Are under sink water heaters worth it?

Having an endless supply of hot water on demand is a luxury many homeowners wish they had. Installing an under sink water heater can provide this convenience by giving you instant hot water right from the tap. But are these compact heaters really worth the investment?

What is an under sink water heater?

An under sink water heater, also called an instant hot water dispenser or point-of-use water heater, is a small tankless water heater that mounts under the sink. It heats water on demand as it flows through the unit, providing a constant supply of hot water.

Under sink water heaters connect directly to the hot and cold water supply lines under your sink. When you turn on the hot water tap, cold water flows into the unit. An electric heating element or gas burner instantly heats the water before sending it through the hot water line to the faucet. The temperature is typically adjustable from warm to very hot.

Benefits of under sink water heaters

There are several benefits that make under sink water heaters an appealing option for many homeowners:

• Endless hot water: Unlike conventional tank heaters that can run out of hot water, an under sink heater provides hot water on demand continuously.
• Faster hot water delivery: You don’t have to wait for water to heat up because the heater instantly warms the water as it flows through.
• Energy efficiency: Tankless heaters only use energy when activated, avoiding the standby energy losses of tank models.
• Compact size: The small size makes under sink models easy to install in limited spaces.
• Lower operating costs: The on-demand operation and efficiency of under sink heaters can reduce energy usage and monthly bills.
• Simple installation: The units mount under the sink and connect to existing pipes, requiring minimal plumbing work.
• Point-of-use convenience: Hot water is instantly available right where you need it, at the tap.

Drawbacks of under sink water heaters

While under sink heaters provide convenience and efficiency, there are some downsides to consider:

• Upfront costs: The units can be expensive compared to conventional water heater models.
• Limited hot water capacity: The small size supplies enough hot water for a single sink, but not whole home needs.
• Space requirements: You need 6-18 inches of open cabinet space under the sink to install the unit.
• Electrical requirements: Electric models need a dedicated circuit rated for the heater’s power demands.
• Temperature limitations: Most under sink heaters only heat water to 120-140°F, while tank heaters can reach 140°F.
• No tank reserve: There is no stored hot water capacity for high demand periods.
• External power venting: Gas-fired models require venting the exhaust gases outdoors.

Cost of under sink water heaters

Under sink water heaters range in price from about $150 up to $500 or more, depending on the fuel type, power output, and extra features. Here are the typical costs for popular models:

Type	Power	Typical Cost
Electric under sink heater	2-6 kW	$150 – $350
Gas under sink heater	36-200 kBTU/h	$200 – $500

The fuel type and power output determine how quickly the heater can heat water. Electric models provide 2-6 kW of heating power. Gas-fired heaters range from 36,000 BTU/h for small units up to 200,000 BTU/h for high demand applications. The more power, the faster you get hot water, but also the higher the purchase price.

Installation cost

You can install an under sink heater DIY or hire a plumber. The installation cost averages $150-$300 if you have a handyman do the work. Plumbers typically charge $200-$500 to install a unit. Here are the key steps they will perform:

• Shut off water supply lines and drain plumbing.
• Mount the small water heater unit under the sink.
• Connect hot and cold water supply lines to the heater.
• Connect the hot water outlet line to the faucet.
• Plug in electrical cord or connect gas supply line.
• Check for leaks and verify proper operation.

The heater tap into your existing under sink plumbing. No major re-piping is required in most cases. The electrical or gas supply must also be nearby.

Energy costs

Since they only heat water on demand, under sink heaters can reduce energy usage and costs. An electric heater that replaces a medium-sized tank water heater may save $75 or more per year on electricity. Gas-fired models can reduce gas usage by 30% compared to a conventional heater.

The chart below compares average yearly energy costs for an under sink heater versus a medium capacity tank model.

Heater	Energy Use	Energy Cost @$0.12/kWh
Medium tank heater	4800 kWh	$576
Under sink heater	2400 kWh	$288

Your actual savings depend on your hot water usage, fuel costs in your area, and the size of the existing water heater the under sink unit replaces. The energy savings can offset some of the higher initial cost of the heater over its lifespan.

Lifespan

Properly installed under sink water heaters typically last 5-10 years. The lifespan depends on several factors:

• Water quality – Hard water and corrosive water can scale or corrode the inside parts.
• Use frequency – Heavily used units wear out faster.
• Maintenance – Regular flushing and cleaning extends lifespan.
• Build quality – Better materials and construction increase longevity.

Look for a warranty of 5 years or longer, which indicates the product is built to last. With proper maintenance, an under sink heater should provide hot water for 5-10 years before needing replacement.

