Thermomate Tankless Water Heater Electric or Thermomate Propane Tankless Water Heater? Which Thermomate Model to Buy
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Choosing between a thermomate tankless water heater electric vs propane tankless water model depends on your home’s infrastructure. Both units provide on-demand hot water and fit indoor spaces. The electric option delivers higher flow rates at 18kW, while the propane model offers precise temperature stability with 75,000 BTU. You must decide based on available power, gas lines, and your specific hot water demands.
Key differences
| Aspect | Thermomate 18kW Electric Tankless Water Heater | Thermomate 75,000 BTU Indoor Propane Water Heater |
|---|---|---|
| Fuel Type | Electric | Propane |
| Power/BTU | 18kW | 75,000 BTU/hr |
| Max Flow Rate | Up to 4.4 GPM | Up to 3.06 GPM |
| Voltage | 208-240V | Not listed |
| Dimensions | 17.1" H x 13.1" W x 3.1" D | 21" H x 13" W x 7" D |
| Temp Control Precision | 1° increment | ±1°F stability |
Which one should you choose?
Choose Thermomate 18kW Electric Tankless Water Heater if
- You have a 240V electrical panel with space for two 40-amp breakers.
- You need higher flow rates for multiple fixtures or larger showers.
- You prefer a thinner unit that fits into tighter wall spaces.
Choose Thermomate 75,000 BTU Indoor Propane Water Heater if
- You have a propane gas line and proper venting available.
- You want precise temperature stability within ±1°F during use.
- You need built-in frost protection for colder environments.
Verdict: Choose the electric model if your electrical system supports high amperage and you prioritize maximum flow rate. Select the propane model if you have gas infrastructure and value tight temperature stability. Your decision rests on existing home utilities rather than performance superiority.
Thermomate Electric vs Propane Specs
fuel type
The Thermomate 18kW Electric Tankless Water Heater relies on 240V electricity to heat water. It requires a dedicated 80Amp breaker setup using two double-pole 40AMP breakers and 8AWG wire. This model is strictly electric. In contrast, the Thermomate 75,000 BTU Indoor Propane Water Heater uses propane gas. It features a 1/2" NPT gas inlet and a 3" OD vent for exhaust. The propane unit also includes a UL-approved 120V plug for its control electronics, but the heating source is gas. Your choice depends on whether you have the necessary electrical panel capacity or existing gas lines.
flow rate
Flow rate determines how much hot water you can use at once. The Thermomate 18kW Electric Tankless Water Heater provides up to 4.4 gallons per minute. This higher flow supports multiple fixtures or a very strong shower. The Thermomate 75,000 BTU Indoor Propane Water Heater delivers up to 3.06 GPM. It reliably provides a comfortable single shower at 2 GPM when inlet water is 52°F. In warmer months with 65°F inlet water, it maintains full shower performance and can supply an additional faucet at 0.5 GPM. If you need higher volume for multiple simultaneous uses, the electric model has the advantage.
temperature control
Precision in water temperature affects comfort. The Thermomate 18kW Electric Tankless Water Heater allows you to adjust the output in 1°F increments. You can set the digital display anywhere from 80°F to 140°F. The unit auto-adjusts energy consumption based on incoming water temperature to maintain stability. The Thermomate 75,000 BTU Indoor Propane Water Heater uses advanced sensors to adjust heating output 20,000 times per second. It maintains temperature stability within ±1°F. Both models offer precise control, but the propane unit’s rapid adjustment cycle may handle fluctuating inlet temperatures more dynamically.
efficiency
Efficiency impacts your long-term operating costs. The Thermomate 18kW Electric Tankless Water Heater uses self-modulating technology to regulate energy use. It claims 99.8% efficiency and can save up to 60% on water heating costs compared to traditional tank heaters. The heating element is separated from the water tube to reduce scale and corrosion. The Thermomate 75,000 BTU Indoor Propane Water Heater has a thermal efficiency of 98% with a UEF of 0.81. It features an oxygen-free copper heat exchanger for better heat transfer. The propane model states it can lower annual operating costs by approximately 30% compared to traditional water heaters.
