[LazyPup]

The original question was relating to replacing an electric tank type water heater with an “on demand tankless water heater” and I pointed out that in many cases it would require upgrading the house electrical service entrance equipment. It must be mentioned that the same is true of retrofitting an existing structure with a gas type tankless. Although a tankless water heater does not consume energy during periods of non- use, it must be understood that the energy requirements when firing are extremely high. Typically a gas tankless requires the same amount of natural gas, as would a gas furnace. In many instances in order to provide the necessary gas we have to increase the size of the entire gas line from the municipal main to the structure. From this you can easily see that retrofitting an existing structure with a tankless water heater can pose a number of rather expensive problems.

I also pointed out that while a tankless may be rated high enough to provide the total gallon per minute demand of your house, that rating is the maximum rating when the incoming water is at the natural geothermal ground temperature of 50-55degF, however in the colder northern climates the rate of flow will diminish as the incoming water temperature drops.

In all fairness to the tankless technology it must be mentioned that if you are building a new house you will be initially installing the electrical or gas service, and in this instance increasing the size of the electrical equipment or gas line would only present a small increase to overall cost of installing the service.

If you are building a new home in the sunbelt where the incoming water will always be at the natural geothermal temperature of 50-55 or higher from warmer surface soil temperatures a tankless water heater might offer a good alternative.

One of the downsides of a tankless system is that most of them cannot support the minimal rate of flow required to maintain a circulating hot water loop to provide instant on hot water. This problem can be easily overcome by installing a small 2 or 3gallon electric water heater immediately downstream of the tankless, we can then connect the return line of the loop back to the small tank. In this manner the small tank can provide the necessary hot water to keep the loop functioning.