Natural Gas Tankless Water Heaters: Are They Right for You?

There are many different advantages to switching from a tanked to a tankless heater. Paramount among these reasons is the amount of energy savings involved when you can successfully switch from a traditional hot water heater to a tankless model. It is estimated that 14%-25% of household energy consumption (whether electric or gas) is used for heating water.

With a traditional hot water heater, you are spending energy keeping a reservoir of water heated at the desired temperature at all times-even when the water is not in use. So if for some reason you do not need hot water (such as while on vacation, at school, work, etc.) you are still spending resources to keep that water ready at a moments notice.

Advantages of Using Tankless Water Heaters

This is where the advantage of having a tankless heater first appear. A tankless heater only heats water when a faucet is turned on, thus eliminating the waste involved in keeping a reservoir of water hot. Tankless heaters are also small enough that you can place them under vanities or closer to the point of service for smaller demands. If you have a water outlet located far away from your central water heater, in order to save on waste (for example, a pipe 25 feet long and ¾ inch in diameter will hold approximately 1.6 gallons of water) you could place a tankless heater at the point of service. That is a gallon and a half that you have to let go down the drain before you get hot water, and a gallon and a half that is sitting in the pipe cooling when you shut the water off. By making use of point of service units, you can cut your waste, therefor cutting your expenses, dramatically.

Considerations About Natural Gas Tankless Water Heaters

Before rushing out to buy one of these modern marvels, there are a few calculations and details you will need to work out. While it is easy to do some of the calculations on your own, unless you are knowledgeable about the volumetric pressure of natural gas, it is best to have a professional evaluate your overall plan once decided upon.

First, how many GPM (gallons per minute) do you need? The best way to calculate this is to find the item with the most GPM need. Lets say that it is your shower and the shower head that you have installed is rated for 2.5 GPM-then you would need this output as a minimum, preferably more. On this same line, be sure to read the fine print and reviews before purchasing a model based on the GPM output labeled on the box. Gas tankless heaters adjust temperature two ways-increasing the flame height and slowing the water down (decreasing pressure). If you have your flame turned all the way up, and the box says 4.3 GPM, usually that is with the pressure all the way up. Since the water may not get as hot as you like (because it travels through the heat exchange too fast), you may have to slow it down considerably. For example, on a model that we helped install the 4.3GPM did not provide a warm enough water. Once we adjusted the pressure to slow the water down (letting it stay in the heat exchange longer) our average output dropped to 3.7GPM.

Also, decide if you will be using hot water at any given time on more than one device. The specifications of the brand and model you are choosing will tell you if it is rated for more than one output at a time. Conversely, if you are going to run more than one faucet or utility at a time, be sure to calculate the GPM needed for the potential needed output for all outlets that could be open simultaneously.

Once you have decided on the size of system you want, it is time to look at the details of installation. After you have picked the area you want your natural gas tankless water heater installed, it must be vented in most cases. This vent either has to go vertically through the roof, or if vented through a side wall it must have and exhaust kit (which in our case was as much as the heater at $417). Also, your heater will have a minimum BTU load that is needed to sustain proper heat. Each appliance that you have on your natural gas line has a recommended BTU load-so if you have a dryer, stove, furnace, etc., you must have a large enough black iron natural gas line to allow this amount of gas to flow freely. For example, 35 feet of ¾ inch line can only carry slightly above 130,000 BTU. Make sure to calculate if you can add your natural gas tankless water heater to your existing line, or figure the cost of dedicating a line when you install.

Good luck, and we hope you have endless hot water!

"Installing a Natural Gas Tankless Water Heater" Contractormag.com

"Water Heaters" Energy.gov

Tanklesswaterheaterguide.com Tankless Water Heater Guide