ThermoMate ES400 4-Gallon Mini Tank Water Heater, 120V Plug-In

A 4-gallon preheated tank keeps hot water close to the fixture, helping reduce the wait at a sink that is far from a main water heater. The ThermoMate ES400 is designed for point-of-use service and small hot-water needs.

Its compact format can be mounted on a wall or placed on the floor under a sink or counter. The plug-in connection operates at 120V, making it a practical choice for a dedicated sink installation.

Choose from three thermostat settings within a 50°F to 149°F range. A freeze mode and high-temperature limit protection add useful control as the unit heats and stores water.

Best use cases

Use the ES400 to supply a kitchen, bathroom or utility sink where hot water from a central heater takes time to arrive. For example, in a side room or garage, placing a small tank near the faucet gives that fixture its own stored supply. The manufacturer describes this type of heater for a single application and small loads, rather than shower service.

A mini-tank stores a reserve of heated water for use at the nearby fixture. That makes it a different approach from a tankless point-of-use heater, which heats water as it flows through the unit. The ES400 suits customers who want a compact reserve under a counter, with wall or floor mounting options.

Why it makes sense

The glass-lined tank has an enamel coating to support insulation and help prevent leaks. The unit is rated at 1,440W and 120V, with thermal efficiency listed as up to 99%. Its 4-gallon capacity provides a ready supply for routine sink tasks, while point-of-use placement helps bring hot water closer to where it is needed.

Buyer feedback often appreciates the straightforward installation and the convenience of having hot water near the fixture. Comments about heating time vary, and some buyers raise durability concerns. These perspectives can help set expectations while the product’s practical appeal remains its compact stored-water design for small, local demands.

Key points

The ES400 measures 14.5" W x 14.5" H x 12.9" D and can be wall- or floor-mounted. It uses 1/2" NPT water connections, has a maximum water pressure of 150 psi, and connects by plug-in power. A temperature and pressure relief valve, mounting kits and user manual are included. The unit is UL Listed.

The thermostat offers three temperature levels, with a stated range of 50°F to 149°F. Freeze mode and high-temperature limit protection add practical controls for a small tank installed near a sink. Its dimensions make it suitable for planning an under-counter location where a dedicated hot-water supply can improve everyday access.

Is it worth it?

The ThermoMate ES400 is a focused choice for a sink or other single point of use that needs a nearby supply of stored hot water. Its 4-gallon capacity, plug-in 120V operation, adjustable thermostat and wall-or-floor mounting give customers useful flexibility when fitting a compact mini tank into a small-load setup.