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Tankless Water Heaters

Tankless water heating is a different approach to heating water for domestic use. The general idea for tankless water heating is that instead of heating a large quantity of stored water over a long time, a very small quantity of water is heated on demand. This water is heated so quickly that it can be heated in the pipe as it is flowing to the point of usage. These systems are very efficient as they are simply heaters being "cooled" by flowing water. There are a few issues to consider when choosing a tankless system. The two controlling factors are the flow rate, or how fast water needs to come out of the pipe, and temperature rise, how much heat needs to be added to the water. These two factors determine the amount of electrical power that will be consumed when hot water is needed.

The nature of an on demand hot water system is that the power usage is also on demand. While this means there is no “stand-by” losses, the on demand power requirements can be quite high. In the case of a solar powered house, these momentary power demands may be exceedingly high to be practical. In addition to high line currents, most tankless systems operate on 208 or 240 Volt AC source which may not be available from the house’s inverters.

On the bright side, there is a $300 tax credit for tankless water system users. There is also a compromise available between tankless system and full tank systems. The “mini-tank” system heats a small quantity of water quickly in a small tank for later use. This is different from a full tank system in that the stand-by losses are minimized by storing less hot water. These systems consume less on demand power and operate on a standard 120V 10A power source.


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