dimensions
Space is often a constraint for tankless installations. The Thermomate 18kW Electric Tankless Water Heater is compact, measuring 17.12 inches high, 13.12 inches wide, and 3.12 inches deep. Its slim profile fits into tight spaces easily. The Thermomate 75,000 BTU Indoor Propane Water Heater is taller and deeper. It measures 21 inches high, 13 inches wide, and 7 inches deep. While both are wall-mounted and save floor space compared to tank models, the electric unit is significantly thinner. If you have a narrow installation spot, the electric model fits better.
safety features
Both units include multiple safety protections. The Thermomate 18kW Electric Tankless Water Heater is ETL certified. It features overheating protection and auto-stops heating if no water is detected. It also includes leakage protection. The Thermomate 75,000 BTU Indoor Propane Water Heater integrates eight specific protections: boil-dry, freeze, flame-out, overheating, over-temperature, pipe blockage, high-temperature lock, and excessive air pressure. It also has auto-activating frost protection when temperatures hit 41°F. The propane model lists a more comprehensive set of specific gas-related safety mechanisms.
Which Thermomate Model Fits Your Needs
You have 240V wiring and need high flow
Choose the electric model if your home already has the required 80Amp breaker setup with two double-pole 40AMP breakers. It delivers up to 4.4 GPM, making it suitable for multiple fixtures. The 18kW output ensures robust performance for larger households with higher hot water demands.
You want precise temperature stability without complex wiring
Select the propane unit for superior temperature control. It maintains stability within ±1°F by adjusting gas input 20,000 times per second. This precision prevents cold water shocks. It also includes eight safety protections and frost prevention, offering reliability without the need for heavy electrical infrastructure.
You need easy installation with standard plumbing
The propane model simplifies installation with standard 3/4" NPT water connections and a 1/2" NPT gas inlet. It uses a UL-approved 120V plug for power, avoiding the need for dedicated high-amperage circuits. This makes it a practical choice for retrofitting or homes without suitable electrical panels.
The products compared
Thermomate 18kW Electric Tankless Water Heater
Best for: Whole-house electric hot water with high flow
- 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 electric unit delivers up to 4.4 GPM of hot water at 18kW. It features a compact 17.12 x 13.12 x 3.12 inch design that mounts easily on walls. The digital display allows precise temperature control from 80°F to 140°F in 1° increments. You get instant heat with self-modulating technology that adjusts energy use based on incoming water temperature. It requires two 40-amp double-pole breakers and 8AWG wiring for proper installation.
Pros
- High flow rate of up to 4.4 GPM for multiple fixtures
- Precise digital temperature control with 1° increments
- Self-modulating technology ensures energy efficiency
- Compact wall-mount design saves floor space
Cons
- Requires two 40-amp double-pole breakers and heavy gauge wiring
- Indoor installation only due to electrical safety standards
- No remote control or smart app connectivity mentioned
Good fit if
- You need high flow for a whole-house setup
- You have the electrical capacity for dual 40-amp breakers
- You want precise temperature adjustments in 1° increments
Skip if
- You are installing outdoors without weatherproofing
- Your electrical panel cannot support two 40-amp breakers
- You prefer propane over electric heating sources
Verdict: Thermomate 18kW Electric Tankless Water Heater fits homes with strong electrical panels needing high flow. It suits those who want precise temperature control and space-saving wall mounting. The unit requires specific wiring and breakers for safe operation.
Thermomate 75,000 BTU Indoor Propane Water Heater
Best for: Indoor single-shower propane setups
- Fuel Type
- Propane
- Flow Rate
- Up to 3.06 GPM
- BTU
- 75,000 BTU
- Installation Location
- Indoor
- Voltage
- 120V
- Temperature Control
- ±1°F
View on Amazon: Thermomate 75,000 BTU Indoor Propane Water Heater Affiliate link
This Thermomate propane unit delivers up to 3.06 GPM at 75,000 BTU. It fits indoor spaces with dimensions of 21.7 inches high and 13.8 inches wide. The system maintains temperature within ±1°F using advanced sensors. It includes eight safety protections and frost prevention. You get reliable hot water for a single shower or kitchen sink without the bulk of a tank.
