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The Pros and Cons of Tankless Water Heaters

Tankless water heaters can save energy, but at a higher initial cost and they serve hot water one faucet at a time—so someone gets a cold shower if multiple showers are running.

By the DIY experts of The Family Handyman Magazine

The Pros and Cons of Tankless Water Heaters

Tankless water heaters can save energy, but at a higher initial cost and they serve hot water one faucet at a time—so someone gets a cold shower if multiple showers are running.

Tankless water heater details

A tankless water heaters uses 30 to 50 percent less energy than units with tanks, saving a typical family about $100 or more per year, depending on water usage. Tankless units (also called “on demand” 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.

The primary disadvantage 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. Larger units that can handle the demand of a whole family, but 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.

The bottom line: 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 tankless water heaters at many home centers and plumbing specialty stores.

Figure A: Tankless water heater details

Artwork Courtesy of Bosch Water HeatingFigure A: Tankless water heater details

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.

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Comments from DIY Community Members

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1 - 6 of 6 comments
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February 05, 3:35 PM [GMT -5]

i love the tankless water heaters.. on the 9th of jan, i had a larger unit installed. it consists of 3 heating elements instead of the 2 I had originally . two additional breakers were added to the electric box. the problem im encountering is when the hot water is turned on the water tank is knocking or banging for each element, is this normal? plumber suggested that i live with the sound. please help . stell scerbo

November 15, 10:21 AM [GMT -5]

I have a tankless water heater that is posessed!! Everytime I am naked and ready to get in the shower it has to be reset and is flashing number 12 down in the basement. It rarely happens to anybody but me and in my bathroom which is the furthest from the unit. If I turn the sink hot water on first and then when it is hot I turn on the tub faucet then it works. Help!!

July 16, 8:27 AM [GMT -5]

My son bought a Bosch tankless water heater and is having problems with it holding the temp. He has called Bosch and they said any plumber should be able to fix it. Well after spending $$$ on a repairman, it is still not fixed and they are leery about hiring another plumber. They were told to flush it out but do not know how. Would you be able to explain how to do this?

December 08, 1:34 PM [GMT -5]

We were told not to buy one since the area has a high concentration of lime and chemicals in the water. I mentioned that we have a water softener. The plumber indicated that it will still wear out in less time than an normal water heater. Comments?

November 23, 3:19 PM [GMT -5]

I purchased one last year and I love and hate it. The Pros are when we have several showers in a row, we have endless hot water.

The cons are that it takes 2-3 minutes of running the water on full force to get the first hot shower. If the first user adjusts the faucet temperature, the water heater gives a wall
of cold water. It only lasts a minute but it's really cold. That only happens once.
.
It takes time for the user to remember how to use the on-demand water. Normal water heaters give hot water a bit sooner. The energy saved is a big plus vs the water that is wasted on warm up.

It has taken time to learn how to use the system. We have adjusted.

January 20, 9:35 PM [GMT -5]

Here is another point that needs to be made. These water heater also might require a larger gas service line. Mrhappyhammer

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