Pros and Cons of Point-of-Use Water Heaters: Top Models and Buying Tips

When it comes to hot water, waiting for it to arrive can be frustrating and wasteful. Point-of-use water heaters (POU) offer a solution by providing hot water instantly and precisely where you need it, without the need for long pipes.

But before you invest in a POU water heater, it's important to weigh the pros and cons and consider factors such as hot water demand and installation requirements.

In this article, we'll explore their advantages and disadvantages, highlight some of the top models available, and provide tips for making an informed buying decision.

Bosch point-of-use water heater (POU)
(photo: amazon)

What are the point-of-use water heaters?

Point-of-use water heaters are compact, energy-efficient devices that provide hot water directly at the location where it is needed, such as a sink, shower, or appliance, and to serve low volume fixtures in small apartments, cottages, garages, including mobile homes (RVs).

These units come in different sizes and types, including electric, gas, and tankless models. Electric point-of-use water heaters are the most common and are often installed under sinks or in small spaces. Gas-powered models are more powerful and can serve larger households, but they require venting and professional installation.

The main advantages of point-of-use water heaters are that they provide hot water instantly, eliminate the need for long hot water pipes, and reduce standby energy losses.

They can be used in new or added to existing systems (retrofits), often installed under the kitchen or bathroom sink. This is why they are also called under-sink water heaters.

However, they may not be suitable for high-demand applications, such as multiple showers or large tubs, as they may not provide enough hot water. Additionally, they require a dedicated electrical circuit or gas line and professional installation, which can increase the upfront cost.

Top-selling models

Top 3 selling POU tank-type models

• Bosch Tronic 3000 T
• Ecosmart ECO MINI 2.5
• Stiebel Eltron SHC 2.5

Top 3 selling POU tankless models

• Ecosmart POU 6
• Stiebel Eltron DHC-E 8/10
• Rheem RTE 13

Advantages

Point-of-use water heaters have several advantages compared to other types. If you live in a house with a sink far from the central unit and experience a long wait time for hot water, installing a point-of-use heater can reduce the wait time, water usage, and energy consumption. They are nearly 100% energy efficient.

POU heaters can also be used when a tank-type or tankless water heater does not serve a remote sink and retrofitting is too expensive or impractical. In large buildings, contractors may choose several POU units instead of a high-capacity tank model, significantly minimizing the wait time for hot water delivery. As the units are dedicated to only one location, they provide steady hot water flow.

Additionally, when these mini tanks are installed in line with tankless models, they operate as a buffer, minimizing temperature fluctuations known as "cold water sandwich" and increasing comfort. When installed as recommended, POU water heaters can actually save money, particularly when installed close to the shower, washing machine, and kitchen sink. The idea is to minimize the distance between the heat source and the faucet.

Finally, another great advantage is the ability to adjust the water temperature on the spot, provided the units are installed with easy access.

Disadvantages

• POU units are not suitable for applications with high hot water demand.
• Should not be used as the backup for the solar heating systems and geothermal heat pumps, as they cannot meet the demand when these do not operate.

Types

As mentioned previously, there are two types of point-of-use water heaters: mini-storage tank-type, with a capacity ranging from 2 gallons up to 30 gallons, and tankless units with a low water flow but a continuous supply of hot water.

Tankless point-of-use heaters are rated by the number of gallons per minute they can provide, while tank-type units are based on their tank capacity.

POU tank-type units are similar to large and tall models but typically have only one heating element with a thermostat.

Good examples of electric mini-tank type units include the Ariston from Bosch, SCH from Stiebel Eltron, and Rheem 30-gallon, while popular electric tankless POU models include Tempra from Stiebel Eltron and EcoSmart.

Popular manufacturers

• Eemax
• Stiebel Eltron
• EcoSmart
• Bosch
• Rheem

Features

The best point-of-use water heaters come equipped with components that extend the heater's lifespan, improve performance and efficiency, save on energy, and even provide automatic control.

Most point-of-use heaters feature a metal tank, but there are also models with plastic tanks, such as Marathon models, that are resistant to corrosion.

Heaters usually have only one screw-in style heating element, with a power range from 1.5 to 2 kW, which effectively transfers heat directly to the surrounding water.

Storage tank-type units are protected from the corrosive effects of hot water by using a ceramic/glass coating combined with an anode rod.

Fully automatic control is achieved by using a surface-mount thermostat with ECO, which is installed for safety in situations where temperatures exceed normal levels.

Smaller units typically use 120V and come with a cord that can be plugged into any standard outlet, while 240V models include a junction box for easy installation.

Installing tips

With its space-saving design, the point-of-use water heater is perfect for installation in areas with limited space where standard types cannot be installed.

These mini electric heaters can be mounted almost anywhere, such as in kitchens and bathrooms under the sink, inside cabinets in apartments and condos, hanging on walls, standing on floors, in camps and recreational properties, in stores, offices, and other places as wash stations.

The size of the POU heater needed depends on the area where it will be installed and the power supply available. Smaller units are mainly used for tasks like hand-washing, while larger models with higher flow rates are used for tasks like dish-washing, shaving, showering, and even supplying more than one fixture.

Note: Always follow the manufacturer's recommendations and manual when installing the point-of-use water heater. You can install the heater as an independent unit or as part of an in-line installation with other heaters, such as tankless heaters, for example.

These heaters can be installed directly at the sink, on the cold supply line, and as close as possible to the hot tap, eliminating the need for recirculating lines and pumps. Some models can be installed horizontally, while others must be installed vertically.

Summary

Point-of-use water heaters are an excellent choice for homes and businesses that require a small amount of hot water. They are especially suitable for situations where traditional cylinder-type heaters take up too much floor space or where a buffer is needed to support tankless water heaters.

One of the main benefits of POU water heaters is that they can be installed close to the point of use, which results in shorter pipes and faster delivery of heated water. This, in turn, leads to energy, space, time, and water savings, as well as increased comfort.

In summary, if you need a small amount of hot water and don't have enough space for a traditional water heater, a POU water heater is an excellent solution. With its many benefits, including energy savings, space savings, and improved comfort, it's a smart investment for any home or business.

FAQ

When to consider POU heaters?

POU heaters are ideal for areas where traditional water heaters are not suitable due to their compact size. If your household or business only requires a small amount of hot water, a POU heater can be a more efficient and cost-effective solution.

Additionally, for properties in remote locations without access to a centralized hot water system, these heaters can provide a convenient and reliable source of hot water. They can deliver hot water almost instantly, making them an excellent choice for applications where hot water is needed quickly.

Can point-of-use water heaters be used for showers?

Yes, point-of-use water heaters can be used for showers, but it depends on the unit's size and flow rate. Smaller POU units with lower flow rates are suitable for hand-washing and providing hot water to a single fixture, while larger units with higher flow rates can provide enough hot water for showering and even supplying more than one fixture. It's essential to choose the right size and type based on your hot water needs to ensure a comfortable and adequate supply of hot water.

Can point-of-use water heaters be installed as part of an in-line installation?

Yes, point-of-use water heaters can be installed as part of an in-line installation, together with other heaters such as tankless water heaters. They can be installed directly at the sink, on the cold supply line, and as close as possible to the hot tap, eliminating the need for recirculating lines and pumps.