The Best Thermomate Tankless Water Heaters in 2026: 8 Picks
As an Amazon Associate we earn from qualifying purchases. Links on this page are affiliate links.
We evaluated 8 models to identify the best thermomate tankless water heaters for your home. Thermomate offers a diverse range including compact electric mini-tanks, high-capacity electric units, and propane or natural gas heaters. The Thermomate 6.5-Gallon Under-Sink Electric Mini-Tank leads this list because it provides simple 120-volt point-of-use heating with flexible mounting options. Our selection process relied strictly on the specifications published on the product listings. We compared voltage, capacity, dimensions, and fuel types to ensure each pick matches your specific installation needs.
Quick picks
Our 8 picks
Thermomate 6.5-Gallon Under-Sink Electric Mini-Tank
Best for: point-of-use under-sink installations on standard 120V power
- Fuel Type
- Electric
- Wattage
- 1.44 kW
- Capacity
- 6.5 Gallons
- Voltage
- 120V
- Temperature Control
- 50°F to 149°F
- Certification
- UL Listed
View on Amazon: Thermomate 6.5-Gallon Under-Sink Electric Mini-Tank
This Thermomate 6.5-gallon electric mini-tank water heater delivers dedicated point-of-use hot water directly under your sink or counter. It runs on a standard 120-volt outlet with a 1.44 kW draw, pulling 12 amps through its included two-foot power cord. The thermostat provides three temperature levels from 50°F to 149°F alongside a freeze-prevention setting. It suits you if you need reliable point-of-use storage without installing dedicated 240-volt electrical wiring.
Pros
- Plugs into a standard 120V outlet drawing 12 amps
- Offers 3 temperature settings from 50°F to 149°F plus freeze protection
- Includes a temperature and pressure relief valve
- Supports both wall and floor mounting
Cons
- Short 2-foot power cord requires an outlet close to the unit
- Limited to 6.5 gallons of stored hot water before requiring recovery
Good fit if
- You need a dedicated point-of-use supply for an under-sink installation.
- You have an accessible 120-volt outlet within two feet of the heater.
- You want basic temperature adjustment with built-in freeze protection.
Skip if
- You require continuous whole-home hot water rather than point-of-use capacity.
- You lack clearance under your counter for a 17.7-inch by 17.7-inch tank.
Verdict: Thermomate 6.5-Gallon Mini-Tank Water Heater delivers simple 120-volt point-of-use heating with flexible floor or wall mounting. It provides 6.5 gallons of dedicated hot water without requiring high-voltage wiring upgrades.
Thermomate 18kW Electric Tankless Water Heater
Best for: homes with 80-amp electrical capacity
- Fuel Type
- Electric
- Wattage
- 18kW
- Voltage
- 240 Volt
- Temperature Control
- 80°F to 140°F, 1° increment
- Certification
- ETL Certified
- Dimensions
- 17.12" x 13.12" x 3.12"
View on Amazon: Thermomate 18kW Electric Tankless Water Heater
This Thermomate 18kW electric tankless water heater delivers up to 4.4 GPM on demand using a 240-volt electrical supply. It features an adjustable digital thermostat ranging from 80°F to 140°F in 1-degree increments, along with self-modulating power output. Measuring 17.12 by 13.12 by 3.12 inches, it mounts directly to your wall. This model suits you if you need steady, multi-fixture indoor hot water without maintaining a bulky storage tank.
Pros
- Flow rate up to 4.4 GPM on demand
- Digital temperature adjustment from 80°F to 140°F in 1° increments
- Heating element separated from water tube to minimize mineral buildup
- ETL certified with overheating and dry-fire protection
Cons
- Requires two 40-amp double-pole breakers and 8 AWG wiring
- Rated for indoor installation only
Good fit if
- You have an electrical panel that supports an 80-amp breaker setup.
- You need up to 4.4 GPM of continuous hot water for indoor fixtures.
- You want single-degree digital temperature adjustments.
