Tankless Water Heaters: A Buyer’s Guide

Updated: Mar. 07, 2023

Is a tankless water heater for you?

indoor tankless water heaterVia The Home Depot

What is a Tankless Water Heater

Tankless water heaters take up much less space than storage water heaters as they heat the water directly. When you turn on the hot water, the cold water travels through a pipe and into the tankless water heater unit where it is heated by a gas burner or an electric element. This allows you a constant supply of hot water.

On average, tankless water heaters can provide 2 to 5 gallons of hot water per minute. Gas-fired tankless water heaters, according to energy.gov, can produce higher flow rates than electric models.

For those with large families who go through a lot of hot water, installing more than one tankless water heater is common. This will ensure there is always enough hot water available for showers, laundry and the dishwasher.

Tankless Water Heater Advantages

Tankless water heaters (also called “on demand” units or an instant hot water heater) use 30 to 50 percent less energy than units with tanks, saving a typical family about $100 or more per year, depending on water usage.

  • These units heat water only when you turn on the faucet.
  • They usually operate on natural gas or propane.
  • The main advantage is that they eliminate the extra cost of keeping 40 to 50 gallons of water hot in a storage tank, so you waste less energy.
  • They also offer a continuous supply of hot water, which is ideal for filling a big hot tub or a whirlpool.
  • They’re more compact than a standard water heater and mount on a wall.

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Tankless Water Heater Disadvantages

  • The primary disadvantage of on demand or instant hot water heaters is the upfront cost.
  • The smaller units that you often see won’t produce enough hot water to serve most households. They’ll only serve one faucet at a time—a problem if you want to shower while the dishwasher is running. There are larger units that can handle the demand of a whole family, but they are expensive.
  • But because tankless units have high-powered burners, they also have special venting requirements (a dedicated, sealed vent system, which requires professional installation). Natural gas burners often need a larger diameter gas pipe, which adds to the initial installation cost.

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Electric vs Gas Tankless Water Heaters

The biggest difference between electric tankless water heaters and gas tankless water heaters is their efficiency. Electric tankless water heaters are typically around 98 percent or more efficient while gas tankless water heaters are around 80-85 percent efficient. A gas tankless water heater can be cheaper to run and will typically last longer.

Electric Tankless Water Heaters

Tankless water heaters will free up space that a bulky water heater typically occupies. An electric tankless water heater will be more efficient than a tankless gas water heater but know that an electric model requires a lot of electricity. A whole house electric tankless water heater can use more than 25,000 watts of electricity, compared to 5,000 watts of electricity with a conventional water heater.

Gas Tankless Water Heaters

Gas tankless water heaters will last longer than traditional water heaters and they’re safer than conventional water heaters. One disadvantage is that if there is scale build up, a tankless water heater can automatically shut off.

The Bottom Line: Pricing and Installation

When you’re pricing a unit, be sure to get an estimate or firm bid on installation costs. This is not a do-it yourself project unless you have pro-level skills. You can find the best tankless water heaters at many home centers and plumbing specialty stores.

This WiseWater Tankless Hot Water Heater is available on Amazon today.

Figure A: Tankless Water Heater Details

When a hot water tap is opened, the heating elements turn on. Water is heated as it flows through the heat exchanger.

tankless water heater diagramFamily Handyman

Is a tankless water heater for you? Learn about them in this video:

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