tankless/On-demand water heaters

On-demand water heaters provide hot water only as it is needed, without the energy losses associated with a storage tank. But are they advantageous enough?

Types of Tankless water heaters

Besides the standard on-demand units it is now available a new category of water heaters, using the so-called condensing technology (which can be tankless or storage). Condensing models are more powerful but are also more expensive. Tankless Water Heater Anatomy

See: Condensing water heaters and Water heaters and prices

**How Demand Water Heaters Work**

Right (from Energy Star): Tankless Water Heater

The functioning of a demand/tankless water heater is particularly simple. When a hot water tap is turned on, cold water is driven through a pipe into the water-heater where a burner (or an electric element) heats the water.

With a tankless water heater people do not need to wait for a storage tank to fill up. It delivers a constant supply of hot water...

Advantages of tankless water heaters

Qualified tankless water heaters may save around $100 per year on gas bills, compared to common storage models (Energy Star estimates for average households).

They ensure continuous hot water whenever you need it, they may save significant space compared to common tank-type models, and they have a longer life expectancy (20 years or more) and less risks of damage and maintenance.

Disadvantages of tankless water heaters

Common tankless water heaters cost more than qualified storage models ($300 or $400 more) and may also demand higher installation costs (if you have an old tank-storage model).

See: Water Heaters Prices

The size

When buying a tankless/on-demand water heater, take into account its size. The number of simultaneous showers and other uses (washing machine, dishwasher) should be considered as well as - in some cases - the air-space heating of the rooms. Manufacturers present different models, for different needs.

Water heaters and solar water heating

Tankless heaters can be linked to solar-based systems to boost the water heating in periods of poor solar light.

They can be designed as a backup to preheated water produced by a compatible solar water heater (manufacturers like Bosch, GE/Rheem, Rinnai and others have such models). In this case, the burners will turn off when the preheated water is at the desired temperature.

The ignition system

Some new on-demand models incorporate new ignition system, allowing the unit to operate without a standing pilot, or a battery, or electricity. This issue is no more a limitation of tankless water heaters, and increases their efficiency. Just make sure you buy the right model, incorporating this new technological improvement.

Older models, with a constant burning pilot light can waste much more energy.

Installation and Maintenance

Proper installation of the water heater is important. It isn’t only a question of efficiency. Installation will also prevent safety problems. Have a qualified heating contractor and plumber to install your water heater.

Warranties and life expectancy

Tankless water heaters have a long lifespan, often more than 20 years. And they do not pose problems with replaceable parts. Warranties of 6-10 (or more) years are common.