Skip if
- You do not have enough panel capacity for two double-pole 40A breakers.
- You need an outdoor-rated water heater.
- You prefer gas fuel over a 240-volt electric connection.
Verdict: Thermomate 18kW Electric Tankless Water Heater delivers 4.4 GPM on demand with precise digital controls for homes with sufficient 80-amp electrical service.
Thermomate 2.5-Gallon Under-Sink Mini-Tank Heater
Best for: single-sink point-of-use installations and booster setups
- Fuel Type
- Electric
- Capacity
- 2.5 Gallons
- Voltage
- 120V
- Temperature Control
- 68℉-140℉
- Use
- Under Sink
- Dimensions
- 13.6 × 13.2 × 18.9 inches
View on Amazon: Thermomate 2.5-Gallon Under-Sink Mini-Tank Heater
This 2.5-gallon electric mini-tank heater delivers dedicated hot water directly at your sink. It runs on a standard 120V outlet using an included power cord and connects via 1/2-inch NPT fittings. An adjustable dial lets you set temperatures between 68°F and 140°F. It suits you if you need a compact point-of-use unit or an inline booster to reduce wait times at an isolated kitchen or bathroom faucet.
Pros
- Plugs directly into a standard 120V outlet with included cord
- Adjustable temperature range from 68°F to 140°F
- Includes temperature and pressure relief valve
- Supports shelf, wall, or floor mounting
Cons
- Small 2.5-gallon capacity depletes during continuous running water
- Requires physical cabinet or floor footprint unlike tankless designs
Good fit if
- You need a dedicated hot water supply for a single sink.
- You have a standard 120V outlet accessible near your fixture.
- You want an inline booster to reduce delivery lag from a primary heater.
Skip if
- You need endless continuous hot water for showers or high-demand fixtures.
- You prefer a true tankless unit without storage volume under your cabinet.
Verdict: Thermomate 2.5 Gallon Electric Mini Tank Water Heater provides dedicated point-of-use heating with simple 120V plug-in installation. It is an effective compact choice for single-sink setups or inline boosting.
Thermomate 6kW Electric Tankless Water Heater
Best for: single-sink point-of-use handwashing applications
- Fuel Type
- Electric
- Flow Rate
- 1.07 GPM
- Wattage
- 6 kW
- Voltage
- 240 V
- Temperature Control
- 85°F–131°F, 1° increment
- Certification
- ETL
View on Amazon: Thermomate 6kW Electric Tankless Water Heater
The Thermomate 6kW Electric Tankless Water Heater delivers on-demand hot water for dedicated single-sink setups. Running on 240 volts with a 6kW output, it provides a 1.0 GPM flow rate at a 35°F temperature rise. Measuring 10.96 by 7.4 by 2.52 inches, this compact unit fits inside tight cabinet spaces beneath bathroom or utility sinks when you need point-of-use heating without a storage tank.
Pros
- Delivers 1.0 GPM at a 35°F temperature rise for point-of-use sink setups
- Digital touch control adjusts temperature from 85°F to 131°F in 1° increments
- Compact 10.96 x 7.4 x 2.52-inch footprint fits under standard sink cabinets
- Cast aluminum heating element separated from the SUS 304 stainless steel water tube
Cons
- Requires hardwired 240V power with a 30A breaker rather than a standard 120V plug
- Flow rate of 1.0 GPM limits use to a single handwashing faucet rather than whole-home demand
Good fit if
- You need a dedicated under-sink water heater delivering up to 1.0 GPM.
- You have a 240V electrical connection with a 30A breaker and 10 AWG wiring.
- You want digital temperature adjustments in 1° increments from 85°F to 131°F.
Skip if
- You need whole-home hot water or simultaneous multi-fixture capacity.
- You only have access to a standard 120V outlet at the installation site.
Verdict: Thermomate 6kW Electric Tankless Water Heater is a compact point-of-use solution engineered specifically for single-sink installations requiring 240-volt power. It delivers steady handwashing temperatures without taking up valuable cabinet storage.
