Tankless Water Heaters
posted in Cool Products, How to, Water Heaters |Tankless (a.k.a. demand or instantaneous) water heaters provide hot water only as it is needed instead of continuously heating a reserve tank of water as with conventional water heaters.
The basics of how they work:
1) Water enters the heater. 
2) A water flow sensor detects the water flow.
3) The computer automatically ignites the burner.
4) The water circulates through the heat exchanger (coil).
5) The heat exchanger instantly heats the water at the designated temperature
(this takes only 5 seconds).
6) The heater can provide you with endless hot water continuously.
7) When the hot water tap is turned off, the unit shuts down automatically.
Types:
- Electric Tankless Water Heater
- Gas-Fired Tankless Water Heater
PROS and CONS:
PRO: Endless hot water. Since there is no tank to fill, there is no end to your supply of hot water.
CON: If too many people (or appliances) are using water then there may not be enough hot water AT THAT MOMENT. Some homeowners install more than one to prevent this from happening.
PRO: Space saving & easy installation. A standard tankless water heater, taking up only 2.2 cubic feet of space & 60 pounds, is about the size of a suitcase. This allows for installation in spaces with limited area or even outdoors with no enclosures.
CON: The heat exchanger inside a tankless water heater requires periodic descaling in hard-water areas, using a mild acid liquid, but the service life of the unit should be 20 years or more.
PRO: Money & energy savings. Since a tankless water heater has neither a storage tank to keep heated all day, nor a pilot light, it burns energy only when you need hot water. This eliminates standby heat loss, which can be as high as 3-4% every hour for storage tank type water heaters.
CON: Flow rate. A quirk about tankless water heaters is that they require a certain flow rate through the unit in order to activate the switch that turns on the burner. Unless you’re using a half gallon of water per minute, the burner won’t fire, and you won’t get any hot water.
Installation:
It can get complicated, and that’s why installing a tankless water heater, while beneficial from an energy-efficiency standpoint in most cases, needs to be thought through carefully, and it is probably not an ideal do-it-yourself project.
If you decide to look further into installing a tankless water heater, be aware that you will likely have to deal with some gas piping, fluepipe, and electrical issues.
For more information on tankless water heaters you can visit the the U.S. Department of Energy Consumer Guide page.
