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Tankless water heaters

Tankless pros and cons
If you're building a new home, you can have instantaneous hot water - with no bulky tank to install or maintain.
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Tankless water heaterHave you ever had a blast of cold water in the shower because the hot water ran out? With a tankless water heater, you can have a virtually endless supply of hot water – and lower energy bills.

How it works

Tankless water heaters – also called as “instantaneous” or “on demand” water heaters – consist of an electric or gas heating element enclosed in a small module. Instead of warming a large amount of water stored in a tank, a tankless unit heats only the water that flows through it.

When you turn on the hot water faucet, the module senses the change in flow and pressure, and the heating element immediately switches on. Shut off the faucet, the heater stops immediately.

A “whole-house” tankless water heater is much smaller than a tank water heater, taking up only two or three cubic feet of space. Smaller “point-of-use” water heaters can be installed directly below a faucet, inside a bathroom or kitchen cabinet.

Tankless water heater - diagram

Newer on-demand water heaters also have digital temperature controls with sensors that check the water temperature more than 7,000 times each day.

The benefits

The energy savings with this technology can be significant. With conventional water heaters, up to 20 percent of the energy used is wasted because of “standby” heat loss from the tank and hot water pipes.

Tankless water heater - heating elementTankless models eliminate these losses, resulting in an energy factor of 0.84, compared to 0.64 for the most energy-efficient tank-style water heater.

That means replacing a natural gas tank water heater with a tankless model will cut operating costs by 25 to 45 percent. The savings are even more dramatic if you replace an electric or liquid propane water heater – you’ll cut your water heating costs by 50 percent or more!

Some older tankless heaters allowed the water temperature to vary depending on the amount of water being used. Newer models have modulating gas valves or sequential electric elements that produce more heat as water flow increases.

Maintenance costs are another bonus: Tankless heaters have a lifespan up to twice as long as conventional units, because there is no tank to rust or anode rod to replace.

The drawbacks

The biggest drawback to a tankless water heater is the price, averaging around $1,300 for the unit itself. This technology also requires larger gas lines, different exhaust vents and water treatment, creating additional installation expense.

For that reason, tankless water heaters aren’t cost-effective for an existing home. But in a newly-constructed home, you can expect to have your investment paid back in energy savings in about five to seven years.

Another consideration is the maximum flow rate – if you have a large family, you might not have enough capacity to take two showers and run the clothes washer and dishwasher simultaneously. You can avoid those problems by running appliances late at night.

Are you an Alliant Energy customer?

If you’re an Alliant Energy utility customer in Iowa or Wisconsin, you can earn cash back when you purchase a new high-efficiency water heater.

And don't forget to use Alliant Energy’s online Dealer Locator to find energy-smart plumbing experts in your area.

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If you are vision-impaired or have some other disability under the Americans with Disabilities Act or a similar law, and you wish to discuss potential accommodations related to shopping or ordering on or using the benefits of our website, please contact Alliant Energy at 1-800-ALLIANT (800-255-4268).