ThermoMate 4 GPM Propane Tankless Water Heater
Best for: Small households using indoor propane hookups
- 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
This indoor propane tankless water heater supplies up to 4 GPM with a 98,500 BTU output. It runs on liquid propane and requires a 3-inch vent plus a standard 120-volt electrical outlet. You can adjust water output temperatures from 90°F to 140°F on its LED screen. It suits small to medium households that need enough hot water to run one shower and a sink simultaneously.
Pros
- Up to 4 GPM flow rate powered by 98,500 BTU
- Delivers water temperatures between 90°F and 140°F with ±1°F stability
- Includes a 3.5-inch LED diagnostic display with error codes
- Built-in freeze protection activates automatically at 41°F
Cons
- Requires a dedicated 3-inch OD vent line for indoor exhaust
- Needs an active 120V electrical outlet connection to operate
Good fit if
- You use liquid propane as your primary fuel source.
- You need to supply hot water to a shower and a faucet at the same time.
- You want an indoor unit with digital temperature adjustment up to 140°F.
Skip if
- You need a natural gas water heater instead of liquid propane.
- You require more than 4 GPM of hot water output for multiple simultaneous showers.
Verdict: Thermomate 4 GPM Indoor Propane Tankless Heater delivers reliable indoor hot water for low-to-medium demand homes using liquid propane. Its 98,500 BTU rating and stable temperature sensors make it a dependable choice for running a shower and faucet together.
Thermomate 75,000 BTU Indoor Propane Water Heater
Best for: single-shower propane indoor water heating
- Fuel Type
- Propane
- Flow Rate
- Up to 3.06 GPM
- BTU
- 75,000 BTU/hr
- Installation Location
- Indoor
- Temperature Control
- ±1°F
- Dimensions
- 21" H x 13" W x 7" D
View on Amazon: Thermomate 75,000 BTU Indoor Propane Water Heater
This indoor tankless water heater runs on propane, delivering up to 75,000 BTU and a maximum flow rate of 3.06 GPM. You get precise heating within ±1°F, standard 3/4-inch NPT water connections, and built-in freeze protection down to 41°F. It suits you if you need a dedicated single-shower setup running off liquid propane in a compact indoor footprint.
Pros
- Delivers up to 3.06 GPM with a 75,000 BTU heating capacity
- Temperature sensors maintain output stability within ±1°F
- Automatic frost protection activates via ceramic heating cores at 41°F
- Oxygen-free copper heat exchanger provides a 0.81 UEF rating
Cons
- Requires dedicated indoor venting via a 3-inch OD vent
- Caps at 3.06 GPM, limiting simultaneous multi-fixture use
- Requires a 120V power outlet alongside the propane line
Good fit if
- You need a propane-powered indoor water heater sized for single-shower demands.
- You want automatic freeze protection for spaces that reach 41°F.
- You have space for a 3-inch OD vent and 3/4-inch NPT plumbing lines.
Skip if
- You need high flow rates across multiple simultaneous hot water fixtures.
- You use natural gas rather than liquid propane.
- You lack a nearby 120V electrical outlet for the power plug.
Verdict: Thermomate 75,000 BTU Indoor Propane Water Heater delivers steady single-fixture hot water with tight ±1°F temperature control. Its compact indoor dimensions and automated frost safeguards make it a reliable choice for dedicated propane setups.
Thermomate 11kW Electric Tankless Water Heater
Best for: single-fixture sinks and low-flow bathrooms
- Fuel Type
- Electric
- Flow Rate
- Up to 2.6GPM
- Wattage
- 11kW
- Voltage
- 208~240 Volt
- Temperature Control
- Within 1°F
- Certification
- ETL Certified
View on Amazon: Thermomate 11kW Electric Tankless Water Heater
The Thermomate 11kW Electric Tankless Water Heater runs on 208 to 240 volts and delivers 2.15 GPM at a 35°F temperature rise. It uses self-modulating power to maintain temperatures within 1°F of your setting. Measuring 11.8 by 14.8 by 3.13 inches, it fits tight spaces near fixtures. You will find it suitable for a single bathroom, office break room, or low-flow point-of-use sink setup.
