Tankless undersink water heaters are a great option for providing on-demand hot water directly at the point of use under a sink. They heat water instantly as it flows through the unit, so you never run out of hot water. Tankless undersink heaters are compact, energy efficient, and can be installed under pretty much any sink in your home. But with so many models on the market, how do you choose the best one? Here we will discuss the key factors to consider when selecting an undersink tankless water heater so you can find the right one for your needs.
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What are the benefits of a tankless undersink water heater?
Tankless undersink water heaters offer several advantages over conventional tank style units:
- On-demand heating – Hot water is produced instantly and continuously as needed.
- Compact size – Small and slim, tankless heaters fit easily under sinks.
- Energy efficiency – Only heat water when needed so less standby energy loss.
- Endless hot water – Never run out even with consecutive uses.
- Lower operating costs – Use less energy than storage tank heaters.
- Easy to install – Simple DIY installation with basic plumbing skills.
With a tankless undersink heater, you’ll enjoy convenience, efficiency, and reliability right at the point of use. They are ideal for boosting hot water supply to tasks like washing hands, doing dishes, and more.
Key Factors to Consider
When selecting the best tankless undersink water heater, there are several key factors to keep in mind:
Power/Heating Capacity
The power or heating capacity needed depends on your hot water requirements. Tankless heaters are rated in kilowatts (kW) to indicate their maximum heating output. Choose a model with adequate power for your needs:
– For a single sink, 3-6 kW is usually sufficient.
– Larger units from 6-10 kW work for busier sinks or small apartments/offices.
– 10-20 kW capacity for commercial settings with high demand.
Undersizing your heater will result in diminished hot water flow.
Water Flow Rate
Flow rate, measured in gallons per minute (GPM), indicates how much hot water the unit can produce continuously. Make sure to pick a heater with a flow rate that matches your needs. Most residential undersink heaters have flow rates of:
– 0.5-1 GPM for hand washing sinks.
– 1-2 GPM for small kitchen sinks.
– 2-5 GPM for large kitchen/utility sinks or light commercial use.
Higher flow models above 5 GPM are also available. Match this spec to your expected water demand.
Activation Flow Rate
The activation flow rate is the minimum water flow needed for the heater to turn on and start heating. Look for a low activation rate around 0.3-0.5 GPM so the heater responds quickly when water starts flowing.
Temperature Settings
Many tankless heaters allow you to adjust the output water temperature, usually from around 90-140°F. Select a model with your desired temp settings. Most sinks only need 100-120°F water.
Safety Systems
Look for the following safety features when selecting a tankless undersink heater:
– Overheat protection – Prevents overheating if water flow stops.
– Temperature limiting valve – Regulates water temp for safety.
– Leakage protection – Automatically shuts off power if a leak occurs.
– Flow sensor – Detects water flow to initiate heating.
Size and Dimensions
Since you are installing the heater under your sink, pay attention to the size and dimensions. Compact mini models take up less space. Measure to make sure it will fit in your cabinet. Also check the inlet/outlet connection sizes.
Installation Requirements
Consider the electrical requirements and whether a voltage upgrade is needed. Most plug into a 120V grounded outlet. Larger models may need a 240V hookup. Also factor in any plumbing alterations needed during installation.
Reviews of the Top Tankless Undersink Water Heaters
Now let’s take a look at some of the best tankless undersink water heater models on the market and key info on each:
Ecosmart ECO 11 Electric Tankless Water Heater
- Power: 13 kW max
- Flow Rate: up to 1.5 GPM
- Dimensions: 6.5 x 13.75 x 3.75 in
- Activation Flow: 0.3 GPM
- Temp Settings: 60-140°F
- Safety Systems: Overheat protection, auto shutoff
The Ecosmart ECO 11 is a popular option for point-of-use applications like undersink installation. It provides on-demand hot water while using less energy than traditional models. Advanced self-modulating technology allows variable power usage based on hot water demand.
Rheem RTE 13 Electric Tankless Water Heater
- Power: 13 kW max
- Flow Rate: up to 1.5 GPM
- Dimensions: 3.75 x 6.5 x 13 in
- Activation Flow: 0.4 GPM
- Temp Settings: 85-125°F
- Safety Systems: Overheat protection, flow sensor
This Rheem model is engineered for single point applications like undersink installations. It has an advanced flow sensor to detect water flow and intuitive controls for setting your desired temperature. The compact and lightweight design simplifies mounting under your sink.
Bosch ES2.5 Electric Mini Tank Water Heater
- Power: 5.5kW max
- Flow Rate: up to 1.3 GPM
- Dimensions: 13.75 x 3.75 x 10.25 in
- Activation Flow: 0.4 GPM
- Temp Settings: 60-140°F
- Safety Systems: Overheat protection, leak detection
The Bosch ES2.5 offers point-of-use convenience in a mini tank design. It maintains a constant 70°F temp then heats water on demand when activated. Glass-lined tank resists corrosion and integrated thermal efficiency helps reduce heat loss.
Stiebel Eltron Tempra 15 Electric Tankless Heater
- Power: 15 kW max
- Flow Rate: up to 3 GPM
- Dimensions: 8.5 x 17 x 3.75 in
- Activation Flow: 0.5 GPM
- Temp Settings: 86-140°F
- Safety Systems: Leak detection, temperature limiting valve
The Tempra 15 model from Stiebel Eltron provides higher capacity for increased demand. Advanced flow control technology maintains steady temperature even with simultaneous water draws. It also has self-modulating power and a vacation setting to maximize efficiency.
Camplux ME40 Mini Tankless Electric Water Heater
- Power: 4.4 kW max
- Flow Rate: up to 1.32 GPM
- Dimensions: 11 x 4 x 13.5 in
- Activation Flow: 0.4 GPM
- Temp Settings: 80-120°F
- Safety Systems: Overheat protection, auto shutoff
A budget-friendly option, the Camplux ME40 provides on-demand hot water in a compact mini tank design. Simple installation and front removable panels make maintenance straightforward. Good for single low-flow sinks.
Conclusion
When selecting a tankless undersink water heater, be sure to match the power, flow rate, and activation specs to your sink’s hot water requirements. Compact mini tankless heaters from brands like Ecosmart, Rheem, Bosch, Stiebel Eltron and Camplux are all good options that can provide energy efficient under sink hot water on demand. Consider your budget, capacity needs, and ease of installation to choose the best tankless undersink heater for your home or office. Proper sizing and setup will lead to endless hot water right where you need it.