Pros
- 75,000 BTU/hr heating capacity
- Temperature stability within ±1°F
- Eight integrated safety protections
- Compact 21.7" H x 13.8" W footprint
- 98% thermal efficiency
Cons
- Indoor installation only
- Lower flow rate than electric alternative
- Requires propane fuel supply
Good fit if
- You need a compact indoor unit
- You have access to propane gas
- You want precise temperature control
Skip if
- You require outdoor installation
- You need high flow for multiple showers
- You only have electrical power
Verdict: Thermomate 75,000 BTU Propane Indoor Heater suits users with propane access who need a space-saving indoor solution. It provides stable heat for single-point use but lacks the volume for whole-house simultaneous demand.
Specifications side by side
| Spec | Thermomate 18kW Electric Tankless Water Heater | Thermomate 75,000 BTU Indoor Propane Water Heater |
|---|---|---|
| Fuel Type | Electric | Propane |
| Flow Rate | Up to 4.4GMP | Up to 3.06 GPM |
| BTU | not stated | 75,000 BTU |
| Wattage | 18kW | not stated |
| Installation Location | Indoor | Indoor |
| Voltage | 240V | 120V |
| Temperature Control | 80°F to 140°F, ±1°F | ±1°F |
| Certification | ETL | not stated |
| Dimensions | 17.12" x 13.12" x 3.12" | 21"H × 13"W × 7"D |
| Weight | not stated | 19.8 pounds |
| Size | 240V/18kW | not stated |
| Color | Gray | Bright Silver |
| Model | ET180 | CZ264LP |
Frequently asked questions
Can I install the Thermomate propane heater in my basement?
Yes, the Thermomate 75,000 BTU Indoor Propane Water Heater is designed for indoor installation. It fits well in basements or utility rooms where ventilation is available. The unit measures 13.8 inches wide and 21.7 inches tall. You must ensure the space meets indoor safety standards for propane appliances. It is not rated for outdoor use.
What size breaker do I need for the 18kW electric model?
You need a dedicated 80Amp breaker setup for the Thermomate 18kW Electric Tankless Water Heater. This requires two double-pole 40AMP breakers. You must also use 8AWG wire for safe operation. The unit draws significant power, so your electrical panel must support this load. Check your home’s wiring capacity before installing.
Which model is better for a whole house?
The Thermomate 18kW Electric Tankless Water Heater is better for whole-house use. It provides higher flow rates suitable for multiple fixtures. The propane model is limited to single-shower setups. It lacks the volume for simultaneous whole-house demand. Choose the electric unit if you need consistent hot water for showers, sinks, and appliances.
How big is the Thermomate propane water heater?
The Thermomate 75,000 BTU Indoor Propane Water Heater is compact. It measures 13.8 inches in width and length, with a height of 21.7 inches. It weighs 19.8 pounds. The bright silver finish fits standard indoor spaces. Its small footprint allows for easy wall mounting in tight areas like closets or utility rooms.
Does the electric heater require gas lines?
No, the Thermomate 18kW Electric Tankless Water Heater does not use gas. It runs entirely on 240V electricity. You need proper electrical wiring and breakers instead of gas lines. This makes it ideal for homes without natural gas or propane access. It provides on-demand hot water using only electrical power.
Can I use the propane heater for outdoor showers?
No, the Thermomate 75,000 BTU Indoor Propane Water Heater is strictly for indoor use. It is not designed for outdoor environments. Exposure to weather could damage the unit and create safety hazards. If you need an outdoor solution, look for a model specifically rated for outdoor installation. This unit requires an indoor, ventilated space.