Pros
- Delivers up to 2.15 GPM at a 35°F temperature rise
- Self-modulating heating keeps water within 1°F of setting
- Heating element is separated from water tube to reduce scale
- Compact wall-mounted profile measuring 11.8 by 14.8 by 3.13 inches
Cons
- Requires two separate double-pole 30-amp breakers
- Flow rate of 2.15 GPM limits use to low-flow or single fixtures
Good fit if
- You need on-demand hot water for a single bathroom or break room sink.
- You have electrical capacity for two double-pole 30-amp breakers.
Skip if
- You need whole-house capacity to run multiple high-flow fixtures at once.
- Your electrical panel cannot support a 46-amp maximum draw.
Verdict: Thermomate 11kW Electric Tankless Water Heater delivers steady 2.15 GPM output for single-point setups requiring precise 1°F temperature control.
Thermomate 98,500 BTU Natural Gas Tankless Water Heater
Best for: small households with natural gas hookups
- Fuel Type
- Natural Gas
- Flow Rate
- Up to 4 GPM
- BTU
- 98,500 BTU/hr
- Installation Location
- Indoor
- Certification
- CSA (Certificate No. 80296889)
- Dimensions
- 21" H x 13" W x 7" D
View on Amazon: Thermomate 98,500 BTU Natural Gas Tankless Water Heater
This indoor natural gas tankless water heater delivers up to 4 GPM using a 98,500 BTU burner. With a 0.81 UEF rating and an oxygen-free copper heat exchanger, it handles a 43°F temperature rise for a shower and faucet simultaneously. If your home has a natural gas line and requires an indoor unit capable of running one or two fixtures at a time, this model fits your space.
Pros
- Maximum flow rate of 4 GPM with 98,500 BTU/hr natural gas burner
- Oxygen-free copper heat exchanger with 0.81 UEF rating
- Water and gas sensors maintain temperature within 1°F
- Standard 3/4-inch NPT water and 1/2-inch NPT gas connections
Cons
- Requires a 3-inch OD vent through an indoor exterior wall or roof
- Limited to a single shower when incoming water drops to 40°F
- Requires a 120V electrical outlet for operation
Good fit if
- You have a natural gas supply line and need an indoor water heater.
- You run one shower and one sink simultaneously in moderate incoming water conditions.
Skip if
- You rely on liquid propane instead of natural gas.
- You need to supply multiple high-flow showers at the same time in freezing weather.
Verdict: Thermomate 98,500 BTU Natural Gas Tankless Water Heater provides steady on-demand hot water for up to two fixtures using natural gas and standard 120V power. It is a solid indoor option for households with access to natural gas infrastructure.
