Ask Angie's List: What do I need to know about tankless water heaters?

A tankless heater is usually mounted on a wall, requiring much less space than a tank. (Dreamstime/TNS)
A tankless heater is usually mounted on a wall, requiring much less space than a tank. (Dreamstime/TNS)

If you're thinking of replacing your traditional hot water heating tank, you've probably heard about tankless heaters. But is it right for you? Here's a rundown of what you can expect.

Tankless water heaters, also known as on-demand heaters, will provide hot water only as needed. Because the water is heated as it's used, they don't produce the energy loss associated with traditional heaters, which must keep the water hot until used.

They can only produce hot water at a given flow rate, usually 2-5 gallons per minute. (Generally speaking, gas-powered heaters produce a higher flow rate than electric ones.) When there's only one water source running, this usually isn't a problem. However, if you're running multiple water flows, each of them will be slowed down, especially high-usage appliances such as filling a bath, running the dishwasher and running laundry at the same time.

These heaters use up much less space than tanks - often about as much as a typical electrical breaker box. They're better for the environment because they last longer and don't produce a rusty tank that will eventually end up in a landfill.

Tankless heaters tend to last longer than tanks, and they require less maintenance. Like tanks, they need to be flushed once a year to get rid of sediment and mineral buildup, but the procedure is much simpler. Because of this lifespan, they usually have a longer warranty.

One other advantage: When they break down, you won't have an issue with spilling an entire tankful of water on the floor.

Many tankless heaters qualify for a $300 federal tax credit if installed before the end of 2021. Some states, localities and utility companies offer benefits for installing tankless systems. Make sure you ask your installer what might be available to you.

The biggest downside of a tankless heater is it costs much more to install than a tank. Typically, you'll pay $1,200-$3,200 for a tankless heater - around twice as much as a tank, depending on the size of your house. The units are generally in the same price range, but the engineering and installation to convert a tank system to tankless bumps up the cost quite a bit.

Depending on your home's electrical infrastructure, you may pay even more for the necessary power connections for the heater.

You'll see an effect in your utility bills after you install a tankless heater, but it may not pay for itself for some years to come. The U.S. Department of Energy says you can expect an energy savings of $50-$100 per year.

If your primary concern is convenience as opposed to energy use, consider installing point-of-use tankless heaters on individual appliances. They're relatively easy to install and cost $100-$300 each. They can heat up water more quickly and the water only has to travel a short distance. However, each one can only heat a single faucet, bathtub or appliance, so the cost will go up if you outfit the entire house.

You can also install a solar tankless heater, but it's the most expensive, averaging $3,000-$10,000 to install.

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