Best Under Sink Water Heater Review

Why under sink water heater is a good solution for your hot water needs? Find popular models such as Ariston, Powerstar and InSinkErator for point of use service with the top features.

Under the counter water heater is a small appliance for instant water heating at home or office, at the point of service. Also known as instant water heaters for sink, they can save you lots of water, energy and cash when properly installed and used. The appliance is usually installed in kitchen sections or bathroom, under the sink or counter, for easy access and operation.

The Advantages

A good under sink water heater comes with lots of benefits for those who make use of it. One of the greatest advantages is that they provide instant hot water to the distant fixtures, therefore, shortening the wait time. This way you don't have to run long pipes from the central water heater; just plug this small water heater close to the faucet and enjoy an instant delivery.

Buying an instant water heater for sink brings the following benefits:

  • It reduces your heating cost up to 50% and reduces used energy and water waste.

  • The unit saves you money as it eliminates the need for expensive recirculating lines or pumps.

  • Under sink water heater saves water efficiently as it is used where it is needed, at the point of use; kitchen sink, bathroom, laundry, garage, small cabins, boats and RVs, offices...

  • Under the sink water heater serves one or two faucets max. mainly for doing dishes, hand washing or shaving.

  • You can choose one of the two different types; tank-type or tankless. Tank type has a limited tank size, usually from 2 gallons while tankless provide an unlimited water supply but with the restricted flow. Tankless models are heating water instantaneously as it flows through the unit and there is no stand-by heat loss.

  • Under sink water heater is a small, lightweight and compact unit that doesn't occupy too much of the space.

  • It’s easy to install since it comes with the quick installation guide.

  • They can be wall mounting or floor standing.

  • Under sink water heater is very reliable, safe and energy efficient.

  • It has a compact body and other easy-to-use features.

  • They offer safety feature for reliable and safe operation.

  • Desired temperature of the outgoing water can be set by using the temperature dial.

Buying and Installation tips

When looking for a quality under sink water heater to buy, you need to go for the popular brands that have a long tradition that usually come with quality features. The most important criteria when selecting the right mini water heater are:

  • Water flow rate (bathroom faucet allows an average 0.5 gpm; shower 1.5 to 3.0 gpm).

  • Incoming water temperature.

  • Activation flow rate.

  • Heating power in kW.

  • Available features such as the modulation, conveniently located thermostat, relief valve for safety.

  • Price and warranty.

They are available in various online shops. Buying the appliance is one thing, but installing is another different ball game. Here’s a quick general installation guide for most models.

  • Get the place you want to install the appliance ready. The unit should be mounted closer to the fixture; under the sink, under the countertop or in the cabinet. Make sure to allow proper clearance for correct draining, maintenance and service.

  • Gather your installation tools; required tools are usually recommended in the manufacturer's manual: adjustable wrench, screwdrivers, level...

  • Prepare and remove all the necessary plumbing components.

  • Follow the quick installation guide in the manual that comes with the appliance. Designate electrical outlet might be needed. Follow the steps for plumbing connections.

  • The water heater should have T&P valve installed.

  • Remove all debris and air. You have to do this after filling the appliance with water. You have to run the faucet for some minutes in order to get rid any air bubble in the water heater. Never put the heater ON unless you have filled it with water. If you do, serious damage might result.

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Popular Under Sink Water Heaters

There are lots of under sink water heater brands and models out there. Here are the popular ones:

Bosch GL2.5

Bosch GL2.5 Ariston is one of the best selling small tank-type water heaters that are installed under the sink.

under sink water heater ariston gl2.5

  • Ariston offers an elegant and modern Italian design with a space saving size.

  • Superior insulation provides higher efficiency.

  • Simple installation under the sink; it mounts on the cabinet wall or floor.

  • Ideal electric unit for one sink.

  • It uses one heating element with the power of 1.5 kW. Recovery rate is 7 gallons per hour.

  • Temperature range is from 65 to 145 F.

  • 6-year warranty on the tank.

  • Price: $170.

Pros and Cons. Great solution for people who are looking for fast hot water delivery. Hook-up is simple with good manual instructions. The heater requires dedicated electrical outlet. It is a good unit with simple operation but lacks of a dial for the temperature adjustments (actually it exists behind the cover and few screws). 2.5 gallon tank doesn't last long, but it is good enough for small jobs such as hand and face washing. The thermostat is not very accurate and trial-and-error adjusting is needed for the right water temperature.

InSinkErator W152

insinkerator w152 instant water heater for sinkInSinkErator W152 is the electric undercounter water heater that heats the water at the point of use, economically and efficiently. It is designed as the tank-type unit with the capacity of 2.5 gallons making it the right solution for small jobs, and if you want to avoid big tank-type heaters or running long pipes from the central unit.

With the recovery rate of 8.6 gallons per hour and adjustable temperature range of 100 to 160 F this unit is a great performer. InSinkErator W152 is also durable as it doesn't have elements that easily wear and corrode. The tank is made of bronze and is insulated for maximum heat retention and low standby heat loss.

You can buy InSinkErator W152 for approximately $220, and it comes with five-year limited warranty on the tank.

Pros and Cons. InSinkErator W152 is doing heating job pretty well, it heats the water almost instantly, but some complaints are found that the unit has a flimsy construction and that the temperature adjustment behind the front panel is not user-friendly and convenient to operate.

Bosch AE-12 PowerStar

powerstar ae 12 instant water heater for sinkBosch AE-12 PowerStar is a 12 KW tankless under sink water heater that is designed with the capacity of 2 gallons per minute for an endless supply of kitchen and bathroom sinks. As it doesn't have the tank, this unit, with the 4.9 pounds is very lightweight, making it easy to mount. This electric tankless unit needs lots of Amps (40) so 240 V is what is needed.

It sells for approximately $250, and it comes with five-year warranty on the heat exchanger.

Pros and Cons. According to the online reviews, Bosch AE-12 PowerStar is performing great, delivering hot water fast and within listed specification. People who used to wait for hot water 2, 3 minutes are having it now within seconds. The unit uses an expensive 6 gauge wire.

Other popular models can be found among:

  • Chronomite

  • Eemax

  • Rheem

  • Reliance

  • Stiebel Eltron Tempra

  • Titan

  • Hubbell


Under sink water heater is the electric appliance for instant water heating at home or office while saving an energy, water and money. It showcases in various brands and models and most of them can be purchased online and in stores such as Home Depot, Lowe's, Walmart... They are small, space saving and efficient and provide hot water instantly. Tankless type under the sink water heater is providing an endless supply while tank-type has a limited capacity.

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