Specifications side by side
| Spec | Thermomate 6.5-Gallon Under-Sink Electric Mini-Tank | Thermomate 18kW Electric Tankless Water Heater | Thermomate 2.5-Gallon Under-Sink Mini-Tank Heater | Thermomate 6kW Electric Tankless Water Heater | ThermoMate 4 GPM Propane Tankless Water Heater | Thermomate 75,000 BTU Indoor Propane Water Heater | Thermomate 11kW Electric Tankless Water Heater | Thermomate 98,500 BTU Natural Gas Tankless Water Heater |
|---|---|---|---|---|---|---|---|---|
| Fuel Type | Electric | Electric | Electric | Electric | Propane | Propane | Electric | Natural Gas |
| Flow Rate | not specified | not specified | not specified | 1.07 GPM | Up to 4 GPM | Up to 3.06 GPM | Up to 2.6GPM | Up to 4 GPM |
| BTU | not specified | not specified | not specified | not specified | 98,500 BTU | 75,000 BTU/hr | not specified | 98,500 BTU/hr |
| Wattage | 1.44 kW | 18kW | not specified | 6 kW | not specified | not specified | 11kW | not specified |
| Installation Location | not specified | not specified | not specified | not specified | Indoor | Indoor | not specified | Indoor |
| Capacity | 6.5 Gallons | not specified | 2.5 Gallons | not specified | not specified | not specified | not specified | not specified |
| Voltage | 120V | 240 Volt | 120V | 240 V | 120V | not specified | 208~240 Volt | not specified |
| Temperature Control | 50°F to 149°F | 80°F to 140°F, 1° increment | 68℉-140℉ | 85°F–131°F, 1° increment | 90–140°F, ±1°F | ±1°F | Within 1°F | not specified |
| Certification | UL Listed | ETL Certified | not specified | ETL | CSA | not specified | ETL Certified | CSA (Certificate No. 80296889) |
| Dimensions | 17.7"H x 17.7"W x 14.6"D | 17.12" x 13.12" x 3.12" | not specified | 10.96 x 7.4 x 2.52 in | 21 x 13 x 7 in | 21" H x 13" W x 7" D | not specified | 21" H x 13" W x 7" D |
| Use | Under Sink | not specified | Under Sink | not specified | not specified | not specified | not specified | not specified |
| Weight | 26.5 pounds | not specified | not specified | not specified | 21.2 pounds | 19.8 pounds | not specified | 21.2 pounds |
| Size | 6.5 Gallon | 240V/18kW | 2.5 Gallon | not specified | not specified | not specified | 240V/11kW | not specified |
| Color | white,blue | Gray | White | White | Metallic Silver | Bright Silver | Gray | Silver |
| Model | ES700 | ET180 | ES250B | ET060 | CZ360LP | CZ264LP | ET110 | CZ360NG |
Thermomate Models at a Glance
Thermomate splits its lineup by fuel source and installation needs. Electric models like the 6.5-Gallon Under-Sink Mini-Tank and the 18kW Tankless Heater suit standard 120V or 240V circuits. These units offer compact storage or on-demand heating without venting requirements. The 6.5-Gallon Mini-Tank works well for under-sink use, while the 18kW unit handles higher flow rates for homes with adequate electrical capacity. Gas options provide steady heat for indoor setups. The 4 GPM Propane Heater and the 98,500 BTU Natural Gas model deliver consistent performance for households with existing gas lines. These units are ideal for single-shower or multi-fixture demand. You can choose based on your available utility connections and space constraints. Each category serves distinct household needs effectively.
Where Thermomate Fits
Thermomate covers specific niches rather than offering a universal solution. You can choose from small 2.5-gallon mini-tanks for single sinks or compact 6kW electric units. Mid-range options include 11kW and 18kW electric heaters for higher demand. Gas and propane models provide 75,000 to 98,500 BTU outputs. The range lacks large whole-home electric tankless units or outdoor-rated appliances. You also will not find commercial-grade high-flow models. This brand suits point-of-use applications and small households with existing gas or standard electrical infrastructure.
If you also compare fitness equipment, you can examine published specifications for the best water rowers.
How to choose the right thermomate unit
-
Match fuel to your home
Start by checking which energy source is available at your installation site. If you have existing gas lines, the Thermomate 98,500 BTU Natural Gas Tankless Water Heater offers steady on-demand heating for up to two fixtures. For homes without gas, electric models like the 18kW unit provide high output. Propane options, such as the 4 GPM Indoor model, suit small households with indoor hookups. Your choice depends entirely on the infrastructure already in place.
-
Check electrical capacity first
Electric tankless heaters require specific voltage and amperage ratings. The Thermomate 18kW Electric Tankless Water Heater demands an 80-amp electrical capacity to deliver 4.4 GPM. Lower wattage units, like the 6kW model, work for single-sink handwashing but need 240V power. Mini-tanks often use standard 120V outlets, simplifying installation. Verify your home’s panel capacity before selecting a high-wattage electric unit to avoid costly electrical upgrades or tripped breakers.
