What Is a Tankless Water Heater?
A tankless water heater heats water on demand, giving you hot water only as you need it. Depending on the model, a tankless water heater can supply hot water for your entire home or just a single point, such as a shower, sink or appliance. These water heaters are compact enough to allow installation in out-of-the-way spaces like in a closet or on an exterior wall.
Selecting a Power Source
Tankless water heaters are designed to provide an endless source of hot water when sized properly, helping you save on energy since you’re not storing, heating and reheating the same water. They come in natural gas, propane or electric models, so you can choose the model that fits the energy source you already have and your personal preference.
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Deciding on Condensing or Non-Condensing Gas Tankless Water Heater
What is the difference between condensing and non-condensing gas tankless models? Condensing gas tankless maximizes system energy by using a dual heat exchanger. Non-condensing models only have one heat exchanger. Condensing systems are more energy-efficient as less heat is lost in the process of heating the water.
How Does a Tankless Water Heater Work?
When you open a hot water tap or start the dishwasher, a tankless water heater recognizes the need for hot water and starts the heating process. The unit then calculates the incoming water temperature and uses it to determine how much heat the burners must produce to deliver water at the desired temperature. Once demand ceases, the tankless water heater shuts down and stops using energy, waiting until you need more hot water to start heating again. The end result is that you’re no longer limited to the amount of hot water available in your tank.
Benefits of a Tankless Water Heater
A tankless water heater doesn’t limit you to the amount of hot water a storage tank heater can hold. Whether you're washing the dishes, laundering clothing and towels or drawing a hot bath, tankless water heater technology instantly supplies the hot water your lifestyle demands. There are other benefits as well.
Lower Energy Bills
Take advantage of greater energy efficiency with a tankless water heater compared to a standard gas tank water heater. These units have a highly efficient design because they only heat water when needed.
Longevity
Tankless water heaters typically last up to 20 years with proper maintenance, which is often twice as long as a typical tank-style unit. The expanded lifespan means you typically spend less money on repairs and replacements.
Space Savings
Traditional water heaters can take up to 16 square feet of valuable floor space. Many tankless water heaters are about the size of a carry-on suitcase; you can install these units on a wall inside or outside your home, freeing up valuable storage space
If you're having trouble deciding which tankless water heater is best for your home, our Water Heater Finder walks you through every step to help you find the best option.
Choosing the Right Tankless Water Heater
A tankless water heater gives you hot water on demand, but knowing how to pick a tankless water heater that’s right for your home requires some forethought. Start by determining what size tankless water heater you need. Water heaters that are too small typically don’t provide an adequate amount of hot water for your home’s needs, while a unit that’s too large means unnecessary costs.
Choose a tankless water heater that can easily handle the peak hot water demand in your home. To do this, you must know how much incoming water the tankless water heater needs to heat to take care of the demand. That’s where understanding the flow rate and desired temperature rise factor in.
The flow rate measures the amount of water that flows from a fixture or appliance in gallons per minute (GPM). Likewise, temperature rise is the difference between the groundwater temperature and the desired hot-water output temperature. When it’s time to buy a tankless water heater, arm yourself with the flow rate and temperature rise, but also look at sizing charts and consider your overall budget to guide you in choosing the best unit to suit your needs.
Flow Rate (GPM)
To estimate your hot water needs, determine how many devices the water heater will support. List the total number of appliances or fixtures you typically use simultaneously during peak demand. For example, you might need to use the kitchen faucet for washing dishes, a clothes washer for laundry and a shower faucet at the same time. Once you’ve decided how much on-demand hot water you need, add up each individual flow rate for the total flow rate.
Locate the flow rate in the manufacturer’s manual for the fixture or appliance (shower head, dishwasher, washing machine, etc.), or check for the GPM stamped directly on the item. You can also easily calculate the GPM of an appliance or fixture with a bucket and timer using the following formula: 60 divided by the number of seconds it takes to fill a 1-gallon container with water from the appliance or fixture. Here are some sample flow rates.
Average GPM Usage for Common Appliances and Fixtures
Based on the chart above, the total flow rate for peak usage while using the shower, kitchen sink and a high-efficiency washing machine is 6.0 GPM.
