in 1-degree increments
- Compact wall-mounted design saves floor space
- ETL certified for safety and overheating protection
Cons
- Requires substantial electrical infrastructure with 80-amp capacity
- Indoor installation only, not suitable for outdoors
- Lacks remote control or smart app connectivity
Good fit if
- You have a dedicated 240V circuit with double-pole 40-amp breakers
- You need a high-flow unit for multiple simultaneous uses
- You want precise temperature adjustments in small increments
Skip if
- You only have a standard 120V household outlet
- You need an outdoor-rated unit for exterior walls
- You prefer a simpler analog dial interface
Verdict: Thermomate 18kW Electric Tankless Water Heater is a high-output solution for homes with adequate electrical capacity. It fits users who prioritize flow rate and precise temperature settings over smart features.
ThermoMate 4 GPM Propane Tankless Water Heater
Best for: single shower and one faucet use
- 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 Affiliate link
The Thermomate 98,500 BTU propane tankless water heater delivers up to 4 GPM for one shower and one faucet. It features a copper heat exchanger with 98% thermal efficiency and precise temperature control within ±1°F. This indoor unit measures 21.7 inches high and includes safety protections like freeze and boil-dry safeguards. It suits households needing reliable hot water with smart diagnostics.
Pros
- High 98% thermal efficiency with a 0.81 UEF rating
- Precise temperature stability within ±1°F using advanced sensors
- Compact indoor design measuring 21.7" H x 13.8" W
- Comprehensive safety features including freeze protection at 41°F
- Smart LED display shows flow, fan, and flame status
Cons
- Indoor installation only, not suitable for outdoor use
- Requires 3-inch OD venting for proper exhaust
- Propane fuel type limits placement near gas lines
Good fit if
- You need hot water for one shower and one faucet simultaneously
- You have access to propane gas and indoor venting space
- You want precise temperature control within ±1°F
Skip if
- You require outdoor installation capabilities
- You need multiple showers running at full flow
- You prefer natural gas over propane fuel
Verdict: Thermomate 98,500 BTU Propane Tankless Water Heater fits households needing reliable hot water for one shower and one faucet with precise temperature control. Its compact indoor design and high efficiency make it ideal for spaces with propane access.
Specifications side by side
| Spec | Thermomate 18kW Electric Tankless Water Heater | ThermoMate 4 GPM Propane Tankless Water Heater |
|---|---|---|
| Fuel Type | Electric | Propane |
| Flow Rate | Up to 4.4GMP | Up to 4 GPM |
| BTU | not stated | 98,500 BTU |
| Wattage | 18kW | not stated |
| Installation Location | Indoor | Indoor |
| Voltage | 240V | 120V |
| Temperature Control | 80°F to 140°F, ±1°F | 90–140°F, ±1°F |
| Certification | ETL | CSA |
| Dimensions | 17.12" x 13.12" x 3.12" | 21 x 13 x 7 in |
| Weight | not stated | 21.2 pounds |
| Size | 240V/18kW | not stated |
| Color | Gray | Metallic Silver |
| Model | ET180 | CZ360LP |
Frequently asked questions
Can the Thermomate 18kW electric heater run on a standard 120V outlet?
No. The Thermomate 18kW model requires a 240V power supply. It needs two double-pole 40-amp breakers and 8AWG wiring to operate safely. You cannot plug this unit into a standard household outlet. Proper electrical infrastructure is mandatory for this high-output electric tankless heater.
What is the physical size difference between the electric and propane models?
The electric unit measures 13.1 by 17.1 by 13.1 inches. The propane Thermomate 98 is slightly taller and wider at 13.8 by 21.7 by 13.8 inches. The propane unit also weighs 21.2 pounds. Both fit indoor spaces but have different footprints and heights.
Which unit is better for a single shower and one faucet?
The Thermomate 98 Propane model is designed for single shower and one faucet use. It delivers reliable hot water with precise temperature control. Its compact indoor design and high efficiency make it ideal for households with propane access who do not need high simultaneous flow.
Does the electric model have a digital display?
Yes. The Thermomate 18kW Electric Tankless Water Heater includes a digital display. It allows you to adjust the water temperature in 1° increments. The range spans from 80°F to 140°F, giving you precise control over your hot water output settings.
Is the Thermomate 98 suitable for outdoor installation?
No. The Thermomate 98 Propane Tankless Water Heater is rated for indoor installation only. Its design and specifications are intended for interior spaces. You must install this unit inside your home where propane access is available and ventilation requirements are met.
What fuel types do these two Thermomate heaters use?
The first unit uses electricity, specifically 18kW of power at 240V. The second unit, the Thermomate 98, uses propane. These are the only two fuel options covered in this comparison. Your choice depends on your home’s available energy source and infrastructure.