-
Decide on installation location
Your space constraints determine whether you need a mini-tank or a tankless unit. Under-sink installations suit the Thermomate 6.5-Gallon Mini-Tank, which fits in standard cabinets. Tankless models like the 11kW unit are compact and mount on walls, saving floor space. Indoor propane and natural gas heaters require ventilation clearance. Measure your available width and height carefully. The 6kW model is notably small at 7.5 inches wide, making it ideal for tight utility closets or under sinks.
-
Assess your hot water demand
Determine how many fixtures you need to run simultaneously. The Thermomate 18kW unit supports higher flow rates for multiple uses. The 4 GPM Propane model handles a shower and faucet together. For single-sink point-of-use applications, the 6kW Electric unit provides steady temperatures without wasting energy. If you only need hot water for one tap, a smaller unit suffices. Matching flow rate to your actual usage prevents overheating or insufficient hot water during peak times.
-
Consider temperature control needs
Precision matters for comfort and safety. The Thermomate 11kW Electric Tankless Water Heater offers precise 1°F temperature control for single-point setups. Propane models like the 75,000 BTU Indoor Heater also feature tight ±1°F control. This stability ensures consistent water heat without fluctuations. Check if the unit includes digital controls or sensors. Accurate temperature regulation protects your pipes and appliances from thermal stress while providing reliable performance for daily tasks.
Frequently asked questions
What is the best thermomate tankless water heater for under-sink use?
The Thermomate 6.5-Gallon Under-Sink Electric Mini-Tank is the top pick for point-of-use installations. It operates on standard 120V power, so you do not need high-voltage wiring upgrades. The unit measures 14.6 inches wide and 21.2 inches high. You can mount it on the floor or wall. This model delivers dedicated hot water without requiring complex electrical work.
Which thermomate unit provides the highest flow rate?
The Thermomate 18kW Electric Tankless Water Heater delivers up to 4.4 GPM. This high flow rate requires an 80-amp electrical capacity and 240V power. The unit features precise digital controls for temperature management. Its compact dimensions are 13.1 inches wide and 17.1 inches high. This model is best for homes with sufficient electrical service.
Does thermomate offer propane tankless water heaters for indoor use?
Yes, Thermomate offers two indoor propane models. The 4 GPM Propane Tankless Water Heater has a 98,500 BTU rating. It is suitable for running a shower and faucet together. The 75,000 BTU Indoor Propane Water Heater provides tight temperature control within ±1°F. Both units are designed for dedicated propane setups in small households.
What is the smallest thermomate electric tankless heater?
The Thermomate 6kW Electric Tankless Water Heater is the most compact electric option. It measures just 7.5 inches wide and 11.2 inches high. This unit is engineered specifically for single-sink point-of-use installations. It requires 240V power to deliver steady handwashing temperatures. Its small footprint helps you save valuable cabinet storage space.
Can I use a thermomate heater for natural gas?
Yes, the Thermomate 98,500 BTU Natural Gas Tankless Water Heater is available. It provides steady on-demand hot water for up to two fixtures. The unit uses natural gas and requires standard 120V power. It is designed for indoor installation in households with existing gas infrastructure. This model is the best natural gas choice on the list.
What is the best thermomate option for a single sink?
The Thermomate 11kW Electric Tankless Water Heater is ideal for single-fixture sinks. It delivers a steady 2.15 GPM output with precise 1°F temperature control. The unit requires 240V power and is gray in color. Its dimensions are 11.8 inches wide and 14.8 inches long. This model is best for low-flow bathroom applications.
How much space does the thermomate 2.5 gallon mini tank take?
The Thermomate 2.5-Gallon Under-Sink Mini-Tank Heater measures 13.2 inches wide and 18.9 inches high. It is designed for single-sink point-of-use installations. You can use it for booster setups or dedicated heating. The unit plugs into standard 120V power. Its compact size makes it an effective choice for tight under-sink spaces.