Temperature Rise
Groundwater temperature varies throughout the country and can range from the mid-30s to the upper 70s, measured in Fahrenheit. North America is broken into three climate zones with average groundwater temperatures:
- Northern Zone: 37 degrees to 51 degrees
- Central Zone: 52 degrees to 61 degrees
- Southern Zone: 62 degrees to 77 degrees
Typical internal home water temperature ranges from 110 degrees to 120 degrees. To determine the temperature rise, subtract the incoming water temperature from the desired internal water temperature. For example, if the incoming water temperature is 57 degrees and your desired shower water temperature is 120 degrees, the temperature rise is 63 degrees.
Your Budget
Keep in mind that tankless water heaters are typically more expensive than their conventional counterparts. While traditional tank water heaters can start at around $500 and go up to $1000 or more, tankless water heaters designed to supply a whole home typically start at around $1,000 or more. Prices vary widely by type and location, but you can expect the initial cost of a tankless model to be higher. These units can, however, save money over time with energy efficiency as well as lower maintenance and repair costs. Buying a tankless water heater may be the more economical option for many homes.
The cost of tankless water heater installation will depend on whether your home is already designed to support a tankless water heater, if your plumbing system will need to be upgraded and the labor costs for your area, among other factors.
Types of Tankless Water Heaters
There are two common types of tankless water heaters. Take a look at the options so you can decide which is best for your needs.
Point of Use Tankless Water Heaters
Sometimes, an area of your home needs an extra boost of hot water. That's where a compact point of use tankless water heater can help. These small, tankless heaters are typically electric models and are helpful near a room or appliance that needs additional hot water. For example, if you have a hot tub that uses electric heat, you can install a point-of-use water heater nearby. These units are also helpful for additions and expansions to an existing home. To save space, select a unit that installs easily in a cabinet or compact closet.
You can also look for electric tank water heaters and tankless gas water heaters with point-of-use technology for added flexibility in installation and added convenience.
Whole-Home Tankless Water Heaters
Some gas and electric tankless water heaters can deliver enough hot water for an entire household.
Whole-home gas tankless water heaters typically range in sizes from 140,000 BTU to around 199,000 BTU; choose the appliance capability based on the amount of hot water you need for a home or business. You can find:
- Tankless water heaters designed for one or two people
- Tankless water heaters for families of three or four
- Tankless water heaters for families of five or more
Whole-home electric tankless water heaters are available as 240-volt units with kilowatt (kW) ranges of about 14 to 32 kW. The higher the kilowatt rating, the more hot water the water heater can deliver.
How To Install a Tankless Water Heater
You may be able install some electric tankless water heaters yourself, but first check national and local codes (ex. building, electrical, plumbing, gas). Codes may require that a licensed professional handle water heater installation. Follow the codes for your area and the instructions for your appliance. If you aren’t comfortable installing a tankless water heater yourself, Lowe’s offers professional installation options for most new units.
Installation steps typically include:
- Choosing a location for the unit that’s near both a water inlet and an electrical or gas connection
- Shutting off the power or gas and the water supply to the area and verifying that they’re off
- Disconnecting and removing your existing water heater
- Prepping the new tankless water heater for installation per the manufacturer’s instructions
- Installing any new water lines necessary for operation
- Double-checking all the fittings
- Correctly connecting the unit to the power or gas supply
- Installing any ventilation required for the tankless water heater
- Mounting the unit in the desired location
- Connecting the water lines
- Turning the water and power or gas back on
- Checking to ensure the unit operates properly
- Making temperature adjustments as needed
- Double-checking all the lines and ventilation to ensure smooth operation
Maintaining the Tankless Water Heater You Choose
While tankless water heaters are typically low maintenance, you still need to perform a few basic tasks annually to ensure energy efficiency and safe operation. You should follow the maintenance steps in the manual for your specific model, but here are some general must-do preventative maintenance tasks:
- Cleaning the Filter: Tankless water heaters have inlet filters that keep debris out of the unit, and these filters require regular cleaning. Removing debris reduces risks of clogging and ensures water flows through your unit uninterrupted.
- Monitor Water Pressure: Monitor the water pressure regularly to ensure it stays in the optimum range noted in the manufacturer’s guidelines.
- Inspect the Ventilation System: If you choose a tankless water heater that uses natural gas or propane for power, check the ventilation system annually. Look for obvious problems like obstructions, blockages and loose connections, and inspect closely for signs of damage or corrosion.