ThermoMate ES250 Mini Tank Water Heater 2.5 Gallon
- Capacity: 2.5 gallons
- Wattage: 1440 watts
- Power Source: Battery
- Maximum Temperature: 149 °F
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
The Incoloy heating element and thick insulation make this a durable-leaning pick for one sink, provided the 1/2 inch fitting matches your lines.
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ASIN: B08BFL66GJModel: ES250Category: Water Heaters
Overview
Thermomate's ES250 packs a 2.5-gallon tank into a compact cube meant to live under a sink, counter or cabinet and supply hot water to that single fixture on its own 120-volt circuit.
It uses a 3-layer, porcelain enamel glass-lined tank and an Incoloy 800 stainless steel heating element rather than the more common copper element, a spec Thermomate ties to better corrosion resistance and a 99 percent heating efficiency figure. At 30mm, the insulation is on the thicker side for this size class, which should help it hold temperature longer between draws. The 1/2 inch NPT connection is narrower than some competing 2.5-gallon units that use 3/4 inch, worth checking against existing supply line fittings before buying.
- 2.5-gallon tank, 1440W at 120V
- Incoloy 800 stainless heating element
- 50-149 F adjustable thermostat
- UL listed, 150 PSI max
Who it's for
Works for a single remote sink, RV galley, salon station or shop washroom needing a small, self-contained hot water supply. Not intended to serve more than one fixture.
Pros and cons
- Incoloy 800 heating element resists corrosion better than copper
- 30mm insulation for better heat retention
- UL listed with ASME/ANSI/CSA-approved T&P valve
- Compact 12.95 inch cube fits tight spaces
- 1/2 inch NPT connection may need adapting to 3/4 inch lines
- Only 1-year warranty on parts versus 3 years on the tank
- 2.5 gallons limits it to one fixture at a time
Performance notes
The Incoloy 800 heating element is the standout spec here: Thermomate rates it as four times more corrosion resistant than copper and more efficient under high temperature and pressure, which should extend service life versus a basic copper-element tank. The 3-layer glass lining and extra-thick anode rod target scale and rust inside the tank itself, and the unit is rated to withstand 10,000 impulse cycles in testing. Thermostat range runs 50 to 149 F, with a 150 PSI maximum pressure and a UL-listed T&P relief valve for overpressure protection.
Specifications
| Brand | thermomate |
|---|---|
| Model | ES250 |
| Dimensions & fit | |
| Item Weight | 15.4 pounds |
| Item Depth | 11.5 inches |
| Item Dimensions W X H | 12.9 × 16.5 inches |
| Capacity & performance | |
| Capacity | 2.5 gallons |
| Maximum Temperature | 149 °F |
| Heat Output | 1440 watts |
| Power & efficiency | |
| Wattage | 1440 watts |
| Power Source | Battery |
| Voltage | 120 volts |
| Construction & materials | |
| Material Type | Stainless Steel |
| Color | White |
| Compatibility & installation | |
| Mount Type | Protruding |
| Included components | |
| Number Of Packs | 1 |
| Included Components | R&P Relief Valve, Mounting Kits, User Manual |
| Other details | |
| Maximum Pressure | 150 psi |
| Number Of Items | 1 |
| Style Name | 2.5 Gallon |
| Special Features | Corrosion resistant tank, UL Certified |
| Item Type Name | Kitchen Water Heater |
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Frequently asked questions
What size water connection does the ThermoMate ES250 use?
It uses a 1/2 inch NPT water connection, narrower than the 3/4 inch fitting on some other mini tanks in this size range.
How long is the warranty?
Thermomate covers the tank for 3 years and parts for 1 year, with 24-hour customer service listed.
What are the dimensions and weight?
It measures 12.95 x 12.95 x 11.5 inches and weighs 15.4 pounds, sized to mount under a sink, counter or cabinet.