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How do tankless water heaters work

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What are some of the benefits and drawbacks of tankless water heaters?

Tankless water heaters, commonly referred to as demand-type or instantaneous water heaters, heat water only when it is needed. You can save money because they don’t have the same standby energy losses as cold water standard water heaters. Here you’ll learn the fundamentals of tankless water heaters, such as how they work, whether they’re right for your home, and how to pick the right water heating system.


Tankless water heaters heat water directly without the necessity of a storage tank. Cold water enters the unit via a pipe when a hot water tap is switched on. A gas burner or an electric element heats the water. As a result, tankless water heaters deliver a steady supply of hot water. It is not necessary to wait for a hot water storage tank to fill. A tankless water heater’s output, on the other hand, restricts the flow rate.

2–5 gallons (7.6–15.2 liters) of hot water per minute is normal for tankless water heaters. Gas-fired tankless water heaters have higher flow rates than electric tankless water heaters. However, even the largest, gas-fired type may not always be able to supply enough hot water for many simultaneous uses in large homes. Taking a shower while also running the dishwasher, for example, could put a tankless water heater to the test. To meet simultaneous hot water demands, you can solve this problem by connecting two or more tankless water heaters in parallel. Separate tankless water heaters can also be installed for equipment that uses a lot of hot water in your home, such as a clothes washer or a dishwasher.

Other applications for demand water heaters include:

  • Hot tubs or bathrooms in the woods
  • Dishwashers and washing machines get a boost from this booster.
  • Booster for solar water heating systems.



For homes that use 41 gallons or less of hot water per day, demand water heaters are 24–34 percent more energy efficient than standard storage tank water heaters. Homes that use a lot of hot water — about 86 gallons per day — can save 8–14 percent on their energy bills. You can save even more energy by installing a demand water heater at each hot water outlet, saving between 27 and 50 percent.


Although a tankless water heater has a higher initial cost than a regular storage water heater, they often last longer and have lower operating and energy costs, which may offset the higher purchase price. The majority of tankless water heaters have a 20-year life expectancy. They also have easily replaceable parts, allowing them to last for many years. Storage water heaters, on the other hand, can last for ten to fifteen years.


Tankless water heaters eliminate the standby heat losses associated with storage water heaters. Despite the fact that gas-fired tankless water heaters have higher flow rates than electric ones, if the pilot light is left on all of the time, they can waste energy. When compared to a storage water heater, the reduction of standby heat loss can occasionally be counterbalanced. A gas-fired storage water heater’s pilot light heats the water in the tank, saving electricity.


The cost of maintaining the pilot light on a tankless water heater varies based on the model. Inquire about the amount of gas utilized by the pilot light on the model you’re considering. When purchasing a model with a standing pilot light, you can save energy by turning it off when not in use. Models that use a standing pilot light instead of an intermittent ignition device (IID) should also be evaluated. The spark ignition system used on some gas stoves and ovens is comparable to this technology.



Before acquiring a demand water heater, you should consider the following factors:

  • Size (number of gallons of water required)
  • Fuel type (gas or electricity) and availability
  • Efficiencies in the energy sector (energy star)
  • Initial Cost and Installation Costs


Proper installation and maintenance can enhance the energy efficiency of your demand water heater; consider hiring a professional installer.

The appropriate installation is influenced by a number of things. Fuel type, environment, local construction code requirements, and safety concerns, particularly with regard to gas-fired water heater combustion, are also factors to consider. As a result, it’s best to hire a certified plumbing and heating contractor to install your demand water heater. Keep the following in consideration while selecting a skilled installer:

  • Request expense estimates in writing.
  • Inquire about any suggestions.
  • For more information on the company, contact your local Better Business Bureau.
  • Examine whether the company will apply for a local permit if one is required, and whether they are conversant with local construction codes.

If you insist on installing your water heater yourself, start by speaking with the manufacturer. The manufacturer is usually able to provide appropriate installation and instruction manuals. Check with your city or municipality for information on obtaining a permit and, if appropriate, local water heater installation codes.

Water heater maintenance can help you get the most out of your water heater by extending its life and reducing efficiency loss. Your owner’s manual will provide specific maintenance instructions.


When your demand water heater is correctly installed and maintained, try these additional energy-saving ways to help cut your water heating bills. It is more cost-effective to install various energy-saving gadgets and systems with the water heater.

Tankless water heaters function in a unique way to heat your water.

Tankless water heaters use an electric element or a gas burner to warm the water as it travels through a pipe and into the device. This delivers a nearly endless supply of hot water, as well as immediate comfort and convenience. Unlike traditional water heaters, the hot water supply is not stored in the tank. As a result, a tankless water heater is a cost-effective conservation option. Continue reading to discover more about tankless water heaters and the information you’ll need to choose one that’s right for you.


Tankless Water Heater Flow Rate

The amount of hot water consumed per minute is measured in gallons (GPM). This is the amount of hot water a water heater can produce at a constant rate.

Add the GPM for all of the essential fixtures and appliances you’ll be utilizing at the same time to find out how much GPM you’ll need for your home.


The flow rate through the water heater must be at least 2.5 GPM if you use a bathroom faucet with a flow rate of 1.0 GPM and a shower head with a flow rate of 1.5 GPM at the same time.

Ground Temperature for Tankless Water Heaters

When choosing the best tankless water heater for your home, it’s vital to consider the temperature of the ground water. What is the temperature of the water you’re drinking? This information is needed to compute the temperature rise.

To gain an indication of average ground water temperatures, start with the forecasted coldest ground water temperature for your area on the map above. Then calculate how much your entering ground water temperature differs from the temperature you want your output to be. For the most part, you’ll want the water to be between 100 and 115 degrees.


The required flow rate is 2.5, and Atlanta’s groundwater temperature is 55 degrees. It is necessary to use a water heater with a minimum temperature rise of 45 degrees.

Additional Tankless Water Heater Considerations

Before choosing between gas and electric tankless water heaters, consider how you want the water heated. An electric element heats the water in a tankless electric water heater, whereas a gas burner heats the water in a tankless gas water heater.

On each tankless water heater, the maximum GPM flow rate for various needed temperature increase is specified. Once you’ve determined your peak water flow need in gallons per minute and the temperature rise you require, you may choose the best tankless water heater for your needs.

Below is a list of reasons why you should consider getting one for your home.


  • Tankless hot water heaters can provide a virtually infinite supply of hot water, allowing for long, relaxing showers or baths.
  • Self-diagnostic programs, innovative sensors that prevent the item from overheating, and automated shut-off systems are among the unique characteristics that protect the home from overheating.


  • Tankless designs are small and save space.
  • In new homes, retrofits, expansions, and vacation homes, outdoor sinks, jacuzzis, and pool showers are ideal.
  • Modern amenities like as digital display thermostats and remote controls are included in many.


  • The majority of models can help you save up to 40% on your family energy bills.
  • On average, a tankless water heater can last up to 20 years. This reduces the amount of waste sent to landfills and the amount of fossil fuels used to heat water.
  • There are also ENERGY STAR® certified models available.