FAQs

What are tankless water heaters?

Tankless water heaters are small household appliances that heat your water right as you are using it and then turn off. They run on gas -- both natural gas and propane (LP) models are sold -- or on electricity. They come in various sizes, from tiny units to use with one appliance to whole-house systems.

Are these the same as on-demand hot water heaters?

Yes, and they are also called also called on-demand, flash or instant water heaters.

What are the advantages of using tankless water heaters instead of conventional ones?

  • Tankless heaters use less energy. Because there is no storage tank, there isn't the heat loss associated with one.
  • You get continuous hot water that won't run out.
  • They typically last many years longer than conventional water heaters, and if they eventually have problems, they can often be repaired.
  • They are small in size, and can be hung on walls or in vented closets.

What disadvantages are there to using them?

  • The initial setup is more expensive than using a conventional tank water heater: the equipment itself can cost over twice what a tank heater would cost, plus you may need to upgrade your gas or electric input, which usually requires a professional to do it. (Gas installations will require a vent and possible renovation of your gas lines to be large enough. Electric installations may require some re-wiring.)
  • If you have a large household, you may not have enough hot water. Some families install two units to get around this.
  • In a whole-house installation, if the heater is some distance from the kitchen, bathroom, or laundry room, there will be a delay before you get hot water. Some people are really bothered by wasting the cold water.
  • In cold climates, where the water coming into your house is quite cold in the winter, many tankless heaters may not be able to produce enough hot water for a satisfying shower. The reason is that if the incoming water is colder, it has to be heated more to reach the desired temperature. If the heating element isn't sized large enough to do this easily, then you may (1) have water at the temperature you want -- but only a trickle of it at a time, or (2) enough water flowing but not as hot as you would like. (Generally, people in milder climates seem to be more content with their tankless hot water than people further north.)
  • You do have to get used to a different way of doing things. For example, if you are washing some dishes by hand and are used to turning the hot water off and on as you rinse, the water will be cold for a bit each time you turn the faucet on.
  • All tankless hot water heaters have minimum flow rates, so if you have the habit of washing dishes with a very small trickle of hot water running to rinse as you go, this won't be possible.

How do I tell what size heater to get?

This depends on how much hot water you need at one time. If there will be more than one person taking showers at the same time, this will require a larger unit than if you can take showers one person after another.

By the same token, the time that you intend to run a dishwasher or washing machine is also important in sizing your unit. If there are one or two people in your family, and you can do all these things just one at a time, a much smaller unit will serve you than if your family needs to do two or more things simultaneously.

Check the manufacturer's descriptions closely, and if you live in a cold climate, take them with a grain of salt.

How much energy will I save compared to a tank heater?

Estimates vary on this, but everyone agrees that gas tankless water heaters are considerably more efficient than electric. The U.S. Department of Energy says you can save up to 30% compared to a tank heater, but there are also estimates by other groups that tankless hot water heaters will save you between 8% and 20% of the energy that a tank system requires. Some of the manufacturers claim savings of up to 50%.

Which tankless water heaters are best?

Gas or Electric?

If you can, get a gas tankless water heater, either for natural gas or propane. They are more expensive to purchase and install, but your monthly bills will be less -- and see my page about tax credits for tankless water heaters, which only applies to gas ones.

It's worth noting that large electric units can require more power from the grid at peak hours, thus paradoxically requiring the electric company to produce more energy, not less. See "Environment" articles on this website for more about this.

Which Brands Are Best?

For gas tankless water heaters, Noritz seems to be the top of the line. Takagi has a lot of satisfied customers. Rinnai, Rheem (made by Paloma), and Bosch follow in roughly that order. The main dissatisfaction I read about Bosch was regarding their customer service.

Of course, opinions vary, and as I researched forums and discussions online, I would often see someone say that they loved a particular brand and model, while someone else couldn't say enough bad about the same unit.

It was noteworthy that more than half of the complaints were directly related to the way tankless heaters work, rather than to specific flaws in the units.

I have not yet researched electric units enough to have formed an opinion, but I did notice that on eBay, the Titans sell very well.

Personal Opinion: If I were buying a unit today, personally I would check prices on the Noritz line -- and probably go with a Takagi if Noritz was beyond my budget.