Maintenance

Under sink heaters require minimal maintenance. However, follow these tips to keep your unit running efficiently for years:

• Flush the heat exchanger annually to remove sediment that can build up internally.
• Clean the water filter regularly, if equipped.
• Check pipes and fittings for leaks annually.
• Keep the unit free of dust and debris that can build up inside the case.
• Have gas-fired heaters serviced every 1-2 years to keep the burner operating safely.

Also follow the maintenance instructions provided in your product manual. With periodic cleaning and checks, an under sink water heater will provide reliable service.

Safety precautions

Under sink heaters are very safe when properly installed and maintained. Follow these precautions for optimal safety:

• Choose a unit listed by a reputable testing agency like UL, CSA, or Intertek.
• Have a qualified plumber install the heater according to local building codes.
• Carefully follow the installation instructions.
• Keep electrical components away from water to prevent shock hazard.
• Ensure gas-fired heaters are correctly vented outdoors.
• Install a GFCI outlet if required for the electrical model chosen.
• Check for gas leaks on gas-fired units.
• Keep the heater accessible for maintenance and repairs.

Compact under sink heaters have an excellent safety record. Just take sensible precautions during installation and operation.

Should you choose electric or gas?

Under sink water heaters are available in electric or gas-fired models. The fuel type you choose depends on several factors:

• Energy cost – Choose electric if your electric rate is lower. Go with gas if you have lower priced natural gas.
• Existing fuel supply –It’s cheaper to match the power source you already use in your home.
• Venting – Gas models require outdoor venting the exhaust.
• Installation cost – Gas may require more extensive plumbing work.
• Operating cost – Compare costs of electric vs gas models based on local energy prices.
• Hot water demands – Electric can meet light needs, while gas provides more heating power.

In most cases, homeowners choose the under sink heater fuel that matches their current water heater and is most economical in their area.

Should you buy a tankless or tank model?

Under sink water heaters are available in tankless or small tank designs. Here’s how they compare:

• Tankless heaters – Heat water directly as needed. Provide an endless hot water supply but limited flow at a time. No tank losses.
• Small tank heaters – Keep a reserve supply of hot water in a miniature tank (2-5 gallons). Meet higher simultaneous demands but have some standby losses.

Tankless models are best for one-at-a-time uses like hand washing where continuous flow is less important. An under sink tank model maintains usable hot water capacity for times when you need more volume like filling a pot.

Choosing the right size

Manufacturers rate under sink water heaters by their maximum power level (wattage or BTU/h). Choosing the right size unit depends on your typical hot water demand. Here are some guidelines:

Demand	Recommended Power
Hand washing	1500 watts or 36,000 BTU/h
Single sink	2000-3500 watts or 100,000 BTU/h
Light kitchen duties	3000-4000 watts or 120,000 BTU/h
Medium kitchen duties	4000-6000 watts or 140,000-200,000 BTU/h

Oversizing your under sink heater won’t provide any benefit. Choose the right size based on your typical usage to minimize costs.

Where to install under sink heaters

The most popular place to install under sink water heaters is in the kitchen, since that’s where you need a high volume of hot water for cleaning and cooking. But under sink heaters work well in any location where you need hot water access, such as:

• Bathroom sink for faster hand washing or shaving.
• Bar sink to make cleaning glasses easier.
• Utility sink for washing up.
• Garage sink to conveniently wash your hands.
• Wet bar sink to quickly rinse glasses and tools.

Virtually any sink where you currently have plumbing lines for hot and cold water is a candidate for adding an under sink water heater. This provides point-of-use hot water while saving trips to a more distant sink.

Alternatives to under sink heaters

If an under sink heater doesn’t fit your needs, consider these other options for hot water access:

• Whole home tankless heater – Provides on-demand hot water to all sinks, showers, and taps.
• Instant electric hot water taps – Deliver instant hot water from a single tap.
• Hot water recirculating pump – Circulates hot water through your pipes back to the heater.
• Tankless coil in boiler – Uses an existing heating boiler to heat water.
• Hybrid heat pump water heater – Provides high efficiency and some heat recovery.

Consider your needs and budget to choose the best instant or tankless hot water solution for your home. An under sink model provides the convenience of instant hot water for a single location.

Conclusion

Under sink water heaters provide an affordable and effective option for gaining instant hot water access right where you need it most. While not a whole home solution, installing a unit under sinks where you use hot water frequently delivers convenience and can reduce energy costs.

The compact size, ease of installation, and point-of-use efficiency make under sink heaters a practical upgrade. For a busy kitchen, bathroom, or utility room sink, the endless on-demand hot water can make tasks faster and easier. Just size the heater correctly for the tap’s typical demands and install it with care to gain years of trouble-free performance.